Archive for the ‘Somatic Stem Cells’ Category

Mosaic (genetics) – Wikipedia

Somatic Stem Cells | Posted by admin
Mar 08 2019

In genetics, a mosaic, or mosaicism, involves the presence of two or more populations of cells with different genotypes in one individual who has developed from a single fertilized egg.[1][2] Mosaicism has been reported to be present in as high as 70% of cleavage stage embryos and 90% of blastocyst-stage embryos derived from in vitro fertilization.[3]

Genetic mosaicism can result from many different mechanisms including chromosome non-disjunction, anaphase lag, and endoreplication.[3] Anaphase lagging is the most common way by which mosaicism arises in the preimplantation embryo.[3] Mosaicism can also result from a mutation in one cell during development in which the mutation is passed on to only its daughter cells. Therefore, the mutation is only going to be present in a fraction of the adult cells.[2]

Genetic mosaics may often be confused with chimerism, in which two or more genotypes arise in one individual similarly to mosaicism. However, in chimerism the two genotypes arise from the fusion of more than one fertilized zygote in the early stages of embryonic development, rather than from a mutation or chromosome loss.

Different types of mosaicism exist, such as gonadal mosaicism (restricted to the gametes) or somatic mosaicism.

Somatic mosaicism occurs when the somatic cells of the body are of more than one genotype. In the more common mosaics, different genotypes arise from a single fertilized egg cell, due to mitotic errors at first or later cleavages.

In rare cases, intersex conditions can be caused by mosaicism where some cells in the body have XX and others XY chromosomes (46, XX/XY).[4][5] In the fruit fly Drosophila melanogaster, where a fly possessing two X chromosomes is a female and a fly possessing a single X chromosome is a sterile male, a loss of an X chromosome early in embryonic development can result in sexual mosaics, or gynandropmorphs.[6][7] Likewise, a loss of the Y chromosome can result in XY/X mosaic males.[8]

The most common form of mosaicism found through prenatal diagnosis involves trisomies. Although most forms of trisomy are due to problems in meiosis and affect all cells of the organism, there are cases where the trisomy occurs in only a selection of the cells. This may be caused by a nondisjunction event in an early mitosis, resulting in a loss of a chromosome from some trisomic cells.[9] Generally this leads to a milder phenotype than in non-mosaic patients with the same disorder.

An example of this is one of the milder forms of Klinefelter syndrome, called 46/47 XY/XXY mosaic wherein some of the patient's cells contain XY chromosomes, and some contain XXY chromosomes. The 46/47 annotation indicates that the XY cells have the normal number of 46 total chromosomes, and the XXY cells have a total of 47 chromosomes.

Around 30% of Turner's syndrome cases demonstrate mosaicism, while complete monosomy (45, X) occurs in about 5060% of cases.

But mosaicism need not necessarily be deleterious. Revertant somatic mosaicism is a rare recombination event in which there is a spontaneous correction of a mutant, pathogenic allele.[10] In revertant mosaicism, the healthy tissue formed by mitotic recombination can outcompete the original, surrounding mutant cells in tissues like blood and epithelia that regenerate often.[10] In the skin disorder ichthyosis with confetti, normal skin spots appear early in life and increase in number and size over time.[10]

Other endogenous factors can also lead to mosaicism including mobile elements, DNA polymerase slippage, and unbalanced chromosomal segregation.[11] Exogenous factors include nicotine and UV radiation.[11] Somatic mosaics have been created in Drosophila using Xray treatment and the use of irradiation to induce somatic mutation has been a useful technique in the study of genetics.[12]

True mosaicism should not be mistaken for the phenomenon of Xinactivation, where all cells in an organism have the same genotype, but a different copy of the X chromosome is expressed in different cells. The latter is the case in normal (XX) female mammals, although it is not always visible from the phenotype (like it is in calico cats). However, all multicellular organisms are likely to be somatic mosaics to some extent.[13]

Somatic mutation leading to mosaicism is prevalent in the beginning and end stages of human life.[11] Somatic mosaics are common in embryogenesis due to retrotransposition of L1 and Alu transposable elements.[11] In early development, DNA from undifferentiated cell types may be more susceptible to mobile element invasion due to long, un-methylated regions in the genome.[11] Further, the accumulation of DNA copy errors and damage over a lifetime lead to greater occurrences of mosaic tissues in aging humans. As our longevity has increased dramatically over the last century, our genome may not have had time to adapt to cumulative effects of mutagenesis.[11] Thus, cancer research has shown that somatic mutations are increasingly present throughout a lifetime and are responsible for most leukemia, lymphomas, and solid tumors.[14]

Genomic mosaiscism arises in developing and in adult brain cells leading to diverse, seemingly random, genomic changes.[15] A frequent type of neuronal genomic mosaicism is copy number variation. Possible sources of such variation were suggested to be incorrect repair of DNA damages and somatic recombination.[15][16]

One basic mechanism which can produce mosaic tissue is mitotic recombination or somatic crossover. It was first discovered by Curt Stern in Drosophila in 1936. The amount of tissue which is mosaic depends on where in the tree of cell division the exchange takes place. A phenotypic character called "Twin Spot" seen in Drosophila is a result of mitotic recombination. However, it also depends on the allelic status of the genes undergoing recombination. Twin spot occurs only if the heterozygous genes are linked in repulsion i.e. trans phase. The recombination needs to occur between the centromere the adjacent gene. This gives an appearance of yellow patches on the wild type background in Drosophila. another example of mitotic recombination is the Bloom's syndrome which happens due to the mutation in the blm gene. The resulting BLM protein is defective. the defect in RecQ an helicase facilitates the defective unwinding of DNA during replication and is thus associated with the occurrence of this disease.[17][18]

Germline or gonadal mosaicism is a special form of mosaicism, where some gametesi.e., sperm or oocytescarry a mutation, but the rest are normal.[19][20]

The cause is usually a mutation that occurred in an early stem cell that gave rise to all or part of the gametes.

This can cause only some offspring to be affected, even for a dominant disease.

Genetic mosaics can be extraordinarily useful in the study of biological systems, and can be created intentionally in many model organisms in a variety of ways. They often allow for the study of genes that are important for very early events in development, making it otherwise difficult to obtain adult organisms in which later effects would be apparent. Furthermore, they can be used to determine the tissue or cell type in which a given gene is required and to determine whether a gene is cell autonomous. That is, whether or not the gene acts solely within the cell of that genotype, or if it affects the entire organism of neighboring cells which do not themselves contain that genotype.

The earliest examples of this involved transplantation experiments (technically creating chimeras) where cells from a blastula stage embryo from one genetic background are aspirated out and injected into a blastula stage embryo of a different genetic background.

Genetic mosaics are a particularly powerful tool when used in the commonly studied fruit fly, where specially-selected strains frequently lose an X[7] or a Y[8] chromosome in one of the first embryonic cell divisions. These mosaics can then be used to analyze such things as courtship behavior,[7] female sexual attraction,[21] and the autonomy or non-autonomy of particular genes.

Genetic mosaics can also be created through mitotic recombination. Such mosaics were originally created by irradiating flies heterozygous for a particular allele with X-rays, inducing double-strand DNA breaks which, when repaired, could result in a cell homozygous for one of the two alleles. After further rounds of replication, this cell would result in a patch, or "clone" of cells mutant for the allele being studied.

More recently the use of a transgene incorporated into the Drosophila genome has made the system far more flexible. The flip recombinase (or FLP) is a gene from the commonly studied yeast Saccharomyces cerevisiae which recognizes "flip recombinase target" (FRT) sites, which are short sequences of DNA, and induces recombination between them. FRT sites have been inserted transgenically near the centromere of each chromosome arm of Drosophila melanogaster. The FLP gene can then be induced selectively, commonly using either the heat shock promoter or the GAL4/UAS system. The resulting clones can be identified either negatively or positively.

In negatively marked clones the fly is transheterozygous for a gene encoding a visible marker (commonly the green fluorescent protein or GFP) and an allele of a gene to be studied (both on chromosomes bearing FRT sites). After induction of FLP expression, cells that undergo recombination will have progeny that are homozygous for either the marker or the allele being studied. Therefore, the cells that do not carry the marker (which are dark) can be identified as carrying a mutation.

It is sometimes inconvenient to use negatively marked clones, especially when generating very small patches of cells, where it is more difficult to see a dark spot on a bright background than a bright spot on a dark background. It is possible to create positively marked clones using the so-called MARCM ("mosaic analysis with a repressible cell marker", pronounced [mark-em]) system, developed by Liqun Luo, a professor at Stanford University, and his post-doc Tzumin Lee who now leads a group at Janelia Farm Research Campus. This system builds on the GAL4/UAS system, which is used to express GFP in specific cells. However a globally expressed GAL80 gene is used to repress the action of GAL4, preventing the expression of GFP. Instead of using GFP to mark the wild-type chromosome as above, GAL80 serves this purpose, so that when it is removed by mitotic recombination, GAL4 is allowed to function, and GFP turns on. This results in the cells of interest being marked brightly in a dark background.[22]

In 1929, Alfred Sturtevant studied mosaicism in Drosophila.[6] A few years later, In the 1930s, Curt Stern demonstrated that genetic recombination, normal in meiosis, can also take place in mitosis.[23][24] When it does, it results in somatic (body) mosaics. These are organisms which contain two or more genetically distinct types of tissue.[25] The term "somatic mosaicism" was used by C.W. Cotterman in 1956 in his seminal paper on antigenic variation.[11]

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Mosaic (genetics) - Wikipedia

What is the Difference Between Embryonic and Somatic Stem Cells

Somatic Stem Cells | Posted by admin
Feb 27 2019

Themain differencebetween embryonic and somatic stem cells is that the embryonic stem cells are pluripotent whereas the somatic stem cells are multipotent.That means; the embryonic stem cells can become all types of cells in the body while somatic stem cells can differentiate into several types of cells, but not all.

Embryonic and somatic stem cells are two types of stem cells that occur during the lifetime of animals. Furthermore, embryonic stem cells occur in the inner cell mass of the embryo while somatic stem cells occur in most of the organs of the body including bone marrow, skin, skeletal muscles, liver, etc.

1. What are Embryonic Stem Cells Definition, Potency, Differentiation 2. What are Somatic Stem Cells Definition, Potency, Differentiation 3. What are the Similarities Between Embryonic and Somatic Stem Cells Outline of Common Features 4. What is the Difference Between Embryonic and Somatic Stem Cells Comparison of Key Differences

Embryonic Stem Cells, Multipotent, Pluripotent, Somatic Stem Cells, Three Germ Layers

Embryonic stem cells are the cells in the early stages of the embryo. The zygote, which is the conceptus of fertilization, divides by mitosis, forming the morula. After 5-6 days of fertilization, the morula develops into the blastocyst that contains two parts; thetrophoblastand the inner cell mass. Thetrophoblastis the outer layer of the embryo, which contains cells that develop into the placenta and umbilical cord. Here, the cells in the inner cell mass are pluripotent and are capable of differentiating into any type of cells in the body.

Figure 1: Stem Cell Differentiation

Moreover, they differentiate into the cells in the three germ layers; ectoderm, endoderm, and mesoderm. The cells in the three germ layers are multipotent stem cells that can differentiate into a particular group of cells in our body. Therefore, the cells in the ectoderm differentiate into the epidermis, lens of the eye, sebaceous glands, hair, nails, toothenamel, etc. In addition, the cells in mesoderm differentiate into muscle, bones, connective tissue, cartilage, adipose tissue, circulatory and the lymphatic system, dermis,notochord, etc. Furthermore, the cells in the endoderm differentiate into the stomach, colon, liver, bladder, pancreas, lungs, etc.

Somatic stem cells are the adult stem cells that occur inside the specialized tissues including bone marrow, skin, skeletal muscles, brain, liver, pancreas, dental pulp, etc. Furthermore, these cells are multipotent and can only differentiate into the several types of functionally-related cells that belong to the tissue of origin of the stem cells. Therefore, they continuously divide to produce new cells. A part of these new cellsdifferentiatesinto the functionally-specialized cells in that tissue and the rest of the cells renew the existing stem cell population.

Figure 2: Stem Cell Uses

For example, dividing hematopoietic stem cells in the bone marrow differentiate into the cells in the blood including red blood cells, white blood cells, and platelets. In addition, the stem cells in the bone marrow are the most studied type of somatic stem cells in the human body. However, somatic stem cells are difficult to identify, purify, and grow in cultures. Therefore, these stem cells are rarely subjected to the studies.

Embryonic stem cells refer to the stem cells derived from the undifferentiated inner mass cells of a human embryo while somatic stem cells refer to the undifferentiated cells found throughout the body that divide to replenish dying cells and regenerate damaged tissues. This is the basic difference between embryonic and somatic stem cells.

Embryonic stem cells occur in the three germ layers of the embryo while somatic stem cells occur in most of the body organs including skeletal muscles, bone marrow, skin, liver, etc.

Potency isthe main difference between embryonic and somatic stem cells. Embryonic stem cells are multipotent. That is; they can differentiate into any cell type in the body. In contrast, somatic stem cells are pluripotent. That is; they can differentiate only into several types of cells in the body, but not all types.

Embryonic stem cell studies are less known while somatic stem cell studies are well known. This is another difference between embryonic and somatic stem cells.

Embryonic stem cells are the stem cells in the inner cell mass of the embryo. Moreover, these cells are multipotent and they can differentiate into any type of cells in the body. On the other hand, somatic stem cells are the stem cells in the adult body organs. These cells can only differentiate into several types of cells in that organ, helping to replenish the damaged or aged cells. Therefore, the main difference between embryonic and somatic stem cells is the potency.

1.Stem Cell Basics V.National Institutes of Health, U.S. Department of Health and Human Services,Available Here

1. 422 Feature Stem Cell new By OpenStax College Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia 2. Stem cell treatments By Hggstrm, Mikael (2014). Medical gallery of Mikael Hggstrm 2014. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.008. ISSN 2002-4436 (Public Domain) via Commons Wikimedia

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What is the Difference Between Embryonic and Somatic Stem Cells

Somatic Cells – Definition and Examples | Biology Dictionary

Somatic Stem Cells | Posted by admin
Nov 14 2018

Somatic Cells Definition

Somatic cells are any cell in the body that are not gametes (sperm or egg), germ cells (cells that go on to become gametes), or stem cells. Essentially, all cells that make up an organisms body and are not used to directly form a new organism during reproduction are somatic cells. The word somatic comes from the Greek word (soma), which means body. In the human body, there are about 220 types of somatic cells.

There are many different kinds of somatic cells in the human body because nearly every cell found inside and on the surface of the human body, with the exception of cells that become sperm and eggs, is a somatic cell. In addition, mammals have many organ systems that specialize in specific functions, so there are many different specialized cells. The following is an overview of a few main types of cells in the human body.

Old bone cells are constantly being replaced with new bone cells. The two broad categories of bone cells are called osteoblasts and osteoclasts. Osteoblasts form bone and help maintain it. They are cuboidal, or square-shaped, and they make proteins that form bone. They also communicate with each other and produce certain molecules such as growth factors, which promote bone growth. Osteoclasts, on the other hand, resorb, or dissolve, old bone. They are large cells that have multiple nuclei. When the work of an osteoblast or osteoclast is done, it undergoes a programmed cell death known as apoptosis.

Muscle cells are also known as myocytes. They are long, tube-shaped cells. There are three types of muscle which are each made up of specialized myocytes: smooth muscle, cardiac muscle, and skeletal muscle. Smooth muscle lines the walls of internal organs such as the bladder, uterus, and digestive tract. Cardiac muscle is only found in the heart, and it allows the heart to pump blood. Skeletal muscle is attached to bone and helps move the body.

The various parts of myocytes have special terminology because myocytes are so different from other types of cells. The cell membrane is called the sarcolemma, the mitochondria are called sarcosomes, and the cytoplasm is called the sarcoplasm. The sarcomere is the part of the cell that contracts and allows muscle movement, and they form long chains called myofibrils that run throughout each muscle fiber. Muscle cells cannot divide to form new cells. This means that even though muscles can get bigger through exercise, babies actually have more myocytes than adults.

Nerve cells are called neurons. Neurons are found throughout the body, but there is an especially high density in the brain and spinal cord, which control the bodys movements. Neurons send and receive information to and from other neurons and organs via chemical and electrical signaling. Neurons maintain a certain voltage, and when this voltage changes, it creates an electrochemical signal called an action potential. When an action potential occurs in a neuron, the neuron will release neurotransmitters, which are chemicals that affect target cells. Some examples of neurotransmitters are dopamine, serotonin, epinephrine (adrenaline), and histamine.

Neurons have a unique structure as shown in the diagram above. The main parts of a neuron are the soma, axon, and dendrites. The soma is the body of the cell and contains the nucleus. The axon is a long protrusion that transmits electrical impulses. The dendrites fan out from the soma and receive impulses from other neurons. The end of the axon branches out into axon terminals, which is where neurotransmitters are released.

Blood cells are called hematopoietic cells or hemocytes. There are three general types of blood cells: red blood cells, known as erythrocytes, white blood cells, or leukocytes, and platelets, also known as thrombocytes or yellow blood cells. These cells, along with plasma, comprise the contents of blood.

Erythrocytes carry oxygen to cells via the molecule hemoglobin, and they collect the waste product carbon dioxide from cells. They make up 40 to 45 percent of the bloods volume. Approximately one-fourth of the cells in the human body are erythrocytes. They live for around 100 to 120 days, and they do not have a nucleus when mature. Leukocytes defend the body against foreign substances and infectious disease agents like viruses and bacteria. They have a very short lifespan of only three to four days. Platelets are small cell fragments that help blood to clot after an injury. They also have a short lifespan, living for five to nine days.

Somatic cells are produced through the cell division process of mitosis. They contain two copies of each chromosome, one from an organisms mother and one from their father. Cells with two copies of each chromosome are called diploid. Sperm and egg cells, called gametes, are formed through meiosis, which is a slightly different cell division process that results in the cells having only one copy of each chromosome. These cells are called haploid. Gametes are haploid because a sperm and an egg fuse during fertilization to create a new organism with diploid cells. Mutations in somatic cells can affect an individual organism, but they do not affect the offspring since they are not passed on during reproduction. However, mutations that occur in gametes can affect offspring since the gametes are passed down. When gametes fuse, they become the offsprings first somatic cell, which subsequently divides to form all of their other somatic cells. Therefore, while mutations in somatic cells will not affect the next generation, mutations in gamete cells do and can sometimes have drastic effects. For example, if a large-scale mutation occurs and there is an extra chromosome in the fertilized egg, all the somatic cells will also have that extra chromosome when it divides. An extra chromosome 21 results in Down Syndrome.

1. Which type of cell is NOT a somatic cell? A. Leukocyte B. Myocyte C. Osteoblast D. Gamete

Answer to Question #1

D is correct. Gametes such as sperm and eggs are not somatic cells. They are germline cells, which are cells that pass on genetic material through the process of reproduction. Leukocytes (white blood cells), myocytes (muscle cells) and osteoblasts (a type of bone cell) are all somatic cells.

2. What is the approximate lifespan of an erythrocyte? A. 3-4 days B. 5-9 days C. 100-120 days D. 365-395 days

Answer to Question #2

C is correct. Erythrocytes, or red blood cells, live about 100-120 days, which is the longest lifespan of a blood cell. Leukocytes live for 3-4 days, while platelets live for 5-9 days.

3. What is the function of an osteoclast? A. To form and help maintain bone B. To attach to bone and allow it to move C. To resorb old bone D. To release neurotransmitters

Answer to Question #3

C is correct. Osteoclasts are bone cells that resorb, or break down, old bone so that osteoblasts can then replace it with newly created bone. Choice A describes osteoblasts. Choice C is referring to muscle cells, and choice D describes neurons.

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Somatic Cells - Definition and Examples | Biology Dictionary

Stem Cell Quick Reference – Learn.Genetics

Somatic Stem Cells | Posted by admin
Sep 09 2018

Are you confused about all the different types of stem cells? Read on to learn where different types of stem cells come from, what their potential is for use in therapy, and why some types of stem cells are shrouded in controversy.

Researchers are working on new ways to use stem cells to cure diseases and heal injuries. Learn more about unlocking stem cell potential.

Somatic stem cells (also called adult stem cells) exist naturally in the body. They are important for growth, healing, and replacing cells that are lost through daily wear and tear.

Stem cells from the blood and bone marrow are routinely used as a treatment for blood-related diseases. However, under natural circumstances somatic stem cells can become only a subset of related cell types. Bone marrow stem cells, for example, differentiate primarily into blood cells. This partial differentiation can be an advantage when you want to produce blood cells; but it is a disadvantage if you're interested in producing an unrelated cell type.

Most types of somatic stem cells are present in low abundance and are difficult to isolate and grow in culture. Isolation of some types could cause considerable tissue or organ damage, as in the heart or brain. Somatic stem cells can be transplanted from donor to patient, but without drugs that suppress the immune system, a patient's immune system will recognize transplanted cells as foreign and attack them.

Therapy involving somatic stem cells is not controversial; however, it is subject to the same ethical considerations that apply to all medical procedures.

Embryonic stem (ES) cells are formed as a normal part of embryonic development. They can be isolated from an early embryo and grown in a dish.

ES cells have the potential to become any type of cell in the body, making them a promising source of cells for treating many diseases.

Without drugs that suppress the immune system, a patient's immune system will recognize transplanted cells as foreign and attack them.

When scientists isolate human embryonic stem (hES) cells in the lab, they destroy an embryo. The ethical and legal implications of this have made some reluctant to support research involving hES cells. In recent years, some researchers have focused their efforts on creating stem cells that don't require the destruction of embryos.

Learn more about the controversy behind embryonic stem cells and why new stem-cell technologies may bring it to an end. The Stem Cell Debate: Is It Over?

Induced pluripotent stem (iPS) cells are created artificially in the lab by "reprogramming" a patient's own cells. iPS cells can be made from readily available cells including fat, skin, and fibroblasts (cells that produce connective tissue).

Mouse iPS cells can become any cell in the body (or even a whole mouse). Although more analysis is needed, the same appears to be true for human iPS cells, making them a promising source of cells for treating many diseases. Importantly, since iPS cells can be made from a patient's own cells, there is no danger that their immune system will reject them.

iPS cells are much less expensive to create than ES cells generated through therapeutic cloning (another type of patient-specific stem cell; see below). However, because the "reprogramming" process introduces genetic modifications, the safety of using iPS cells in patients is uncertain.

Therapy involving iPS cells is subject to the same ethical considerations that apply to all medical procedures.

Therapeutic cloning is a method for creating patient-specific embryonic stem (ES) cells.

Therapeutic cloning can, in theory, generate ES cells with the potential to become any type of cell in the body. In addition, since these cells are made from a patient's own DNA, there is no danger of rejection by the immune system.

In 2013, for the first time, a group of researchers used therapeutic cloning to make ES cells. The donor nucleus came from a child with a rare genetic disorder. However, the cloning process remains time consuming, inefficient, and expensive.

Therapeutic cloning brings up considerable ethical considerations. It involves creating a clone of a human being and destroying the cloned embryo, and it requires a human egg donor.

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Where Do Stem Cells Come From? –

Somatic Stem Cells | Posted by admin
Jul 02 2018

Stem cells are specialized cells that have the potential to develop into not one but many different types of cell. They are unlike any other cell for three specific reasons:

Currently, blood stem cells are the only type regularly used for treatment. In cases of leukemia or lymphoma, this type of cell is used in a procedure we commonly refer to as a bone marrow transplant. For this purpose, only adult stems cells are used.

When it comes to stem cell research, the cells may come from any number of different sources, including adult donors, embryos, or genetically altered human cells.

The cells of the bone marrow produce all of your healthy blood cells, including red blood cells, white blood cells, and platelets. Hematopoietic stem cells are those found in bone marrow that serves as the "parent" for all of these different types of cells.

Hematopoietic stem cells are transplanted into a person with cancer to help replenish bone marrow. The procedure is often used when high dose chemotherapy effectively destroys the existing stem cells in a persons bone marrow.

To remedy this, donated stem cells are injected into a vein and eventually settle in the bone marrow where they start producing healthy, new blood cells.

Years ago, the only source for hematopoietic stem cells were those taken from bone marrow. It was soon after discovered that many of these cells were circulating freely in the bloodstream.

In time, scientists learned how to harvest these cells from circulating blood and to transplant them directly into a donor.

This type of transplant known as a peripheral blood stem cell transplant, or PBSCT has become the more common procedure, although both methods are still used. PBSCT is far less invasive and doesnt require the removal of marrow from the hip bone.

Adult stem cells, called somatic stem cells, are derived from a human donor. Hematopoietic stem cells are the most widely known example. Scientists have found somatic stem cells in more tissues than was once imagined, including the brain, skeletal muscle, skin, teeth, heart, gut, liver, ovarian cells, and testis.

Embryonic stem cells are controversial since they are derived from human embryos that have either been destroyed or harvested for science. Embryonic stem cells were first grown in a laboratory in 1998 for reproductive purposes. Today, they are used primarily for research into treatments or cures for cancers, blindness, juvenile diabetes, Parkinsons, spinal cord injuries, and genetic disorders of the immune system.

Embryonic stem cells are pluripotent, meaning they are able to grow into the three types of germ cell layers that make up the human body (ectoderm, mesoderm, endoderm).

In other words, they can develop into each of the more than 200 cell types if specified to do so.

Induced pluripotent stem cells, or iPSCs, are somatic stem cells that have been genetically reprogrammed to be more like embryonic stem cells. iPSCs usually start out as skin or blood cells which then undergo genetic programming.

iPSCs were first developed in 2006 and pose one major advantage over somatic and embryonic stem cells: they can be made in a patient-matched manner. What this means is that a lab can tailor-make a pluripotent stem cell line individualized from a persons own cells or tissues.

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What Is Another Name for Somatic Stem Cells and What Do …

Somatic Stem Cells | Posted by admin
Jun 22 2018

Somatic stem cells are also referred to as adult stem cells. Unlike embryonic stem cells, somatic stem cells come from a fully developed human being. Somatic stem cells are somewhat specialized to produce certain kinds of cells. However, scientists are currently working on ways to increase their range of use in cutting-edge therapies.

Adult stem cells have been found in a wide range of organs and tissues, including bone marrow, blood vessel, brain, epithelium, heart, intestine, liver, ovary, skeletal muscle, skin, teeth, and testis.

While these cells are programmed to become a certain type of cell, they are still capable of differentiation. For example, bone marrow stem cells can differentiate into either red or white blood cells. While brain stem cells could form neurons or supporting brain cells, they would typically not become cell types found in other organs.

Somatic stem cells typically divide to form mature cell types that have the characteristics necessary to become a functional part of tissues or organs, a process called normal differentiation.

Certain types of somatic stem cells have been found to have the capacity to give rise to cell types for organs or tissues not in their lineage. For example, brain stem cells that differentiate into cardiac muscle cells. This phenomenon is called transdifferentiation.

Doctors performed the first bone marrow transplant in 1968. The procedure also marked the first medical use of somatic stem cells, as bone marrow cells can differentiate into red blood cells or white blood cells. Today bone marrow transplants are used to treat a range of ailments, from blood cancers to immune disorders.

In 2010, a biotech company called Neuralstem began conducting clinical trials for the use of spinal cord stem cells to treat Amyotrophic Lateral Sclerosis (ALS), also known as Lou Gehrigs Disease. The second phase of these trials was conducted in September 2013.

With embryonic stem cells, which are stem cells derived from fertilized human eggs, sparking an intense political and ethical debate, many researchers are turning to somatic stem cells as a less divisive alternative.

The problems is that embryonic stem cells can become any type of cell in the body -- while somatic cells are more restricted to a specific lineage. Embryonic stem cells are also more easily grown in culture, according to the National Institutes of Health.

However, because a patient's own cells can be used in a somatic stem cell treatment regimen -- they are thought to be less likely to cause a rejection after transplantation. The lack of a rejection response by the body's immune system would eliminate the need for immunosuppressive drugs, which often cause undesirable side effects.

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Difference Between Somatic Cells and Gametes …

Somatic Stem Cells | Posted by admin
Jun 19 2018

Somatic Cells vs Gametes

The most important structures in the cell during division are the chromosomes, which contain DNA. This is because they are responsible for the transmission of the hereditary information from one generation to the next. Cells in the body are of two types depending on the number of chromosomes present in the nucleus. The two types are somatic cells and gametes.

What are Somatic Cells?

A somatic cell is any cell other than a germline cell found in the body of a multicellular organism. These are diploid cells having two sets of chromosomes; one is maternal and the other is paternal. When considering one homologous pair, one chromosome is inherited from the mother, and the other is inherited from the father. For an example, a human somatic cell contains 46 chromosomes arranged in to 23 pairs in which one chromosome of each pair is maternal, and the other is paternal. Stem cells produced by mitosis undergo differentiation and give rise to different types of somatic cells, which intern form almost all the internal and external structures of the body.

What are Gametes?

Unlike the somatic cells, gametes are haploid cells, which carry unpaired chromosomes. A gamete of a particular multicellular organism always carries only half the number of chromosomes carried by a somatic cell of that particular organism. For an example, a human gamete contains only 23 chromosomes where as a human somatic cell contains 46 chromosomes. Germ cells are the cells which give rise to gametes. Meiosis takes place during gametogenesis (process of gamete production) giving rise to haploid cells. Haploid gametes fuse during sexual reproduction giving rise to a diploid zygote.

What is the Difference between Somatic Cells and Gametes?

Somatic cells are diploid cells, whereas the gametes are haploid cells.

Stem cells give rise to somatic cells, and germ cells give rise to gametes.

Meiosis does not take place during the production of somatic cells, whereas meiosis takes place during gametogenesis (production of gametes) giving rise to haploid cells.

Somatic cells contain homologous pairs of chromosomes, whereas gametes contain only unpaired chromosomes.

Somatic cells form internal and external structures of the body, whereas gametes do not.

Somatic cells are found almost everywhere in the body, whereas gametes are restricted to certain parts.

Somatic cells do not fuse during sexual reproduction, whereas gametes fuse during sexual reproduction giving rise to a diploid zygote.

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Skin graft gene therapy could treat obesity and diabetes – ResearchGate (blog)

Somatic Stem Cells | Posted by admin
Aug 03 2017

In a new study, researchers at the University of Chicago have provided proof of concept for a new form of gene therapy that is administered via a skin transplant. In the study, they treated type-2 diabetes and obesity in mice by inserting the gene for a glucagon-like peptide 1 (GLP1) that stimulates the pancreas to secrete insulin. The extra insulin can prevent diabetes complications by removing excessive glucose from the bloodstream. It can also delay gastric emptying and reduce appetite.

We spoke to one of the studys authors, Xiaoyang Wu, about the work.

ResearchGate: What motivated this study?

Xiaoyang Wu: We have been working on skin somatic stem cells for a long time. As one of the most studied adult stem cell systems, skin stem cells have several unique advantages as the novel vehicle for somatic gene therapy. For one, the system is well established. Human skin transplantation using a CEA device developed from skin stem cells has been used clinically for decades for burn wound treatment, and is proven to be safe and effective.

RG: Can you tell us what you achieved?

Xiaoyang Wu: We established a novel mouse to mouse skin transplantation system to test skin gene therapy. In the proof-of-concept study, we showed that we can achieve the systematic release of GLP1 at therapeutic concentration by engineered skin grafts.

RG: How does this work to treat obesity and diabetes?

Xiaoyang Wu: When engineered to express therapeutic hormones, such as GLP1, the skin grafts can be used to suppress body weight gain, and development of type 2 diabetes.

RG: What were some of the challenges in development? How did you overcome them?

Xiaoyang Wu: The mouse skin transplantation system has not been well established before. We circumvented the technical issues by building a novel skin organoid culture system in vitro.

RG: Are there alternate methods to delivery this type of therapy, and if so why is skin better?

Xiaoyang Wu: The GLP1 receptor agonist can be applied with an injection, but the half-life will be short. Skin based gene delivery provides a long term and safe way for drug delivery in vivo.

RG: Do think this would have a similar effect in humans?

Xiaoyang Wu: Our proof-of-concept work demonstrated its possible to use engineered skin grafts to treat many non-skin diseases. Clinical translation of our findings will be relatively easy, as skin transplantation in human patients has been well established and clinically used for treatment of burn wounds for many years.

RG: Whats next for your research?

Xiaoyang Wu: Before clinical translation, we will further characterize our mouse model of skin therapy, looking at potential immune reaction, stability of skin grafts, and duration of the therapeutic effects. We are also interested in using our mouse model to test other potential applications of skin gene therapy, such as human genetic diseases, including hemophilia and urea cycle disorders.

Featured image courtesy ofMehmet Pinarci.

The rest is here:
Skin graft gene therapy could treat obesity and diabetes - ResearchGate (blog)

Cloning – Wikipedia

Somatic Stem Cells | Posted by admin
Dec 07 2016

In biology, cloning is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments (molecular cloning), cells (cell cloning), or organisms. The term also refers to the production of multiple copies of a product such as digital media or software.

The term clone, invented by J. B. S. Haldane, is derived from the Ancient Greek word kln, "twig", referring to the process whereby a new plant can be created from a twig. In horticulture, the spelling clon was used until the twentieth century; the final e came into use to indicate the vowel is a "long o" instead of a "short o".[1][2] Since the term entered the popular lexicon in a more general context, the spelling clone has been used exclusively.

In botany, the term lusus was traditionally used.[3]:21, 43

Cloning is a natural form of reproduction that has allowed life forms to spread for more than 50 thousand years. It is the reproduction method used by plants, fungi, and bacteria, and is also the way that clonal colonies reproduce themselves.[4][5] Examples of these organisms include blueberry plants, hazel trees, the Pando trees,[6][7] the Kentucky coffeetree, Myricas, and the American sweetgum.

Molecular cloning refers to the process of making multiple molecules. Cloning is commonly used to amplify DNA fragments containing whole genes, but it can also be used to amplify any DNA sequence such as promoters, non-coding sequences and randomly fragmented DNA. It is used in a wide array of biological experiments and practical applications ranging from genetic fingerprinting to large scale protein production. Occasionally, the term cloning is misleadingly used to refer to the identification of the chromosomal location of a gene associated with a particular phenotype of interest, such as in positional cloning. In practice, localization of the gene to a chromosome or genomic region does not necessarily enable one to isolate or amplify the relevant genomic sequence. To amplify any DNA sequence in a living organism, that sequence must be linked to an origin of replication, which is a sequence of DNA capable of directing the propagation of itself and any linked sequence. However, a number of other features are needed, and a variety of specialised cloning vectors (small piece of DNA into which a foreign DNA fragment can be inserted) exist that allow protein production, affinity tagging, single stranded RNA or DNA production and a host of other molecular biology tools.

Cloning of any DNA fragment essentially involves four steps[8]

Although these steps are invariable among cloning procedures a number of alternative routes can be selected; these are summarized as a cloning strategy.

Initially, the DNA of interest needs to be isolated to provide a DNA segment of suitable size. Subsequently, a ligation procedure is used where the amplified fragment is inserted into a vector (piece of DNA). The vector (which is frequently circular) is linearised using restriction enzymes, and incubated with the fragment of interest under appropriate conditions with an enzyme called DNA ligase. Following ligation the vector with the insert of interest is transfected into cells. A number of alternative techniques are available, such as chemical sensitivation of cells, electroporation, optical injection and biolistics. Finally, the transfected cells are cultured. As the aforementioned procedures are of particularly low efficiency, there is a need to identify the cells that have been successfully transfected with the vector construct containing the desired insertion sequence in the required orientation. Modern cloning vectors include selectable antibiotic resistance markers, which allow only cells in which the vector has been transfected, to grow. Additionally, the cloning vectors may contain colour selection markers, which provide blue/white screening (alpha-factor complementation) on X-gal medium. Nevertheless, these selection steps do not absolutely guarantee that the DNA insert is present in the cells obtained. Further investigation of the resulting colonies must be required to confirm that cloning was successful. This may be accomplished by means of PCR, restriction fragment analysis and/or DNA sequencing.

Cloning a cell means to derive a population of cells from a single cell. In the case of unicellular organisms such as bacteria and yeast, this process is remarkably simple and essentially only requires the inoculation of the appropriate medium. However, in the case of cell cultures from multi-cellular organisms, cell cloning is an arduous task as these cells will not readily grow in standard media.

A useful tissue culture technique used to clone distinct lineages of cell lines involves the use of cloning rings (cylinders).[9] In this technique a single-cell suspension of cells that have been exposed to a mutagenic agent or drug used to drive selection is plated at high dilution to create isolated colonies, each arising from a single and potentially clonal distinct cell. At an early growth stage when colonies consist of only a few cells, sterile polystyrene rings (cloning rings), which have been dipped in grease, are placed over an individual colony and a small amount of trypsin is added. Cloned cells are collected from inside the ring and transferred to a new vessel for further growth.

Somatic-cell nuclear transfer, known as SCNT, can also be used to create embryos for research or therapeutic purposes. The most likely purpose for this is to produce embryos for use in stem cell research. This process is also called "research cloning" or "therapeutic cloning." The goal is not to create cloned human beings (called "reproductive cloning"), but rather to harvest stem cells that can be used to study human development and to potentially treat disease. While a clonal human blastocyst has been created, stem cell lines are yet to be isolated from a clonal source.[10]

Therapeutic cloning is achieved by creating embryonic stem cells in the hopes of treating diseases such as diabetes and Alzheimer's. The process begins by removing the nucleus (containing the DNA) from an egg cell and inserting a nucleus from the adult cell to be cloned.[11] In the case of someone with Alzheimer's disease, the nucleus from a skin cell of that patient is placed into an empty egg. The reprogrammed cell begins to develop into an embryo because the egg reacts with the transferred nucleus. The embryo will become genetically identical to the patient.[11] The embryo will then form a blastocyst which has the potential to form/become any cell in the body.[12]

The reason why SCNT is used for cloning is because somatic cells can be easily acquired and cultured in the lab. This process can either add or delete specific genomes of farm animals. A key point to remember is that cloning is achieved when the oocyte maintains its normal functions and instead of using sperm and egg genomes to replicate, the oocyte is inserted into the donors somatic cell nucleus.[13] The oocyte will react on the somatic cell nucleus, the same way it would on sperm cells.[13]

The process of cloning a particular farm animal using SCNT is relatively the same for all animals. The first step is to collect the somatic cells from the animal that will be cloned. The somatic cells could be used immediately or stored in the laboratory for later use.[13] The hardest part of SCNT is removing maternal DNA from an oocyte at metaphase II. Once this has been done, the somatic nucleus can be inserted into an egg cytoplasm.[13] This creates a one-cell embryo. The grouped somatic cell and egg cytoplasm are then introduced to an electrical current.[13] This energy will hopefully allow the cloned embryo to begin development. The successfully developed embryos are then placed in surrogate recipients, such as a cow or sheep in the case of farm animals.[13]

SCNT is seen as a good method for producing agriculture animals for food consumption. It successfully cloned sheep, cattle, goats, and pigs. Another benefit is SCNT is seen as a solution to clone endangered species that are on the verge of going extinct.[13] However, stresses placed on both the egg cell and the introduced nucleus can be enormous, which led to a high loss in resulting cells in early research. For example, the cloned sheep Dolly was born after 277 eggs were used for SCNT, which created 29 viable embryos. Only three of these embryos survived until birth, and only one survived to adulthood.[14] As the procedure could not be automated, and had to be performed manually under a microscope, SCNT was very resource intensive. The biochemistry involved in reprogramming the differentiated somatic cell nucleus and activating the recipient egg was also far from being well-understood. However, by 2014 researchers were reporting cloning success rates of seven to eight out of ten[15] and in 2016, a Korean Company Sooam Biotech was reported to be producing 500 cloned embryos per day.[16]

In SCNT, not all of the donor cell's genetic information is transferred, as the donor cell's mitochondria that contain their own mitochondrial DNA are left behind. The resulting hybrid cells retain those mitochondrial structures which originally belonged to the egg. As a consequence, clones such as Dolly that are born from SCNT are not perfect copies of the donor of the nucleus.

Organism cloning (also called reproductive cloning) refers to the procedure of creating a new multicellular organism, genetically identical to another. In essence this form of cloning is an asexual method of reproduction, where fertilization or inter-gamete contact does not take place. Asexual reproduction is a naturally occurring phenomenon in many species, including most plants (see vegetative reproduction) and some insects. Scientists have made some major achievements with cloning, including the asexual reproduction of sheep and cows. There is a lot of ethical debate over whether or not cloning should be used. However, cloning, or asexual propagation,[17] has been common practice in the horticultural world for hundreds of years.

The term clone is used in horticulture to refer to descendants of a single plant which were produced by vegetative reproduction or apomixis. Many horticultural plant cultivars are clones, having been derived from a single individual, multiplied by some process other than sexual reproduction.[18] As an example, some European cultivars of grapes represent clones that have been propagated for over two millennia. Other examples are potato and banana.[19]Grafting can be regarded as cloning, since all the shoots and branches coming from the graft are genetically a clone of a single individual, but this particular kind of cloning has not come under ethical scrutiny and is generally treated as an entirely different kind of operation.

Many trees, shrubs, vines, ferns and other herbaceous perennials form clonal colonies naturally. Parts of an individual plant may become detached by fragmentation and grow on to become separate clonal individuals. A common example is in the vegetative reproduction of moss and liverwort gametophyte clones by means of gemmae. Some vascular plants e.g. dandelion and certain viviparous grasses also form seeds asexually, termed apomixis, resulting in clonal populations of genetically identical individuals.

Clonal derivation exists in nature in some animal species and is referred to as parthenogenesis (reproduction of an organism by itself without a mate). This is an asexual form of reproduction that is only found in females of some insects, crustaceans, nematodes,[20] fish (for example the hammerhead shark[21]), the Komodo dragon[21] and lizards. The growth and development occurs without fertilization by a male. In plants, parthenogenesis means the development of an embryo from an unfertilized egg cell, and is a component process of apomixis. In species that use the XY sex-determination system, the offspring will always be female. An example is the little fire ant (Wasmannia auropunctata), which is native to Central and South America but has spread throughout many tropical environments.

Artificial cloning of organisms may also be called reproductive cloning.

Hans Spemann, a German embryologist was awarded a Nobel Prize in Physiology or Medicine in 1935 for his discovery of the effect now known as embryonic induction, exercised by various parts of the embryo, that directs the development of groups of cells into particular tissues and organs. In 1928 he and his student, Hilde Mangold, were the first to perform somatic-cell nuclear transfer using amphibian embryos one of the first moves towards cloning.[22]

Reproductive cloning generally uses "somatic cell nuclear transfer" (SCNT) to create animals that are genetically identical. This process entails the transfer of a nucleus from a donor adult cell (somatic cell) to an egg from which the nucleus has been removed, or to a cell from a blastocyst from which the nucleus has been removed.[23] If the egg begins to divide normally it is transferred into the uterus of the surrogate mother. Such clones are not strictly identical since the somatic cells may contain mutations in their nuclear DNA. Additionally, the mitochondria in the cytoplasm also contains DNA and during SCNT this mitochondrial DNA is wholly from the cytoplasmic donor's egg, thus the mitochondrial genome is not the same as that of the nucleus donor cell from which it was produced. This may have important implications for cross-species nuclear transfer in which nuclear-mitochondrial incompatibilities may lead to death.

Artificial embryo splitting or embryo twinning, a technique that creates monozygotic twins from a single embryo, is not considered in the same fashion as other methods of cloning. During that procedure, an donor embryo is split in two distinct embryos, that can then be transferred via embryo transfer. It is optimally performed at the 6- to 8-cell stage, where it can be used as an expansion of IVF to increase the number of available embryos.[24] If both embryos are successful, it gives rise to monozygotic (identical) twins.

Dolly, a Finn-Dorset ewe, was the first mammal to have been successfully cloned from an adult somatic cell. Dolly was formed by taking a cell from the udder of her 6-year old biological mother.[25] Dolly's embryo was created by taking the cell and inserting it into a sheep ovum. It took 434 attempts before an embryo was successful.[26] The embryo was then placed inside a female sheep that went through a normal pregnancy.[27] She was cloned at the Roslin Institute in Scotland by British scientists Sir Ian Wilmut and Keith Campbell and lived there from her birth in 1996 until her death in 2003 when she was six. She was born on 5 July 1996 but not announced to the world until 22 February 1997.[28] Her stuffed remains were placed at Edinburgh's Royal Museum, part of the National Museums of Scotland.[29]

Dolly was publicly significant because the effort showed that genetic material from a specific adult cell, programmed to express only a distinct subset of its genes, can be reprogrammed to grow an entirely new organism. Before this demonstration, it had been shown by John Gurdon that nuclei from differentiated cells could give rise to an entire organism after transplantation into an enucleated egg.[30] However, this concept was not yet demonstrated in a mammalian system.

The first mammalian cloning (resulting in Dolly the sheep) had a success rate of 29 embryos per 277 fertilized eggs, which produced three lambs at birth, one of which lived. In a bovine experiment involving 70 cloned calves, one-third of the calves died young. The first successfully cloned horse, Prometea, took 814 attempts. Notably, although the first[clarification needed] clones were frogs, no adult cloned frog has yet been produced from a somatic adult nucleus donor cell.

There were early claims that Dolly the sheep had pathologies resembling accelerated aging. Scientists speculated that Dolly's death in 2003 was related to the shortening of telomeres, DNA-protein complexes that protect the end of linear chromosomes. However, other researchers, including Ian Wilmut who led the team that successfully cloned Dolly, argue that Dolly's early death due to respiratory infection was unrelated to deficiencies with the cloning process. This idea that the nuclei have not irreversibly aged was shown in 2013 to be true for mice.[31]

Dolly was named after performer Dolly Parton because the cells cloned to make her were from a mammary gland cell, and Parton is known for her ample cleavage.[32]

The modern cloning techniques involving nuclear transfer have been successfully performed on several species. Notable experiments include:

Human cloning is the creation of a genetically identical copy of a human. The term is generally used to refer to artificial human cloning, which is the reproduction of human cells and tissues. It does not refer to the natural conception and delivery of identical twins. The possibility of human cloning has raised controversies. These ethical concerns have prompted several nations to pass legislature regarding human cloning and its legality.

Two commonly discussed types of theoretical human cloning are therapeutic cloning and reproductive cloning. Therapeutic cloning would involve cloning cells from a human for use in medicine and transplants, and is an active area of research, but is not in medical practice anywhere in the world, as of 2014. Two common methods of therapeutic cloning that are being researched are somatic-cell nuclear transfer and, more recently, pluripotent stem cell induction. Reproductive cloning would involve making an entire cloned human, instead of just specific cells or tissues.[57]

There are a variety of ethical positions regarding the possibilities of cloning, especially human cloning. While many of these views are religious in origin, the questions raised by cloning are faced by secular perspectives as well. Perspectives on human cloning are theoretical, as human therapeutic and reproductive cloning are not commercially used; animals are currently cloned in laboratories and in livestock production.

Advocates support development of therapeutic cloning in order to generate tissues and whole organs to treat patients who otherwise cannot obtain transplants,[58] to avoid the need for immunosuppressive drugs,[57] and to stave off the effects of aging.[59] Advocates for reproductive cloning believe that parents who cannot otherwise procreate should have access to the technology.[60]

Opponents of cloning have concerns that technology is not yet developed enough to be safe[61] and that it could be prone to abuse (leading to the generation of humans from whom organs and tissues would be harvested),[62][63] as well as concerns about how cloned individuals could integrate with families and with society at large.[64][65]

Religious groups are divided, with some opposing the technology as usurping "God's place" and, to the extent embryos are used, destroying a human life; others support therapeutic cloning's potential life-saving benefits.[66][67]

Cloning of animals is opposed by animal-groups due to the number of cloned animals that suffer from malformations before they die,[68][69] and while food from cloned animals has been approved by the US FDA,[70][71] its use is opposed by groups concerned about food safety.[72][73][74]

Cloning, or more precisely, the reconstruction of functional DNA from extinct species has, for decades, been a dream. Possible implications of this were dramatized in the 1984 novel Carnosaur and the 1990 novel Jurassic Park.[75][76] The best current cloning techniques have an average success rate of 9.4 percent[77] (and as high as 25 percent[31]) when working with familiar species such as mice,[note 1] while cloning wild animals is usually less than 1 percent successful.[80] Several tissue banks have come into existence, including the "Frozen Zoo" at the San Diego Zoo, to store frozen tissue from the world's rarest and most endangered species.[75][81][82]

In 2001, a cow named Bessie gave birth to a cloned Asian gaur, an endangered species, but the calf died after two days. In 2003, a banteng was successfully cloned, followed by three African wildcats from a thawed frozen embryo. These successes provided hope that similar techniques (using surrogate mothers of another species) might be used to clone extinct species. Anticipating this possibility, tissue samples from the last bucardo (Pyrenean ibex) were frozen in liquid nitrogen immediately after it died in 2000. Researchers are also considering cloning endangered species such as the giant panda and cheetah.

In 2002, geneticists at the Australian Museum announced that they had replicated DNA of the thylacine (Tasmanian tiger), at the time extinct for about 65 years, using polymerase chain reaction.[83] However, on 15 February 2005 the museum announced that it was stopping the project after tests showed the specimens' DNA had been too badly degraded by the (ethanol) preservative. On 15 May 2005 it was announced that the thylacine project would be revived, with new participation from researchers in New South Wales and Victoria.

In January 2009, for the first time, an extinct animal, the Pyrenean ibex mentioned above was cloned, at the Centre of Food Technology and Research of Aragon, using the preserved frozen cell nucleus of the skin samples from 2001 and domestic goat egg-cells. The ibex died shortly after birth due to physical defects in its lungs.[84]

One of the most anticipated targets for cloning was once the woolly mammoth, but attempts to extract DNA from frozen mammoths have been unsuccessful, though a joint Russo-Japanese team is currently working toward this goal. In January 2011, it was reported by Yomiuri Shimbun that a team of scientists headed by Akira Iritani of Kyoto University had built upon research by Dr. Wakayama, saying that they will extract DNA from a mammoth carcass that had been preserved in a Russian laboratory and insert it into the egg cells of an African elephant in hopes of producing a mammoth embryo. The researchers said they hoped to produce a baby mammoth within six years.[85][86] It was noted, however that the result, if possible, would be an elephant-mammoth hybrid rather than a true mammoth.[87] Another problem is the survival of the reconstructed mammoth: ruminants rely on a symbiosis with specific microbiota in their stomachs for digestion.[87]

Scientists at the University of Newcastle and University of New South Wales announced in March 2013 that the very recently extinct gastric-brooding frog would be the subject of a cloning attempt to resurrect the species.[88]

Many such "de-extinction" projects are described in the Long Now Foundation's Revive and Restore Project.[89]

After an eight-year project involving the use of a pioneering cloning technique, Japanese researchers created 25 generations of healthy cloned mice with normal lifespans, demonstrating that clones are not intrinsically shorter-lived than naturally born animals.[31][90]

In a detailed study released in 2016 and less detailed studies by others suggest that once cloned animals get past the first month or two of life they are generally healthy. However, early pregnancy loss and neonatal losses are still greater with cloning than natural conception or assisted reproduction (IVF). Current research endeavors are attempting to overcome this problem.[32]

In an article in the 8 November 1993 article of Time, cloning was portrayed in a negative way, modifying Michelangelo's Creation of Adam to depict Adam with five identical hands. Newsweek's 10 March 1997 issue also critiqued the ethics of human cloning, and included a graphic depicting identical babies in beakers.

Cloning is a recurring theme in a wide variety of contemporary science fiction, ranging from action films such as Jurassic Park (1993), The 6th Day (2000), Resident Evil (2002), Star Wars (2002) and The Island (2005), to comedies such as Woody Allen's 1973 film Sleeper.[91]

Science fiction has used cloning, most commonly and specifically human cloning, due to the fact that it brings up controversial questions of identity.[92][93]A Number is a 2002 play by English playwright Caryl Churchill which addresses the subject of human cloning and identity, especially nature and nurture. The story, set in the near future, is structured around the conflict between a father (Salter) and his sons (Bernard 1, Bernard 2, and Michael Black) two of whom are clones of the first one. A Number was adapted by Caryl Churchill for television, in a co-production between the BBC and HBO Films.[94]

A recurring sub-theme of cloning fiction is the use of clones as a supply of organs for transplantation. The 2005 Kazuo Ishiguro novel Never Let Me Go and the 2010 film adaption[95] are set in an alternate history in which cloned humans are created for the sole purpose of providing organ donations to naturally born humans, despite the fact that they are fully sentient and self-aware. The 2005 film The Island[96] revolves around a similar plot, with the exception that the clones are unaware of the reason for their existence.

The use of human cloning for military purposes has also been explored in several works. Star Wars portrays human cloning in Clone Wars.[97]

The exploitation of human clones for dangerous and undesirable work was examined in the 2009 British science fiction film Moon.[98] In the futuristic novel Cloud Atlas and subsequent film, one of the story lines focuses on a genetically-engineered fabricant clone named Sonmi~451 who is one of millions raised in an artificial "wombtank," destined to serve from birth. She is one of thousands of clones created for manual and emotional labor; Sonmi herself works as a server in a restaurant. She later discovers that the sole source of food for clones, called 'Soap', is manufactured from the clones themselves.[99]

Cloning has been used in fiction as a way of recreating historical figures. In the 1976 Ira Levin novel The Boys from Brazil and its 1978 film adaptation, Josef Mengele uses cloning to create copies of Adolf Hitler.[100]

In 2012, a Japanese television show named "Bunshin" was created. The story's main character, Mariko, is a woman studying child welfare in Hokkaido. She grew up always doubtful about the love from her mother, who looked nothing like her and who died nine years before. One day, she finds some of her mother's belongings at a relative's house, and heads to Tokyo to seek out the truth behind her birth. She later discovered that she was a clone.[101]

In the 2013 television show Orphan Black, cloning is used as a scientific study on the behavioral adaptation of the clones.[102] In a similar vein, the book The Double by Nobel Prize winner Jos Saramago explores the emotional experience of a man who discovers that he is a clone.[103]

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Cloning - Wikipedia

Characterization of Regenerative Phenotype of Unrestricted …

Somatic Stem Cells | Posted by admin
Dec 01 2016

Stem cell transplantation is a promising therapeutic strategy to enhance axonal regeneration after spinal cord injury. Unrestricted somatic stem cells (USSC) isolated from human umbilical cord blood is an attractive stem cell population available at GMP grade without any ethical concerns. It has been shown that USSC transplantation into acute injured rat spinal cords leads to axonal regrowth and significant locomotor recovery, yet lacking cell replacement. Instead, USSC secrete trophic factors enhancing neurite growth of primary cortical neurons in vitro. Here, we applied a functional secretome approach characterizing proteins secreted by USSC for the first time and validated candidate neurite growth promoting factors using primary cortical neurons in vitro. By mass spectrometric analysis and exhaustive bioinformatic interrogation we identified 1156 proteins representing the secretome of USSC. Using Gene Ontology we revealed that USSC secretome contains proteins involved in a number of relevant biological processes of nerve regeneration such as cell adhesion, cell motion, blood vessel formation, cytoskeleton organization and extracellular matrix organization. We found for instance that 31 well-known neurite growth promoting factors like, e.g. neuronal growth regulator 1, NDNF, SPARC, and PEDF span the whole abundance range of USSC secretome. By the means of primary cortical neurons in vitro assays we verified SPARC and PEDF as significantly involved in USSC mediated neurite growth and therewith underline their role in improved locomotor recovery after transplantation. From our data we are convinced that USSC are a valuable tool in regenerative medicine as USSC's secretome contains a comprehensive network of trophic factors supporting nerve regeneration not only by a single process but also maintained its regenerative phenotype by a multitude of relevant biological processes.

2015 by The American Society for Biochemistry and Molecular Biology, Inc.

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Characterization of Regenerative Phenotype of Unrestricted ...