Stem Cell Clinic

Cloning/Embryonic Stem Cells – National Human Genome …

Cloning/Embryonic Stem Cells

The term cloning is used by scientists to describe many different processes that involve making duplicates of biological material. In most cases, isolated genes or cells are duplicated for scientific study, and no new animal results. The experiment that led to the cloning of Dolly the sheep in 1997 was different: It used a cloning technique called somatic cell nuclear transfer and resulted in an animal that was a genetic twin -- although delayed in time -- of an adult sheep. This technique can also be used to produce an embryo from which cells called embryonic stem (ES) cells could be extracted to use in research into potential therapies for a wide variety of diseases.

Thus, in the past five years, much of the scientific and ethical debate about somatic cell nuclear transfer has focused on its two potential applications: 1) for reproductive purposes, i.e., to produce a child, or 2) for producing a source of ES cells for research.

The technique of transferring a nucleus from a somatic cell into an egg that produced Dolly was an extension of experiments that had been ongoing for over 40 years. In the simplest terms, the technique used to produce Dolly the sheep - somatic cell nuclear transplantation cloning - involves removing the nucleus of an egg and replacing it with the diploid nucleus of a somatic cell. Unlike sexual reproduction, during which a new organism is formed when the genetic material of the egg and sperm fuse, in nuclear transplantation cloning there is a single genetic "parent." This technique also differs from previous cloning techniques because it does not involve an existing embryo. Dolly is different because she is not genetically unique; when born she was genetically identical to an existing six-year-old ewe. Although the birth of Dolly was lauded as a success, in fact, the procedure has not been perfected and it is not yet clear whether Dolly will remain healthy or whether she is already experiencing subtle problems that might lead to serious diseases. Thus, the prospect of applying this technique in humans is troubling for scientific and safety reasons in addition to a variety of ethical reasons related to our ideas about the natural ordering of family and successive generations.

Several important concerns remain about the science and safety of nuclear transfer cloning using adult cells as the source of nuclei. To date, five mammalian species -- sheep, cattle, pigs, goats, and mice -- have been used extensively in reproductive cloning studies. Data from these experiments illustrate the problems involved. Typically, very few cloning attempts are successful. Many cloned animals die in utero, even at late stages or soon after birth, and those that survive frequently exhibit severe birth defects. In addition, female animals carrying cloned fetuses may face serious risks, including death from cloning-related complications.

An additional concern focuses on whether cellular aging will affect the ability of somatic cell nuclei to program normal development. As somatic cells divide they progressively age, and there is normally a defined number of cell divisions that can occur before senescence. Thus, the health effects for the resulting liveborn, having been created with an "aged" nucleus, are unknown. Recently it was reported that Dolly has arthritis, although it is not yet clear whether the five-and-a-half-year-old sheep is suffering from the condition as a result of the cloning process. And, scientists in Tokyo have shown that cloned mice die significantly earlier than those that are naturally conceived, raising an additional concern that the mutations that accumulate in somatic cells might affect nuclear transfer efficiency and lead to cancer and other diseases in offspring. Researchers working with clones of a Holstein cow say genetic programming errors may explain why so many cloned animals die, either as fetuses or newborns.

The announcement of Dolly sparked widespread speculation about a human child being created using somatic cell nuclear transfer. Much of the perceived fear that greeted this announcement centered on the misperception that a child or many children could be produced who would be identical to an already existing person. This fear is based on the idea of "genetic determinism" -- that genes alone determine all aspects of an individual -- and reflects the belief that a person's genes bear a simple relationship to the physical and psychological traits that compose that individual. Although genes play an essential role in the formation of physical and behavioral characteristics, each individual is, in fact, the result of a complex interaction between his or her genes and the environment within which he or she develops. Nonetheless, many of the concerns about cloning have focused on issues related to "playing God," interfering with the natural order of life, and somehow robbing a future individual of the right to a unique identity.

Several groups have concluded that reproductive cloning of human beings creates ethical and scientific risks that society should not tolerate. In 1997, the National Bioethics Advisory Commission recommended that it was morally unacceptable to attempt to create a child using somatic cell nuclear transfer cloning and suggested that a moratorium be imposed until safety of this technique could be assessed. The commission also cautioned against preempting the use of cloning technology for purposes unrelated to producing a liveborn child.

Similarly, in 2001 the National Academy of Sciences issued a report stating that the United States should ban human reproductive cloning aimed at creating a child because experience with reproductive cloning in animals suggests that the process would be dangerous for the woman, the fetus, and the newborn, and would likely fail. The report recommended that the proposed ban on human cloning should be reviewed within five years, but that it should be reconsidered "only if a new scientific review indicates that the procedures are likely to be safe and effective, and if a broad national dialogue on societal, religious and ethical issues suggests that reconsideration is warranted." The panel concluded that the scientific and medical considerations that justify a ban on human reproductive cloning at this time do not apply to nuclear transplantation to produce stem cells. Several other scientific and medical groups also have stated their opposition to the use of cloning for the purpose of producing a child.

The cloning debate was reopened with a new twist late in 1998, when two scientific reports were published regarding the successful isolation of human stem cells. Stem cells are unique and essential cells found in animals that are capable of continually reproducing themselves and renewing tissue throughout an individual organism's life. ES cells are the most versatile of all stem cells because they are less differentiated, or committed, to a particular function than adult stem cells. These cells have offered hope of new cures to debilitating and even fatal illness. Recent studies in mice and other animals have shown that ES cells can reduce symptoms of Parkinson's disease in mouse models, and work in other animal models and disease areas seems promising.

In the 1998 reports, ES cells were derived from in vitro embryos six to seven days old destined to be discarded by couples undergoing infertility treatments, and embryonic germ (EG) cells were obtained from cadaveric fetal tissue following elective abortion. A third report, appearing in the New York Times, claimed that a Massachusetts biotechnology company had fused a human cell with an enucleated cow egg, creating a hybrid clone that failed to progress beyond an early stage of development. This announcement served as a reminder that ES cells also could be derived from embryos created through somatic cell nuclear transfer, or cloning. In fact, several scientists believed that deriving ES cells in this manner is the most promising approach to developing treatments because the condition of in vitro fertilization (IVF) embryos stored over time is questionable and this type of cloning could overcome graft-host responses if resulting therapies were developed from the recipient's own DNA.

For those who believe that the embryo has the moral status of a person from the moment of conception, research or any other activity that would destroy it is wrong. For those who believe the human embryo deserves some measure of respect, but disagree that the respect due should equal that given to a fully formed human, it could be considered immoral not to use embryos that would otherwise be destroyed to develop potential cures for disease affecting millions of people. An additional concern related to public policy is whether federal funds should be used for research that some Americans find unethical.

Since 1996, Congress has prohibited researchers from using federal funds for human embryo research. In 1999, DHHS announced that it intended to fund research on human ES cells derived from embryos remaining after infertility treatments. This decision was based on an interpretation "that human embryonic stem cells are not a human embryo within the statutory definition" because "the cells do not have the capacity to develop into a human being even if transferred to the uterus, thus their destruction in the course of research would not constitute the destruction of an embryo." DHHS did not intend to fund research using stem cells derived from embryos created through cloning, although such efforts would be legal in the private sector.

In July 2001, the House of Representatives voted 265 to 162 to make any human cloning a criminal offense, including cloning to create an embryo for derivation of stem cells rather than to produce a child. In August 2002, President Bush, contending with a DHHS decision made during the Clinton administration, stated in a prime-time television address that federal support would be provided for research using a limited number of stem cell colonies already in existence (derived from leftover IVF embryos). Current bills before Congress would ban all forms of cloning outright, prohibit cloning for reproductive purposes, and impose a moratorium on cloning to derive stem cells for research, or prohibit cloning for reproductive purposes while allowing cloning for therapeutic purposes to go forward. As of late June, the Senate has taken no action. President Bush's Bioethics Council is expected to recommend the prohibition of reproductive cloning and a moratorium on therapeutic cloning later this summer.

Prepared by Kathi E. Hanna, M.S., Ph.D., Science and Health Policy Consultant

Last Reviewed: April 2006

Read the original here:
Cloning/Embryonic Stem Cells - National Human Genome ...

In a first, scientists rid human embryos of a potentially fatal gene mutation by editing their DNA – Los Angeles Times

Using a powerful gene-editing technique, scientists have rid human embryos of a mutation responsible for an inherited form of heart disease thats often deadly to healthy young athletes and adults in their prime.

The experiment marks the first time that scientists have altered the human genome to erase a disease-causing mutation not only from the DNA of the primary subject but from the genes of his or her progeny as well.

The controversial procedure, known as germ-line editing, was conducted at Oregon Health and Science University in Portland using human embryos expressly created for the purpose. It was reported Wednesday in the journal Nature.

Scientists ultimate goal is to fix gene mutations that lead to debilitating or fatal diseases, and to prevent the propagation of those mutations to future generations. Study leader Shoukhrat Mitalipov, a biologist at OHSU, said the new findings might correct genetic variants that can cause breast and ovarian cancer, cystic fibrosis and muscular dystrophy in those who inherit them.

But others fret that the technique may be used for less noble purposes, such as creating designer babies with desired traits like green eyes, an athletic build or an aptitude for mathematics.

In the United States, the Food and Drug Administration currently forbids any use of germ-line editing outside of a research setting.

But recent history has shown that people who want access to such techniques can find people willing to perform them in venues where theyre able to do so, said Jeffrey Kahn, who directs Johns Hopkins Universitys Berman Institute of Bioethics.

It will happen whether we discuss it or not, and we need to talk about these things before they happen, said Kahn. Thats now.

The new research comes less than six months after the National Academies of Science, Engineering and Medicine recommended that scientists limit their trials of human germ-line editing to diseases that could not be treated with reasonable alternatives at least for the time being.

In a bid to make the experiment relevant to the real-life problems faced by parents who carry disease-causing mutations, the researchers focused on a gene variant that causes inherited hypertrophic cardiomyopathy.

In this condition, a parent who carries one normal and one mutated copy of the MYBPC3 gene has a 50-50 chance of passing the faulty copy on to his or her offspring. If the child inherits the mutation, his or her heart muscle is likely to grow prematurely weak and stiff, causing heart failure and often early death.

In diseases in which one parent carries a gene like this, a couple will often seek the assistance of fertility doctors to minimize the risk of passing the mutation on to a child. A womans eggs and mans sperm meet in a lab using in vitro fertilization. Then specialists inspect the resulting embryos, cull the ones that have inherited an unwanted mutation, and transfer unaffected embryos into a womans uterus to be carried to term.

In the new research, researchers set out to test whether germ-line gene editing could make the process of choosing healthy embryos more effective and efficient by creating more of them.

It could. The targeted correction of a disease-causing gene carried by a single parent can potentially rescue a substantial portion of mutant human embryos, thus increasing the number of embryos available for transfer, the study authors reported.

The fix was made possible by a system known as CRISPR-Cas9, which has been sweeping through biology labs because it greatly simplifies the gene-editing process. It uses a small piece of RNA and an enzyme to snip out unwanted DNA and, if desired, replace it with something better.

If the process is found to be safe for use in fertility clinics, it could potentially decrease the number of cycles needed for people trying to have children free of genetic disease, said Dr. Paula Amato, a coauthor and professor of obstetrics and gynecology at Oregon Health and Science University.

The team encountered several scientific surprises along the way. Long-feared effects of germ-line editing, including collateral damage to off-target genetic sequences, scarcely materialized. And mosaicism, a phenomenon in which edited DNA appears in some but not all cells, was found to be minimal.

Mitalipov called these exciting and surprising moments. But he cautioned that there is room to improve the techniques for producing mutation-free embryos. Clinical trials would have to wait until the DNA editing showed a near-perfect level of efficiency and accuracy, he said, and could be limited by state and federal regulations.

There is still a long road ahead, said Mitalipov, who heads the Center for Embryonic Cell and Gene Therapy at OHSU.

Oregon Health & Science University

Human embryos developing into blastocysts after being injected with a gene-correcting enzyme and sperm carrying a mutation for a potentially fatal disease of the heart muscle.

Human embryos developing into blastocysts after being injected with a gene-correcting enzyme and sperm carrying a mutation for a potentially fatal disease of the heart muscle. (Oregon Health & Science University)

Oregon Health & Science University

Individual blastomeres within the early embryos two days after the co-injection. Each new cell in the developing embryos was uniformly free of the disease-causing mutation.

Individual blastomeres within the early embryos two days after the co-injection. Each new cell in the developing embryos was uniformly free of the disease-causing mutation. (Oregon Health & Science University)

Biologists, fertility doctors and ethicists have long anticipated that scientists would one day manipulate the DNA of human embryos. Now that the milestone has been reached, it drew a mix of praise and concern from experts in genetic medicine.

Dr. Richard O. Hynes, who co-chaired the National Academies report issued in February, called the new study very good science that advances the understanding of genetic repair on many fronts. Hynes, who was not involved with the research effort, said he was pleasantly surprised by the Oregon-based teams clever modifications and their outcomes.

Its likely to become feasible, technically not tomorrow, not next year, but in some foreseeable time. Less than a decade, Id say, said Hynes, a biologist and cancer researcher at MIT and the Howard Hughes Medical Institute.

UC Berkeley molecular and cell biologist Jennifer Doudna, one of pioneers of the CRISPR-Cas9 gene-editing system, said the new research highlights a prospective use of gene editing for one inherited disease and offers some insights into the process. But she questioned how broadly the experiments results would apply to other inherited diseases.

Doudna also said she does not believe using germ-line editing to improve efficiency at fertility clinics meets the criteria laid out by the National Academies of Sciences, which urged that the technology be explored only in cases in which its needed essentially as a last resort.

Already, 50% of embryos would be normal, she said. Why not just implant those?

Doudna said she feared that the new findings will encourage people to proceed down this road before the scientific and ethical implications of germ-line editing have been fully considered.

A large group of experts concluded that clinical use should not proceed until and unless theres broad societal consensus, and that just hasnt happened, she said. This study underscores the urgency of having those debates. Because its coming.

Kristyna Wentz-Graff/Oregon Health & Science University

Study leader Shoukhrat Mitalipov with coauthors Hong Ma, left, and Nuria Marti-Gutierrez.

Study leader Shoukhrat Mitalipov with coauthors Hong Ma, left, and Nuria Marti-Gutierrez. (Kristyna Wentz-Graff/Oregon Health & Science University)

The study authors a multinational team of geneticists, cardiologists, fertility experts and embryologists from OHSU, the Salk Institute in La Jolla, and labs in South Korea and China tested a number of innovations in an effort to improve the safety, efficiency and fidelity of gene editing. And most yielded promising results.

After retrieving eggs from 12 healthy female volunteers, the researchers simultaneously performed two steps that had never been combined in a lab: fertilizing the eggs with sperm and introducing the CRISPR-Cas9 repair machinery.

The resulting embryos took up the gene-editing program so efficiently and uniformly that, after five days of incubation, 72.4% of the 58 embryos tested were free of the MYBPC3 mutation. By comparison, when there was no attempt at gene editing, just 47.4% of embryos were free of the mutation responsible for the deadly heart condition.

The researchers believe their method prompted the embryos to rely on the healthy maternal copy of the gene as a model for fixing the MYBPC3 mutation, and not a repair template that used DNA from the sperm donors normal version of the gene. Only one of the 42 embryos used the introduced template for repair. The scientists contrasted this process to stem cells, which do use repair templates.

The embryos cells divided normally as they matured to the blastocyst stage, the point at which they would usually be ready for transfer to a womans uterus. After extensive testing, the embryos were used to make embryonic stem-cell lines, which are stored in liquid nitrogen and can be used in future research.

Researchers also noted that genetic mosaicism a concern raised by earlier experiments in gene-editing was virtually absent from 41 of the 42 embryos that were free of the disease-causing mutation.

MITs Hynes said such findings offer important insights into how human embryos grow, develop and respond to anomalies, and will help families facing infertility and inherited illnesses.

Human embryogenesis is clearly different from that of a mouse, which we know a lot about, Hynes said. That needs to be studied in human embryos, and theres no other way to do it.

At the same time, he downplayed fears that embryologists would soon tinker with such attributes as looks, personality traits and intelligence in human children.

Were not looking at designed babies around the corner not for a long time, he said.

melissa.healy@latimes.com

@LATMelissaHealy

MORE IN SCIENCE

The DNA of ancient Canaanites lives on in modern-day Lebanese, genetic analysis shows

You can predict how many blacks are killed by police by measuring the racism of whites, research finds

Is it Alzheimers or another dementia form? Why doctors need to distinguish and how they might do so

UPDATES:

3:50 p.m.: This story has been updated with comments from Jeffrey Kahn of Johns Hopkins Universitys Berman Institute of Bioethics.

This story was originally published at 10 a.m.

Read more here:
In a first, scientists rid human embryos of a potentially fatal gene mutation by editing their DNA - Los Angeles Times

Breakthrough: Doctors can now ‘edit’ genes in human embryos – Health24

04 August 2017 Breakthrough: Doctors can now edit genes in human embryos A new technique can potentially be used to prevent transmission of genetic disease to future generations.

In a first-ever experiment, geneticists have successfully modified a human embryo to remove a mutation that causes a life-threatening heart condition.

This is the first study to demonstrate that a gene-editing technique can be used in human embryos to convert mutant genes back to their normal version, the researchers said.

This new procedure tackled a genetic mutation in human embryos that causes hypertrophic cardiomyopathy, an inherited condition in which the heart muscle becomes abnormally thick.

The mutation was successfully repaired in 72% of 18 embryos that were created in a lab using sperm from a male donor who carries the hereditary heart condition, said team member Dr Paula Amato. She is an adjunct associate professor of obstetrics and gynaecology at Oregon Health & Science University (OHSU) in Portland.

Unlike other parts of the world in which cardiomyopathy is rare, heart muscle disease is endemic in Africa.

Impact on future generations

The procedure also might work in other genetic diseases caused when a person has one good copy and one mutated copy of a gene, Amato said. These include cystic fibrosis and cancers caused by mutated BRCA genes.

"This embryo gene correction method, if proven safe, can potentially be used to prevent transmission of genetic disease to future generations," Amato said.

But while the procedure is considered to be the first of its kind, human trials are not currently allowed in the United States.

A serious heart condition

Hereditary hypertrophic cardiomyopathy occurs in about one out of every 500 adults, and is passed along when a person winds up with one good copy and one mutated copy of a gene called MYBPC3, the researchers said.

There's a 50% chance that the children of a parent with the disease will inherit the genetic mutation for the disease, according to a Mayo Clinic estimate.

People with hypertrophic cardiomyopathy are at increased risk of heart failure and sudden heart death. The condition is the most common cause of sudden death in otherwise healthy young athletes, researchers said in background notes.

How the 'editing' is done

To repair the problem, the research team "broke" the mutated version of the MYPBC3 gene inside human embryos, using technology that allows scientists to snip a specific target sequence on a mutant gene.

Scientists discovered that when this occurs, a DNA repair process employed within human embryos activates to fix the broken gene, using the normal copy of the gene as a template.

The result: an embryo with two healthy copies of the gene that, if implanted in a woman and allowed to gestate, should result in a baby free from risk of hereditary cardiomyopathy. Further, any children descended from that baby should also be free from this genetic risk.

The researchers found that when they performed this procedure, all the cells in corrected embryos wound up containing two normal copies of the gene, Amato said. The new report was published in the journalNature.

The next step

Researchers will next focus on testing the safety and improving the efficiency of the CRISPR-Cas9 process, possibly by using other genetic tools in combination with it, Mitalipov said. After that, they could proceed to human trials, in which the corrected embryos would be implanted with the goal of establishing pregnancy.

In the United States, the US Food and Drug Administration is prohibited from considering clinical trials related to germline genetic modification, Amato said. In addition, the US National Institutes of Health are not allowed to use federal funds to promote embryo research. It is possible that human trials could occur in another country with laws allowing such procedures, Mitalipov said.

In the area of stem cell research, South Africa allows the derivation of human embryonic stem cells from excess In vitro fertilization (IVF) embryos, and also allows for the creation of human embryos for research.

Check

Assess your diabetes risk

Quiz

Am I at risk for COPD?

Ask

CyberDoc

Link:
Breakthrough: Doctors can now 'edit' genes in human embryos - Health24