Cytoplasmic transfer
Encyclopedia
Cytoplasmic transfer is an assisted reproductive technology
(ART), fertility technique whereby cytoplasm
from a donor egg is injected into an egg with compromised mitochondria
. The resulting egg is then fertilized
with sperm
and implanted
in a womb
, usually that of the woman who provided the recipient egg and nuclear DNA
.
fragmentation and overall poor embryo development. The incidence of compromised mitochondria increases with advanced maternal age
, thought to occur near the age of thirty-five. Consequently, it has been found advantageous for young women to donate cytoplasm to older women, creating rejuvenated eggs. This is particularly desirable for couples or women who wish to genetically contribute to any resulting embryo, given cytoplasmic transfer does not interfere with the primary nuclear DNA input from the recipient egg.
present from the donor. Children conceived through this process occasionally test positive for genetic material from three parents. It is therefore arguably the first example of germ line genetic modification (manipulation that affects future generations) of humans. Because of the chance for mitochondrial DNA transfer, the embryo may also be exposed to numerous diseases connected with mitochondrial DNA such as diabetes, Lou Gehrig's disease, and pervasive developmental disorders. There is much concern associated with the potential transfer of mitochondrial DNA and its unknown interaction with the foreign DNA of the recipient egg. There is also no data as to the health of maturing children conceived through cytoplasmic transfer, the first successful birth having occurred in 1997 at Saint Barnabas Medical Center
in Livingston, New Jersey
as a result of procedure performed by The Institute for Reproductive Medicine and Science..
, worried about the long-term effects of creating genetic hybrids, asserted regulatory authority over cytoplasmic transfer, in effect banning the procedure in the U.S. until lengthy and extensive studies can be conducted. There is dispute as to the extent of the FDA's jurisdiction
over reproductive technologies and federal law is inconclusive. The FDA claims that genetically manipulated embryos constitute a "biological product" and are therefore subject to regulation similar to medical implements and drugs. In any case, the withholding of federal funds and prohibitively expensive research costs needed to fulfill FDA regulations has resulted in movement of cytoplasmic transfer operations abroad. This has contributed to the development of reproductive tourism where infertile couples or individuals travel in order to obtain fertility
treatments banned in their home country or state.
Assisted reproductive technology
Assisted reproductive technology is a general term referring to methods used to achieve pregnancy by artificial or partially artificial means. It is reproductive technology used primarily in infertility treatments. Some forms of ART are also used in fertile couples for genetic reasons...
(ART), fertility technique whereby cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
from a donor egg is injected into an egg with compromised mitochondria
Mitochondrion
In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 1.0 micrometers in diameter...
. The resulting egg is then fertilized
Fertilisation
Fertilisation is the fusion of gametes to produce a new organism. In animals, the process involves the fusion of an ovum with a sperm, which eventually leads to the development of an embryo...
with sperm
Sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...
and implanted
Implant (medicine)
An implant is a medical device manufactured to replace a missing biological structure, support a damaged biological structure, or enhance an existing biological structure. Medical implants are man-made devices, in contrast to a transplant, which is a transplanted biomedical tissue...
in a womb
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
, usually that of the woman who provided the recipient egg and nuclear DNA
Nuclear DNA
Nuclear DNA, nuclear deoxyribonucleic acid , is DNA contained within a nucleus of eukaryotic organisms. In mammals and vertebrates, nuclear DNA encodes more of the genome than the mitochondrial DNA and is composed of information inherited from two parents, one male, and one female, rather than...
.
Candidates
Cytoplasmic transfer was created to aid women who experience infertility due to deficient or damaged mitochondria, contained within an egg's cytoplasm. Deficient mitochondria can lead to recurrent implantation failure, high levels of embryoEmbryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
fragmentation and overall poor embryo development. The incidence of compromised mitochondria increases with advanced maternal age
Advanced maternal age
Advanced maternal age is defined as an increase in the age at which women give birth to their first child, is now a widespread, and indeed near universal, phenomenon across the OECD countries....
, thought to occur near the age of thirty-five. Consequently, it has been found advantageous for young women to donate cytoplasm to older women, creating rejuvenated eggs. This is particularly desirable for couples or women who wish to genetically contribute to any resulting embryo, given cytoplasmic transfer does not interfere with the primary nuclear DNA input from the recipient egg.
Risks
Though cytoplasmic transfer does not involve the transfer of nuclear DNA, there may still be a small amount of mitochondrial DNAMitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
present from the donor. Children conceived through this process occasionally test positive for genetic material from three parents. It is therefore arguably the first example of germ line genetic modification (manipulation that affects future generations) of humans. Because of the chance for mitochondrial DNA transfer, the embryo may also be exposed to numerous diseases connected with mitochondrial DNA such as diabetes, Lou Gehrig's disease, and pervasive developmental disorders. There is much concern associated with the potential transfer of mitochondrial DNA and its unknown interaction with the foreign DNA of the recipient egg. There is also no data as to the health of maturing children conceived through cytoplasmic transfer, the first successful birth having occurred in 1997 at Saint Barnabas Medical Center
Saint Barnabas Medical Center
Saint Barnabas Medical Center , an affiliate of the Barnabas Health , is a 597-bed non-profit major teaching hospital located in Livingston, New Jersey...
in Livingston, New Jersey
Livingston, New Jersey
Livingston is a township in Essex County, New Jersey, United States. As of the United States 2000 Census, the township population was 29,366.Livingston was incorporated as a township by an Act of the New Jersey Legislature on February 5, 1813, from portions of Caldwell Township and Springfield...
as a result of procedure performed by The Institute for Reproductive Medicine and Science..
Legal status
In 2001, the Food and Drug AdministrationFood and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
, worried about the long-term effects of creating genetic hybrids, asserted regulatory authority over cytoplasmic transfer, in effect banning the procedure in the U.S. until lengthy and extensive studies can be conducted. There is dispute as to the extent of the FDA's jurisdiction
Jurisdiction
Jurisdiction is the practical authority granted to a formally constituted legal body or to a political leader to deal with and make pronouncements on legal matters and, by implication, to administer justice within a defined area of responsibility...
over reproductive technologies and federal law is inconclusive. The FDA claims that genetically manipulated embryos constitute a "biological product" and are therefore subject to regulation similar to medical implements and drugs. In any case, the withholding of federal funds and prohibitively expensive research costs needed to fulfill FDA regulations has resulted in movement of cytoplasmic transfer operations abroad. This has contributed to the development of reproductive tourism where infertile couples or individuals travel in order to obtain fertility
treatments banned in their home country or state.
External links and references
- Pregnancy after cytoplasmic transfer in a couple suffering from idiopathic infertility, Human Reproduction, Vol.17, No.7
- Bloodlines Timeline
- Reproductive Tourism and the Regulatory Map The New England Journal of Medicine, 10 Feb, 2005
- http://news.yahoo.com/s/ap/20080205/ap_on_sc/embryo_research
- http://www.gene-watch.org/genewatch/articles/200207_worldwatch_levine.pdf
- Cytoplasmic transfer in assisted reproduction