Female sperm
Encyclopedia
Female Sperm is a term that refers to a sperm that contains an X chromosome
, produced in the usual way by a male, referring to the fact that when such a sperm fertilizes an egg, a female child is born. However, since the late 1980s, scientists have explored how to produce sperm whereby all of the chromosomes come from an adult woman. In the late 1990s, this concept became a partial reality when scientists in Japan developed chicken female sperm by injecting bone marrow
stem cell
s from a female chicken into a rooster's testicles. This technique proved to fall below expectations, however, and has not yet been successfully adapted for use on humans.
s are autonomous in the sense that they can begin the processes to become both sperm and eggs.
One potential roadblock to injecting a woman's cells into a man's testicles is that the man's immune system might attack and destroy the woman's cells. In usual circumstances, when foreign cells (such as cells/organs from other people, or infectious bacteria) are injected into the human body, the immune system will reject such cells. However, a special property of a man's testicles is that they are immune-privileged
, that is, a man's immune system will not attack foreign cells (such as a woman's cells) injected into the sperm-producing part of the testicles. Thus, a woman's cells will remain in the man's testicles long enough to be converted into sperm.
However, there are more serious roadblocks. Biologists have well established that male sperm production relies on certain genes on the Y chromosome
, which, when missing or defective, lead to such men producing little to no sperm in their testicles. An analogy, then, is that a cell from a woman suffers from complete Y chromosome deficiency. While many genes on the Y chromosome have backups (homologs) on other chromosomes, a few genes such as RBMY on the Y chromosome do not have such backups, and their effects are needed to be compensated for to convert cells from a woman into sperm. In 2007, a patent application was filed on methods for creating human female sperm using artificial or natural Y chromosomes and testicular transplantation. Key to successful creation of female sperm (and male egg
s) will be inducing male epigenetic markings for female cells that initially have female markings, with techniques for doing so disclosed in the patent application.
discovered a method of creating partly developed sperm cells, otherwise known as "spermatogonial" stem cells, from the bone marrow of both sexes, entirely in-vitro (outside the human body), and is seeking funding to see whether such techniques can be used to make female sperm.
X chromosome
The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...
, produced in the usual way by a male, referring to the fact that when such a sperm fertilizes an egg, a female child is born. However, since the late 1980s, scientists have explored how to produce sperm whereby all of the chromosomes come from an adult woman. In the late 1990s, this concept became a partial reality when scientists in Japan developed chicken female sperm by injecting bone marrow
Bone marrow
Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...
stem cell
Stem cell
This article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...
s from a female chicken into a rooster's testicles. This technique proved to fall below expectations, however, and has not yet been successfully adapted for use on humans.
Female sperm production
Creating female sperm was first raised as a possibility in a patent filed in 1991 by injecting a woman's cells into a man's testicles, though the patent focused mostly on injecting altered male cells into a man's testicles (to correct genetic diseases). In 1997, Japanese scientists partially confirmed such techniques by creating chicken female sperm in a similar manner. "However, the ratio of produced W chromosome-bearing (W-bearing) spermatozoa fell substantially below expectations. It is therefore concluded that most of the W-bearing PGC could not differentiate into spermatozoa because of restricted spermatogenesis." These simple transplantation methods follow from earlier observations by developmental biologists that germ stem cellStem cell
This article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...
s are autonomous in the sense that they can begin the processes to become both sperm and eggs.
One potential roadblock to injecting a woman's cells into a man's testicles is that the man's immune system might attack and destroy the woman's cells. In usual circumstances, when foreign cells (such as cells/organs from other people, or infectious bacteria) are injected into the human body, the immune system will reject such cells. However, a special property of a man's testicles is that they are immune-privileged
Immune privilege
Immune privilege is a term used to describe certain sites in the body which are able to tolerate the introduction of antigen without eliciting an inflammatory immune response. Tissue grafts are normally recognised as foreign antigen by the body and attacked by the immune system...
, that is, a man's immune system will not attack foreign cells (such as a woman's cells) injected into the sperm-producing part of the testicles. Thus, a woman's cells will remain in the man's testicles long enough to be converted into sperm.
However, there are more serious roadblocks. Biologists have well established that male sperm production relies on certain genes on the Y chromosome
Y chromosome
The Y chromosome is one of the two sex-determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs...
, which, when missing or defective, lead to such men producing little to no sperm in their testicles. An analogy, then, is that a cell from a woman suffers from complete Y chromosome deficiency. While many genes on the Y chromosome have backups (homologs) on other chromosomes, a few genes such as RBMY on the Y chromosome do not have such backups, and their effects are needed to be compensated for to convert cells from a woman into sperm. In 2007, a patent application was filed on methods for creating human female sperm using artificial or natural Y chromosomes and testicular transplantation. Key to successful creation of female sperm (and male egg
Male egg
Male eggs are the result of a process in which the eggs of a female would be emptied of their genetic contents , and those contents would be replaced with male DNA. Such eggs could then be fertilized by sperm. The procedure was conceived by Dr. Calum MacKellar, a Scottish bioethicist...
s) will be inducing male epigenetic markings for female cells that initially have female markings, with techniques for doing so disclosed in the patent application.
Bone marrow stem cell conversion
Scientists from the University of Newcastle-upon-Tyne led by biologist Karim NayerniaKarim Nayernia
Karim Nayernia is an Iranian biomedical scientist and a world expert on stem cell biology.He carried out pioneering work that has the potential to lead to future therapies for a range of medical conditions such as heart disease, Parkinson's disease and male infertility...
discovered a method of creating partly developed sperm cells, otherwise known as "spermatogonial" stem cells, from the bone marrow of both sexes, entirely in-vitro (outside the human body), and is seeking funding to see whether such techniques can be used to make female sperm.