Female sperm

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Female sperm is a term that traditionally refers to a sperm that contains an X chromosome (since when such a sperm fertilizes an egg, a female daughter is born) produced, in the usual way by a male. However, for over 20 years, dating back to the late 1980s, scientists have explored how to produce sperm where all of the chromosomes come from an adult woman.^[1] In the late 1990s, theory become a partial reality when scientists in Japan developed chicken female sperm, by injecting bone marrow stem cells from a female chicken into a male chicken's testicles. This technique has not yet been successfully adapted for use by humans.

1 Female sperm production using testicular transplantation and artificial Y chromosomes
2 Bone marrow stem cell conversion
3 Same-sex marriage
4 See also
5 References

[edit] Female sperm production using testicular transplantation and artificial Y chromosomes

Creating female sperm was first raised as a possibility in a patent filed in 1991^[2] 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.^[3] These simple transplantation methods follow from earlier observations by developmental biologists that germ stem cells 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. Normally, 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 won't 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 of a time 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 don't 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^[4] on methods for creating human female sperm using artificial or natural Y chromosomes and testicular transplantation.^[5] Key to successful creation of female sperm (and male eggs) will be inducing male epigenetic markings for female cells that initially have female markings, with techniques for doing so disclosed in the patent application.^[6]

[edit] Bone marrow stem cell conversion

Scientists from the University of Newcastle-upon-Tyne led by biologist Karim Nayernia 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 if such techniques can be used to make female sperm.^{[citation needed]}

[edit] Same-sex marriage

If created, a "female sperm" cell could fertilize an egg cell, a procedure which, among other potential applications, might enable female same-sex couples to produce a child which would be the biological offspring of its two mothers.^[7]^[8]^[9]^[10]^[11]^[12]

Given the importance of procreation to critics of same sex marriage,^[13] the development of human female sperm and children so born may alter the debate.