So... how about them FOXL2 and DMRT1 genes?
Folks who think it'd be neat for people to be able to choose their biological sex take note; apparently Testes can become Ovaries, and Ovaries can become Testes (complete with the expected hormones, and the possibility of even reproductive cells), based on the balance of two competing sex-determination proteins coded by these genes. And this switch can happen even in adulthood, across most (all?) species that have sexes, and in a reversible fashion.
Mammalian sex determination initiates in the fetal gonad with specification of bipotential precursor cells into male Sertoli cells or female granulosa cells. This choice was long presumed to be irreversible, but genetic analysis in the mouse recently revealed that sexual fates must be maintained throughout life. Somatic cells in the testis or ovary, even in adults, can be induced to transdifferentiate to their opposite-sex equivalents by loss of a single transcription factor, DMRT1 in the testis or FOXL2 in the ovary.
FOXL2 versus SOX9: A lifelong ‘‘battle of the sexes’’DMRT1 prevents female reprogramming in the postnatal mammalian testisNormally, bodies have both of these genes coding for their proteins, but a competitive feedback system keeps it tipped in favor of whichever protein is currently in dominance. However, by deactivating one of these genes, or potentially by using supplements to make the other protein more prevalent in the bloodstream, it tips a feedback system in favor of that protein's production, causing that person's jumblies to become the other kind of jumblies; Ovaries to become Testes (FOXL2 > DMRT1) or Testes to become Ovaries (DMRT1 > FOXL2). Looking at other studies, it's an old biological mechanism, probably as old as Sex Differentiation itself, since it's found as far back as our common ancestor with flatworms and insects. I'd hazard a guess the organisms that can switch their expressed sex during their lifetime (lots of fish and amphibians, and some insects) evolved a way to control this system. One theory is that this competetive feedback loop that keeps production tipped strongly in favor of one or the other separately from their genome seems to be a failsafe for keeping biological sex binary, and in keeping mutations in sex-determination from producing sterile intersex adults in some cases.
Apart from knocking out these genes to induce a sex change, I believe this means we could create a sort of medication to switch the gender expression of a person's reproductive organs back and forth, along with the appropriate hormonal effects, by synthesizing these proteins artificially (say, bacterial protein factories with FOXL2/DMRT1 genes inserted). I am excited for the future when choosing what biological sex you want to express is a simple thing, but some of the other possibilities are pretty crazy and cool too.
A few possible applications for this research, off the top of my head:
- We could treat infertility related to intersex conditions, as well as mutations of FOXL2/DMRT1 that produce malfunctioning versions of these proteins. A lot of people deal with infertility, and this could be a major breakthrough in treatment.
- Same-sex partners looking to have children could potentially use a therapy like this to switch their junk to opposite-sex junk temporarily, make their own complimentary gametes, and use in-vitro techniques to produce biological offspring as though they were opposite-sex. So you could literally have 2 biological dads/moms. Raises some ethical concerns, in that 2 female parents would only produce female children, and 2 male parents would result in 25% of pregnancies being non-viable YYs. I've no idea if male Y-Chromosome eggs would be viable either, if their cellular functions need genes found on the X Chromosome... but even if so, it still would create new options for same-sex couples.
- It enables people, especially younger people, to choose the sex their body will express physically in a way that doesn't require hormone supplements. Transgender persons could switch their body's physical sex, even keep their existing jumblies, and switch them into other-sex mode. For post-puberty trans-folks, this wouldn't remove most of their existing physical characteristics, but it would induce new hormone-based secondary sex characteristics like voice-dropping and facial hair, or breast development, etc. Also, paired with advances in surgery, they could get fully functional reproductive organs that match the sex they identify with too.
- People could potentially create an in-vitro child entirely by themselves. Said child would be a complete genetic clone. ._.