Physical gender is apparently more fluid than we anticipated. New paper from NIMR: they showed that knocking out the Foxl2 gene from the ovaries of adult mice not only made the ovaries stop working as such, but they switched over and started to become testicle-like. Not actually manufacturing sperm, but they do start manufacturing male rather than female hormones.
NB that was in adult mice; apparently some of the key sex-differentiation pathways don’t shut off after the basic organs are built. Which isn’t entirely surprising given the existence of sex-changing fish, but still pretty damned surprising given that these are mammals.
This has some very interesting potential applications, especially for those with gender dysphoria. (Imagine being able to switch some parts over in situ rather than needing regular hormone injections?) It also really increases my curiosity about gender dysphoria; now that we’re starting to get a clearer picture of the various stages involved in determining physical gender, it would be really interesting to see if anomalies in any of these stages were correlated with dysphoria later in life.