Here is a new paper from the Yamamoto lab looking at the function of fru in individual brain neurons. This is is clearest evidence to date that FruM controls sex-specific differentiation on individual neurons through a transcription-dependent mechanisms. Another interesting possibility emerging from this paper is that the male- and female-specific differentiation programs are “pre-wired” into the neurons, and that FruM is needed to flip the switch between these programs but not to specify either. This seems remarkably similar to the role of Dsx in the gonad and external genitalia. Check it out.