How to make a gonad: cellular mechanisms governing formation of the testes and ovaries.

Sex determination of the gonad is an extraordinary process by which a single organ anlage is directed to form one of two different structures, a testis or an ovary. Morphogenesis of these two organs utilizes many common cellular events; differences in the timing and execution of these events must combine to generate sexually dimorphic structures. In this chapter, we review recent research on the cellular processes of gonad morphogenesis, focusing on data from mouse models. We highlight the shared cellular mechanisms in testis and ovary morphogenesis and examine the differences that enable formation of the two organs responsible for the perpetuation of all sexually reproducing species.