Single-cell exploration of gonadal somatic cell lineage specification during human sex determination.

Gonad development is an exciting model to study cell fate commitment. A better understanding of sex determination requires the identification of all involved cell types and their dynamic expression programs. Here, we present an atlas of 128,000 single cells from human gonads between 5 and 12 post-conceptional weeks. A focused analysis of somatic cells uncovered a population of bipotential progenitors derived from the coelomic epithelium of both testes and ovaries, which may have the capacity to commit to either a steroidogenic or a supporting fate. Moreover, our analyses suggest that early supporting cells, prior to differentiation into Sertoli or pre-granulosa cells, also give rise to the rete testis/ovarii and that the ovary retains the capacity to feed the supporting cell pool for an extended period of time, directly from the surface epithelium. Finally, the potential involvement of the gonadotropin releasing hormone (GnRH) signaling pathway in regulating testis differentiation was assessed ex vivo.