New candidate genes identified for controlling mouse gonadal sex determination and the early stages of granulosa and Sertoli cell differentiation.

Mammalian gonadal sex-determining (GSD) genes are expressed in a unique population of somatic cells that differentiate into granulosa cells in XX gonads or Sertoli cells in XY gonads. The ability to efficiently isolate these somatic support cells (SSCs) during the earliest stages of gonad development would facilitate identifying 1) new candidate GSD genes that may be involved in cases of unexplained abnormal gonad development and 2) genes involved in the earliest stages of granulosa and Sertoli cell differentiation. We report the development of a unique mouse carrying two transgenes that allow XX and XY mice to be distinguished as early as Embryonic Day 11.5 (E11.5) and allow SSCs to be isolated from undifferentiated (E11.5) and early differentiated (E12.5) fetal gonads. The Mouse Genome 430v2.0 GeneChip (Affymetrix) was used to identify transcripts exhibiting a sexual dimorphic expression pattern in XX and XY isolated SSCs. The analysis revealed previously unidentified sexually dimorphic transcripts, including low-level expressed genes such as Sry, a gene not identified in other microarray studies. Multigene real-time PCR analysis of 57 genes verified that 53 were expressed in fetal gonads in a sexually dimorphic pattern, and whole-mount in situ hybridization analysis verified 4930563E18Rik, Pld1, and Sprr2d are expressed in XX gonads, and Fbln2, Ppargc1a, and Scrn1 are expressed in XY gonads. Taken together, the data provide a comprehensive resource for the spatial-temporal expression pattern of genes that are part of the genetic network underlying the early stages of mammalian fetal gonadal development, including the development of granulosa and Sertoli cells.