The identification and characterization of genes with potential roles in fetal ovary development

Improper gonad differentiation can lead to conditions ranging from reduced fertility to sex reversal. In mammals, Sry (sex determining region, Y chromosome) initiates testis development by directing supporting cell precursors to differentiate into testicular Sertoli cells rather than ovarian granulosa cells. How ovary development is initiated is poorly understood, and we sought to gain a better understanding of fetal ovary development by identifying cell-type-specific genes that might be involved in ovarian somatic cell differentiation.; Our lab previously developed Sry-EGFP transgenic mice that express enhanced green fluorescent protein uniquely in the supporting cell lineage of both male and female gonads. This transgene is the earliest known specific marker of these cells. Using fluorescence-activated cell sorting, we negatively selected against CD31+ germ and endothelial cells, and isolated EGFP+/CD31-pre-granulosa cells and EGFP-/CD31-somatic cells from E13.5 Sry-EGFP transgenic ovaries. Using microarrays to compare gene expression between these two cell populations, we identified 471 differentially expressed genes. Ten genes were selected based on their potential for being regulators of gonadogenesis for further analysis using RT-PCR, immunohistochemistry, and in situ hybridization to characterize their expression in normal fetal gonads, as well as in gonads with mutations that cause abnormal ovary differentiation.; Several of the characterized genes were expressed in patterns suggestive of a role in fetal ovary and/or testis development. 1700106J16Rik and Sprr2d, two genes that appeared to be specifically expressed in the supporting cell lineage with a female bias at the initial stages of ovary differentiation, were analyzed in detail. Their expression patterns were suggestive of roles in ovarian pre-granulosa cell differentiation. In XX gonads, Sprr2d was downregulated in a spatial pattern resembling that of germ cell differentiation; therefore, a potential link to meiosis in germ cells was explored. In XY gonads, 1700106J16Rik and Sprr2d expression patterns were identical to that of Sry, suggesting that these three genes may be co-regulated. Our observations are consistent with a model for mammalian sex determination wherein the testicular and ovarian pathways are initiated simultaneously within the supporting cell lineage.