Estrogen-Regulated Genes in Rat Testes and Their Relationship to Recovery of Spermatogenesis

Despite numerous observations of effects of estrogens on spermatogenesis, identification of estrogenregulated genes in the testis is limited. We previously showed in rats, in which irradiation had completely blocked spermatogonial differentiation, that testosterone (T) suppression with GnRH-antagonist and antiandrogen stimulated spermatogenic recovery and addition of estradiol (E2) to this regimen accelerated this recovery. We report here the global changes in testicular cell gene expression induced by the E2 treatment. By minimizing the changes in other hormones and using concurrent data on the regulation of the genes by those hormones, we were able to dissect the effects of estrogen on gene expression, independent of gonadotropin or T changes. Expression of 20 genes, largely in somatic cells, was up- or down-regulated between 2- and 5-fold by E2. The unexpected and striking enrichment of transcripts not corresponding to known genes among the E2-downregulated probes suggested that these might represent non-coding mRNAs; indeed we have identified several as micro-RNAs, as well as their potential target genes in this system. We propose that genes whose expression levels are altered in one direction by irradiation and in the opposite direction by both T suppression and E2 treatment are candidates for controlling the block in differentiation. Several genes, including insulin-like 3 (Insl3), satisfied those criteria. If they are indeed involved in the inhibition of spermatogonial differentiation, they may be candidate targets for treatments to enhance recovery of spermatogenesis following gonadotoxic exposures, such as those resulting from cancer therapy.