Developmental changes in inhibin-α gene expression in the mouse testis

Inhibin is a gonadal hormone which is composed of an α-subunit and one of two related β-subunits (β_A, β _B). Inhibin is important for pituitary FSH regulation, normal follicle development and maintenance of the estrous cycle in the female, whereas the role of inhibin in the male is less clear. Thus, we examined the expression of the inhibin-α gene in testis during sexual maturation in male mice, to try to gain insight into its functions in the male. Male mice of the ICR strain attained fertility at 6 weeks of age, and histological analysis revealed that a functional testis was formed, with seminiferous tubules which contain mature sperm and with an abundant population of Leydig cells. Parallel with this sexual maturation, inhibin-α subunit protein synthesis increased, whereas synthesis of the activin β_A and activin β _B followed with a delayed time course. Inhibin-α mRNA also increased during this critical period, and this corresponded to a change in the methylation status of the inhibin-α gene. Taken together, our data reveal that activation of inhibin-α gene during testis development correlated with the histological maturation of the testis and the acquisition of fertility in male mice.