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Abstract:
Inhibin (INH) is a gonadal glycoprotein hormone that regulates pituitary FSH secretion and may also play a role in the regulation of androgen biosynthesis. There are two forms of inhibin that strongly inhibit pituitary FSH secretion. These share the same α subunit that is covalently linked to one of two distinct β subunits (βA or βB. However, dimers of two β subunits are potent stimulators of FSH synthesis and release in vitro. The β subunits share extensive sequence similarity with transforming growth factor β. Recently isolated cDNAs for all three inhibin subunits have been used to map their cognate loci on human and mouse chromosomes by Southern blot analysis of somatic cell hybrid DNAs and by in situ hybridization. INHα and INHβB genes were assigned to human chromosome 2, regions q33 → qter and cen → q13, respectively, and to mouse chromosome 1. The INHβA locus was mapped to human chromosome 7p15 → p14 and mouse chromosome 13. The region of mouse chromosome 1 that carries other genes known to have homologs on human chromosome 2q includes the jsd locus (for juvenile spermatogonial depletion). Adult mice have elevated levels of serum FSH and their testes are devoid of spermatogonial cells. The possibility that the mutation in jsd involves the INHα or INHβB gene was investigated by Southern blotting of DNA from mice, and no major deletions or rearrangements were detected.
