The Y Chromosome and Its Role in Primary Sex Differentiation

Male differentiation is triggered by mal gene coding for a zinc finger protein (termed a Y chromosomal gene, termed TDF. During the ZFY) was isolated from the testis determining last 25 yr several hypotheses have been formuregion of the human and mouse Y chromosome. lated regarding the nature of TDF and its gene Due to its location and possible function as a product. Serologically detectable H-Y antigen, also transcription factor ZFY was considered a candireferred to as serologically detectable male (SDM) date of TDF. ZFY, however, has been demonantigen, was considered a candidate of a testis strated not to be TDF. Another Y chromosomal determining factor. It has now been shown that gene, S R Y (for sex-determining region Y) now testis-secreted SDM is the same as the Miillerian seems to be a likely candidate of TDF. It is inhibiting substance (MIS) and therefore has no expressed during the critical period of sex differenprimary role in testis differentiation. Similarly, the tiation in the somatic cells of the developing testis transplantation H-Y antigen does not induce tesof the mouse and it induces sex reversal of ticular development. More recently, a Y chromosotransgenic mice.