The two candidate testis-determining Y genes (Zfy-1 and Zfy-2) are differentially expressed in fetal and adult mouse tissues.

The candidate testis-determining Y genes of the mouse Zfy-1 and Zfy-2, encode proteins containing an acidic amino terminus and a carboxyl terminus composed of 13 zinc fingers. The zinc finger domain is conserved among human and mouse zinc finger X and Y genes. We report a 6-amino-acid deletion in the Zfy-2 zinc finger domain of laboratory mice possessing musculus Y chromosomes. The effect of this deletion on the function of Zfy-2 is not known. The reverse transcriptase-polymerase chain reaction (RT-PCR) and Northern blot techniques were used to study expression of Zfy in adults and fetuses. In adults, the data suggest that Zfy-1 and Zfy-2 transcription is linked to spermatogenesis, that transcription increases with the initiation of meiosis, and that high levels of these mRNAs are found in postmeiotic round spermatid cells. The data also suggest that differential expression of these two genes is present with expression of Zfy-2 being slightly greater than Zfy-1. In fetuses, Zfy transcripts were detected in several tissues, including the testes. In contrast to the situation in adults, the data suggest that expression of Zfy-1 is greater than that of Zfy-2. The data suggesting that Zfy-1 expression is present in fetal testes support the hypothesis that this gene plays a role in testis differentiation. However, because the Zfy genes are apparently also expressed during spermatogenesis and in fetal organs other than testes, they may serve additional functions besides their postulated role in testis determination.