Characterization of HSFY, a novel AZFb gene on the Y chromosome with a possible role in human spermatogenesis.

HSFY (heat shock transcription factor, Y chromosome) has been mapped in the AZFb region of the Y chromosome, whose deletion results in severe male infertility. HSFY belongs to the heat shock factor family that has been shown to be implicated in spermatogenesis both in animals and humans. We report the characterization of the genomic structure, the number of copies on the Y chromosome and the expression of the gene. By comparison of data obtained from expression analysis and from GenBank cDNA sequences, seven exons were identified. Alternative splicing generates three different transcripts and proteins, each containing an HSF domain typical of HSF proteins. Two identical and functional full-length copies of HSFY map in palindrome P4 of AZFb, whereas four similar sequences mapping in two clusters in palindrome P1 of AZFc and P3 seem to represent pseudogenes. Sequences similar to few HSFY exons are also located in the short arm of chromosomes Y, X and 22. Expression analysis revealed that the three HSFY transcripts are differentially expressed, transcript 1 being present in many tissues including testis and ejaculated sperm, and transcripts 2 and 3 being testis-specific. These data suggest that HSFY could have an important role in human spermatogenesis.