THE HUMAN DAZ GENES, A PUTATIVE MALE-INFERTILITY FACTOR ON THE Y-CHROMOSOME, ARE HIGHLY POLYMORPHIC IN THE DAZ REPEAT REGIONS

The DAZ genes on the human Y Chromosome (Chr) are strong candidates fo r the azoospermia factor AZF. They are frequently deleted in azoosperm ic or severely oligospermic males and are expressed exclusively in ger m cells. In addition, the DAZ genes share a high degree of similarity with a Drosophila male infertility gene, boule. The predicted DAZ prot eins contain an RNA recognition motif (RRM), and multiple copies of a repeat (the DAZ repeat) in tandem array. To understand the DAZ gene fa mily and its expression, the DAZ genomic structure and RNA transcripts in numerous males, as well as several DAZ cDNA clones were analyzed. The results of genomic Southern blot showed that each male contains mu ltiple DAZ genes with varying numbers of DAZ repeats, and that the cop y number of the DAZ repeats are polymorphic in the population. The pre sence of multiple species of DAZ transcripts with different copy numbe r and arrangement of the DAZ repeats in an individual suggests that mo re than one DAZ gene are transcribed. The existence of multiple functi onal DAZ genes complicates the analysis of genotype/phenotype correlat ions among males with varying sperm counts.