PCR analysis of the Y chromosome long arm in azoospermic patients: evidence for a second locus required for spermatogenesis.

We analyzed DNA from 63 Japanese men with either azoospermia or severe oligospermia whose Y chromosomes were cytogenetically normal. A total of 16 loci were examined: 15 loci on the long arm between DYS7E and DYZ1, and the YRRM1 locus, a candidate gene for the azoospermic factor, AZF. One patient with a pericentric inversion of the Y chromosome was also included. We detected micro-deletions in ten individuals. The YRRM1 gene was involved in only three of them. The remaining seven patients showed deletion between DYS7C and DYS239 in common, indicating the presence of at least one additional gene, deletion of which causes azoospermia.