A long-range restriction map of deletion interval 6 of the human Y chromosome: a region frequently deleted in azoospermic males

Deletion interval 6 (DI6) of the human Y chromosome, located at the distal end of the long arm euchromatic region, is required for normal spermatogenesis. About 10% of males with idiopathic azoospermia or oligospermia have microdeletions in this region. Six gene families, including RBMY (RNA binding motif, Y chromosome), DAZ (deleted in azoospermia), and four recently isolated genes, have been mapped to this interval. Genes from all of these families show testis-specific expression and are thus candidates for azoospermic factor (AZF). DI6 is also rich in Y-specific repetitive sequences, which may be responsible for its frequent deletion. To understand the sequence organization of this region, a 5-Mb restriction map was constructed based on YAC clones and was partially verified on genomic DNA. The locations of five gene family members, as well as numerous STSs, were determined. The map shows several inverted and direct repeats several hundred kilobases in size. The restriction map of DI6 will facilitate future mapping of deletion breakpoints in infertile males and elucidation of mechanisms behind frequent deletions.