SUBSTANTIAL PREVALENCE OF MICRODELETIONS OF THE Y-CHROMOSOME IN INFERTILE MEN WITH IDIOPATHIC AZOOSPERMIA AND OLIGOZOOSPERMIA DETECTED USING A SEQUENCE-TAGGED SITE-BASED MAPPING STRATEGY

Genes on the long arm of Y (Yq), particularly within interval 6, are b elieved to play a critical role in human spermatogenesis. Cytogenetica lly detectable deletions of this region are associated with azoospermi a in men, but are relatively uncommon. It has been hypothesized that m icrodeletions of Yq may account for a significant proportion of men wi th infertility. The objective of this study was to validate a sequence -tagged site (STS)-mapping strategy for the detection of Yq microdelet ions and to use this method to determine the proportion of men with id iopathic azoospermia or severe oligozoospermia who carry microdeletion s in Yq. STS mapping of a sufficiently large sample of infertile men s hould also help further localize the putative gene(s) involved in the pathogenesis of male infertility. Genomic DNA was extracted from perip heral leukocytes of 16 normal fertile men, 7 normal fertile women, 60 infertile men (50 of whom had azoospermia and 10 of whom had severe ol igozoospermia with no other recognizable cause of infertility), and 15 patients with the X-linked disorder, ichthyosis. PCR primers were syn thesized for 26 STSs that span Yq interval 6. None of the 16 normal me n of known fertility had microdeletions. Seven normal fertile women fa iled to amplify any of the 26 STSs, providing evidence of their Y spec ificity. No microdeletions were detected in any of the 15 patients wit h ichthyosis. Of the 60 infertile men typed with 26 STSs, 11 (18%; 10 azoospermic and 1 oligozoospermic) failed to amplify 1 or more STS. In terestingly, 4 of the 11 patients had microdeletions in a region that is outside the Yq region from which the DAZ (deleted in azoospermia ge ne region) gene was cloned. In an additional 3 patients, microdeletion s were present both inside and outside the DAZ region. In 3 subjects, the microdeletions were verified by Southern analysis using labeled PC R products corresponding to the deleted STSs as probes. These data sug gest a high prevalence (18%) of Yq microdeletions in men with idiopath ic azoospermia/severe oligospermia. The physical locations of these mi crodeletions provide further support for the concept that a gene(s) on Yq deletion interval 6 plays an important role in spermatogenesis. Th e presence of deletions that do not overlap with the DAZ region sugges ts that genes other than the DAZ gene may also be implicated in the pa thogenesis of some subsets of male infertility.