Submicroscopic deletions in the Y chromosome of infertile men.

Recent investigations have suggested a high prevalence of Y chromosome submicroscopic deletions in men with severely impaired spermatogenesis. We evaluated the frequency of Y chromosome deletions in 160 infertile men using a series of 36 sequence-tagged-sites, emphasizing intervals 5 and 6 of the long arm of the Y chromosome. Peripheral leukocyte DNA was extracted and amplified with two parallel techniques to minimize potential overestimation of the frequency of deletions. The presence of deletions was evaluated relative to patient's sperm concentration, testis volume, and hormonal parameters. Men with sperm concentration <5 x 10(6)/ml had a 7% prevalence of submicroscopic Y chromosome deletions. Deletions were detected in 7% of azoospermic men, 10% of men with <1 x 10(6) spermatozoa/ml, and 8% of men with >1 x 10(6) but <5 x 10(6) spermatozoa/ml. Other clinical parameters did not identify men with Y chromosome deletions prior to polymerase chain reaction (PCR)-based testing for the presence of sequence-tagged-sites. Two distinct regions of Y chromosome deletions were detected, approximately 3.6 Mb and 1.4 Mb in length respectively. These deleted regions are present in AZFb and AZFc respectively. No deletions were detected in AZFa. The loss of these two distinct areas is supported by the finding of highly repetitive sequences along the Y chromosome, predisposing to deletion of specific intervals on the Y chromosome during meiosis. Men with severe male infertility are at high risk for Y chromosome deletions. Testing of men for these genetic abnormalities is indicated prior to treatment with assisted reproduction.