Background: AZFc on human Y chromosome has been found to be functionally important in spermatogenesis. Complete AZFc deletion is one of the most frequent causes of male infertility, while roles of partial AZFc deletions (gr/gr deletion and b2/b3 deletion) in spermatogenesis are controversial.
Methods: To further study the roles of partial AZFc deletions in spermatogenic impairment and the relationship between complete and partial AZFc deletions, we typed these deletions, did quantitative analysis of DAZ gene copies, and performed Y chromosome haplogrouping in seven pedigrees of complete AZFc deletion carriers, 296 infertile and 280 healthy men in Chinese.
Results: Neither gr/gr deletion nor b2/b3 deletion was found to be associated with spermatogenic failure. In one pedigree, we observed that a complete AZFc deletion was derived from gr/gr deletion, suggesting that complete deletions of AZFc can be preceded with partial deletions. In addition, we identified a new gr/gr-deleted Y haplogroup Q1 and confirmed the reported fixation of b2/b3 deletion in hg N as well. We also showed that the frequency of complete AZFc deletion in hg Q1 and N was significantly higher than that in the other haplogroups with less partial deletions. Duplications of DAZ gene copy have also been observed in this study.
Conclusions: To date, these observations are the first evidences showing that partial AZFc deletions can increase the risk of complete AZFc deletion. The susceptibility of partial AZFc deletions to complete AZFc deletion deserves further examination, especially in the populations or Y haplogroups abundant in partial AZFc deletions.
- AZFc deletion
- Y chromosome
- male infertility
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