A novel approach for the analysis of DAZ gene copy number in severely idiopathic infertile men

The deleted-in-azoospermia (DAZ) gene family constitutes the major candidate for the AZFc (azoospermia factor c) phenotype of male infertility, being deleted in about 10% of azoospermic and severely oligozoospermic subjects. Four DAZ genes are arranged in two clusters in AZFc, and standard analysis by PCR cannot distinguish among the different copies. Therefore only deletions of the entire gene cluster can be identified. We developed a PCR amplification-restriction digestion assay able to distinguish from DAZ genes for single nucleotide variants. Then we applied this approach to screen a group of idiopathic infertile men in which the DAZ genes presence was previously assessed by standard PCR analysis. Two patients out of 25 showed deletion of two copies of DAZ (DAZI and 2), suggesting that this mutation was actually the cause of spermatogenic damage. This preliminary screening demonstrates that deletions of copies of DAZ genes may be often found in severely infertile men and it strengthens the role of this gene family in spermatogenesis. Furthermore, this simple method, being able to distinguish among the different DAZ copies, could be used to screen a larger number of patients and to perform a more accurate diagnosis.