Absence of testicular DAZ gene expression in idiopathic severe testiculopathies

Deletions of the DAZ (deleted in azoospermia) gene family are frequently re sponsible for male infertility and are generally assessed by analyses of ge nomic DNA extracted from peripheral leukocytes. The multicopy nature of thi s gene prevents the distinction of intragenic deletions or deletions not in volving the whole DAZ gene cluster. Thus it is still unclear whether each D AZ copy is effectively expressed in the testis. We analysed, by reverse tra nscription-polymerase chain reaction (RT-PCR), the expression of DAZ, RBM a nd SRY genes, in testicular cells from infertile men affected by idiopathic severe hypospermatogenesis, obstructive azoospermia and Sertoli cell-only syndrome. Normal mRNA for DAZ, RBM and SRP were observed in obstructive azo ospermia, whereas only SRP transcripts were detected when only Sertoli cell s were present. Nine out of 10 patients affected by idiopathic severe hypos permatogenesis had normal expression of SRY, RBM and DAZ, while in one pati ent no DAZ transcript was detected, suggesting that his testiculopathy was related to the absence of DAZ expression. The lack of DAZ mRNA in testicula r cells with an apparently normal DAZ gene constitution on DNA extracted fr om leukocytes may be explained by different hypotheses: (i) not all the cop ies of the DAZ gene cluster are transcribed in the germ cells and the repor ted patient had a small deletion involving only the active ones; (ii) the p atient may be mosaic for the DAZ gene having a normal constitution in leuko cytes and be deleted for DAZ gene in the testis; (iii) abnormalities of DAZ transcription may er;ist. These findings highlight the intrinsic interpret ative difficulties of normal PCR analysis for DAZ and RBM on leukocytes and suggest caution in the use of germ cells for assisted reproductive techniq ues in these cases to avoid transmission of genetic abnormalities to male o ffspring.