Y chromosome microdeletions and alterations of spermatogenesis

Three different spermatogenesis loci have been mapped on the Y chromosome a nd named "azoospermia factors" (AZFa, b, and c). Deletions in these regions remove one or more of the candidate genes (DAZ, RBMY, USP9Y, and DBY) and cause severe testiculopathy leading to male infertility. We have reviewed t he literature and the most recent advances in Y chromosome mapping, focusin g our attention on the correlation between Y chromosome microdeletions and alterations of spermatogenesis. More than 4,800 infertile patients were scr eened for Y microdeletions and published. Such deletions determine azoosper mia more frequently than severe oligozoospermia and involve especially the AZFc region including the DAZ gene family. Overall, the prevalence of Y chr omosome microdeletions is 4% in oligozoospermic patients, 14% in idiopathic severely oligozoospermic men, 11% in azoospermic men, and 18% in idiopathi c azoospermic subjects. Patient selection criteria appear to substantially influence the prevalence of microdeletions. No clear correlation exists bet ween the size and localization of the deletions and the testicular phenotyp e. However, it is clear that larger deletions are associated with the most severe testicular damage. Patients with Y chromosome deletions frequently h ave sperm either in the ejaculate or within the testis and are therefore su itable candidates for assisted reproduction techniques. This possibility ra ises a number of medical and ethical concerns, since the use of spermatozoa carrying Y chromosome deletions may produce pregnancies, but in such cases the genetic anomaly will invariably be passed on to male offspring.