What are the germ cell phenotypes from infertile men telling us about spermatogenesis?

Abstract

Drosophila mutants for known genes and those obtained following germline genetic engineering in mice have led to the identification of genes involved in the initiation and the maintenance of spermatogenesis and in the different steps of meiosis. Mutants allow the definition of meiosis-specific checkpoint controls that ensure the transmission of complete and undamaged genetic information. They reveal what spermatogenesis events are interdependent. In the light of these data, an attempt is made to define which events of spermatogenesis could be defective in some well-defined human spermatogenesis failures. They appear to be good models to study the decouplages of spermatogenesis events, the morphogenetic relationships between germ cell structures and the occurrence of pleiotropic sperm phenotypes. It is discussed whether a germ cell with a normal phenotype can transmit a non-functional gene involved in spermatogenesis and how homologous genes can lead to different germ cell phenotypes depending on the species.