Species: mouse
Mutation name: None
type: null mutation
fertility: fertile
Comment: Meiosis I Arrest Abnormalities Lead to Severe Oligozoospermia in Meiosis 1 Arresting Protein (M1ap)-Deficient Mice. Arango NA et al. Meiosis 1 arresting protein (M1ap) is a novel vertebrate gene expressed exclusively in germ cells of the embryonic ovary and the adult testis. In male mice, M1ap expression, which is present from spermatogonia to secondary spermatocytes, is evolutionarily conserved and has a specific spatial and temporal pattern suggestive of a role during germ cell development. To test its function mice deficient in M1ap were created. While females had histologically normal ovaries, males exhibited reduced testicular size and a myriad of tubular defects, which led to severe oligozoospermia and infertility. Albeit some germ cells arrested at the zygotene/pachytene stages, most cells advanced to metaphase I before arresting and entering apoptosis. Cells that reached metaphase I were unable to properly align their chromosomes at the metaphase plate due to abnormal chromosomes synapses and failure to form crossover foci. Depending on the state of tubular degeneration, all germ cells, with the exemption of spermatogonia, disappeared; with further deterioration, tubules displaying only Sertoli cells reminiscent of Sertoli cell only syndrome in humans were observed. Our results uncovered an essential role for M1ap as a novel germ cell gene not previously implicated in male germ cell development, and suggest that mutations in M1AP could account for some cases of non-obstructive oligozoospermia in men.