RESUMO
Tumor suppressor of lung cancer 1 (TSLC1), also known as SgIGSF, IGSF4, and SynCAM, is strongly expressed in spermatogenic cells undergoing the early and late phases of spermatogenesis (spermatogonia to zygotene spermatocytes and elongating spermatids to spermiation). Using embryonic stem cell technology to generate a null mutation of Tslc1 in mice, we found that Tslc1 null male mice were infertile. Tslc1 null adult testes showed that spermatogenesis had arrested at the spermatid stage, with degenerating and apoptotic spermatids sloughing off into the lumen. In adult mice, Tslc1 null round spermatids showed evidence of normal differentiation (an acrosomal cap and F-actin polarization indistinguishable from that of wild-type spermatids); however, the surviving spermatozoa were immature, malformed, found at very low levels in the epididymis, and rarely motile. Analysis of the first wave of spermatogenesis in Tslc1 null mice showed a delay in maturation by day 22 and degeneration of round spermatids by day 28. Expression profiling of the testes revealed that Tslc1 null mice showed increases in the expression levels of genes involved in apoptosis, adhesion, and the cytoskeleton. Taken together, these data show that Tslc1 is essential for normal spermatogenesis in mice.
Assuntos
Imunoglobulinas/fisiologia , Infertilidade Masculina/genética , Proteínas de Membrana/fisiologia , Espermátides/crescimento & desenvolvimento , Espermatogênese/genética , Espermatozoides/anormalidades , Proteínas Supressoras de Tumor/fisiologia , Animais , Apoptose , Adesão Celular/genética , Molécula 1 de Adesão Celular , Moléculas de Adesão Celular , Diferenciação Celular , Citoesqueleto/genética , Embrião de Mamíferos/citologia , Epididimo/química , Epididimo/citologia , Expressão Gênica , Imunoglobulinas/análise , Imunoglobulinas/genética , Infertilidade Masculina/metabolismo , Masculino , Proteínas de Membrana/análise , Proteínas de Membrana/genética , Camundongos , Camundongos Mutantes , Mutação , Análise de Sequência com Séries de Oligonucleotídeos , Motilidade dos Espermatozoides/genética , Espermátides/citologia , Espermátides/metabolismo , Espermatozoides/citologia , Espermatozoides/metabolismo , Células-Tronco/metabolismo , Testículo/química , Testículo/citologia , Proteínas Supressoras de Tumor/análise , Proteínas Supressoras de Tumor/genética , Regulação para CimaRESUMO
Testicular apoptosis is involved in the regulation of germ cell numbers, allowing optimal sperm production. Apoptosis has been described to occur in response to the absence of hormonal stimulation of the testis. Here we investigate the effect of the physiological lack of gonadotropins from birth using the hypogonadal (homozygous for the mutant allele Gnrh1(hpg)) mouse as a model. We pursued a concerted strategy using microarray analysis and RT-PCR to assess transcript levels, TUNEL to quantify the incidence of apoptosis, and Western blotting to assess the respective contribution of the extrinsic and intrinsic apoptotic pathways. Our results indicate a large increase in apoptosis of both somatic and germ cell compartments in the hpg testis, affecting Sertoli cells as well as germ cells of all ages. We confirmed our observations of Sertoli cell apoptosis using anti-Mullerian inhibiting substance staining and staining for cleaved fodrin alpha. In the somatic compartment, apoptosis is primarily regulated via the membrane receptor (extrinsic) apoptotic pathway, while in the germ cell compartment, regulation occurs via both the mitochondrial (intrinsic) and membrane receptor (extrinsic) apoptotic pathways, the latter potentially in a stage-specific manner. This study is the first report of spermatogonial apoptosis in response to gonadotropin deficiency as well as the first report of Sertoli cell apoptosis in response to gonadotropin deficiency in the mouse.