RESUMEN
Dapper was isolated in a screen for proteins interacting with Dishevelled, a key factor in Wnt signaling. Dapper and Dishevelled colocalize intracellularly and form a complex with Axin, GSK-3, CKI, and beta-catenin. Overexpression of Dapper increases Axin and GSK-3 in this complex, resulting in decreased soluble beta-catenin and decreased activation of beta-catenin-responsive genes. Dapper also inhibits activation by Dishevelled of c-Jun N-terminal kinase (JNK), a component of beta-catenin-independent Frizzled signaling. Inhibition of Dapper activates both beta-catenin-responsive genes and an AP1-responsive promoter, demonstrating that Dapper is a general Dishevelled antagonist. Depletion of maternal Dapper RNA from Xenopus embryos results in loss of notochord and head structures, demonstrating that Dapper is required for normal vertebrate development.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Proteínas del Citoesqueleto/metabolismo , Proteínas Quinasas JNK Activadas por Mitógenos , Quinasas de Proteína Quinasa Activadas por Mitógenos/metabolismo , Notocorda/embriología , Proteínas Nucleares , Fosfoproteínas/metabolismo , Proteínas Represoras , Transactivadores , Proteínas de Xenopus/genética , Proteínas de Xenopus/metabolismo , Proteínas de Pez Cebra , Animales , Proteína Axina , Proteínas Quinasas Dependientes de Calcio-Calmodulina/metabolismo , Proteínas Portadoras/química , Caseína Quinasas , Secuencia Conservada , Proteínas del Citoesqueleto/antagonistas & inhibidores , Proteínas Dishevelled , Eliminación de Gen , Regulación del Desarrollo de la Expresión Génica , Glucógeno Sintasa Quinasa 3 , Células HeLa , Humanos , Enlace de Hidrógeno , Técnicas In Vitro , MAP Quinasa Quinasa 4 , Datos de Secuencia Molecular , Notocorda/metabolismo , Fenotipo , Unión Proteica/fisiología , Proteínas Quinasas/metabolismo , Estructura Terciaria de Proteína , Proteínas/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Homología de Secuencia de Aminoácido , Vertebrados , Proteínas Wnt , Proteínas de Xenopus/química , Xenopus laevis , beta CateninaRESUMEN
Transgene insertions in the mouse often cause mutations at chromosomal loci. Analysis of insertion mutations that cause male sterility may lead to the identification of novel molecular mechanisms implicated in male fertility. Here we show a line of transgenic mice with dominant inheritance of male sterility (DMS) that was found amid several lines that were normally fertile. Transgene-positive males from this line invariably were sterile, whereas transgenic females and transgene-negative male littermates were fertile. Histologic analysis and TUNEL staining for apoptotic cells in DMS testis showed spermatogenesis arrest at metaphase of meiosis I (M-I), accompanied by massive apoptosis of spermatocytes. Meiosis I arrest was incomplete, however, as small numbers of spermatids and spermatozoa were found. Both round spermatids and spermatozoa were evaluated for their permissiveness in the assisted reproductive technologies intracytoplasmic sperm injection (ICSI) and round spermatid injection (ROSI). Surprisingly, ROSI but not ICSI gave live offspring, suggesting that mature sperm had deteriorated by the time of recovery from the epididymis. Mapping the transgene insertion by fluorescence in situ hybridization revealed a site on chromosome 14 D3-E1. Two candidate genes, GFR alpha 2 and GnRH, that were previously mapped to that region and the functions of which in spermatogenesis are well established were not altered in DMS. As a consequence, positional cloning of the DMS locus will be essential to identify new molecules potentially involved in arrest at M-I. Furthermore, mice carrying this genetic trait might be useful for studies of assisted reproductive technologies and male contraceptives.