RESUMEN
We have screened chromosome arm 3L for ethyl methanesulfonate-induced mutations that disrupt localization of fluorescently labeled gurken (grk) messenger (m)RNA, whose transport along microtubules establishes both major body axes of the developing Drosophila oocyte. Rapid identification of causative mutations by single-nucleotide polymorphism recombinational mapping and whole-genomic sequencing allowed us to define nine complementation groups affecting grk mRNA localization and other aspects of oogenesis, including alleles of elg1, scaf6, quemao, nudE, Tsc2/gigas, rasp, and Chd5/Wrb, and several null alleles of the armitage Piwi-pathway gene. Analysis of a newly induced kinesin light chain allele shows that kinesin motor activity is required for both efficient grk mRNA localization and oocyte centrosome integrity. We also show that initiation of the dorsoanterior localization of grk mRNA precedes centrosome localization, suggesting that microtubule self-organization contributes to breaking axial symmetry to generate a unique dorsoventral axis.
Asunto(s)
Centrosoma/metabolismo , Proteínas de Drosophila/genética , Drosophila/metabolismo , ARN/metabolismo , Factor de Crecimiento Transformador alfa/genética , Animales , Mapeo Cromosómico , Drosophila/crecimiento & desarrollo , Proteínas de Drosophila/antagonistas & inhibidores , Proteínas de Drosophila/metabolismo , Femenino , Pruebas Genéticas , Secuenciación de Nucleótidos de Alto Rendimiento , Cinesinas/genética , Cinesinas/metabolismo , Masculino , Oocitos/metabolismo , Oogénesis , Polimorfismo de Nucleótido Simple , ARN/química , ARN Mensajero/análisis , ARN Mensajero/metabolismo , ARN Interferente Pequeño/metabolismo , Análisis de Secuencia de ADN , Factor de Crecimiento Transformador alfa/metabolismoRESUMEN
Integrins act at signalling crossroads, and their interactions with other signal transduction pathways are key to the regulation of normal and pathological cell cytoarchitecture and behaviour. Here, we describe a signalling cascade that acts during the formation of the defining segmental features of the vertebrate body - the somites - in which ß1-integrin activity regulates epithelialisation by controlling downstream Wnt and Notch activity crucial for somite border formation. Using in vivo transcriptional inhibition in the developing chick embryo, we show that ß1-integrin in the anterior presomitic mesoderm activates canonical Wnt signalling in a cell-autonomous, `outside-inside' manner. Signalling is mediated by integrin-linked kinase (ILK), leading to modulation of glycogen synthase kinase 3ß (GSK3ß) phosphorylation, and activates Notch signalling in the anterior presomitic mesoderm. The two signalling pathways then cooperate to promote somite formation via cMESO1/Mesp2. Our results show that ß1-integrin can regulate cell shape and tissue morphogenesis indirectly, by regulation of downstream signalling cascades.
