Identificación de nuevos genes implicados en la formación de las venas del ala de drosophila melanogaster y caracterización funcional de Moesin, laminina B1 y CG9056

Abstract

The formation of veins in the Drosophila wing requires the activity of the Notch, EGFR and Dpp signalling pathways. To identify novel elements belonging to these pathways, we carried out an over-expression screen, selecting among 13.000 novel P-UAS insertions those that modify vein formation in combination with a vein-specific Ga14 driver. We selected and mapped 500 P-UAS insertions, identifying approximately 300 genes that when over-expressed in the pupal veins affect vein formation, cell differentiation or wing morphology. We found in the screen 70% of the known members of the Notch, EGFR and Dpp pathways.

In this work I present the results of the mutagenesis screen and the analysis of three lines of interest affecting the genes Moesin, LanB1 and CG9056. Moesin belongs to the ERM family, a group of cytoplasmic proteins linking the sub-cortical actin cytoskeleton to specific transmembrane proteins. We generated a novel moe loss of function allele (moec858) and studied its phenotypes in the adult wing, finding two main developmental abnormalities: 1) reduced wing size, abnormal hinge and vesicles of wing tissue differentiating trapped between the dorsal and ventral wing surfaces, and 2) alterations in the pattern of the L3 vein. The analysis of the corresponding imaginal discs reveals profound alterations in wing imaginal disc morphology, as well as changes in the expression of several targets of the Hedgehog signalling pathway. The activity of other signalling pathways such as Notch, Dpp, Wg and EGFR is not modified in moec858wing discs. We suggest that Moe has a novel requirement in Hh signalling that is independent of its function during epithelial morphogenesis.

The second gene analysed codifies one of the three subunits of Laminin: LanB1. Laminin is a component of basal membranes. The over-expression of LanB1 causes defects in the vein pattern similar to those observed when the activity of Notch signalling is reduced. We characterize the gain-of-function phenotype of LanB 1 and induced two loss-of-function alleles in the gene. Loss of LanB1 affects the adhesion between the dorsal and ventral wing surfaces. Finally, we analysed the gene CG9056, which over-expression causes loss of vein differentiation. We analysed the loss of CG9056 function, finding that the gene is required to prevent vein formation by antagonizing the EGFR and/or Dpp signalling pathways.