Análisis de los genes y mecanismos que median las funciones de las proteínas Spalt en el ala de Drosophilamelanogaster

Abstract

Analisis de los genes y mecanismos que median las funciones de las proteinas Spalt en el ala de Drodophila melanogaster. The Drosophila spalt genes (spalt-major and spalt-related) encode conserved Zn-fingers transcription factors which expression is activated by the Dpp/BMP signalling pathway in the wing disc. They are required for cell survival, cell cycle progression, epithelial integrity and vein pattern formation, and mediate most of the Dpp/BMP functions during wing development. The identification of Spalt target genes and the analysis of their functions are critical steps toward understanding the genetic control of wing disc development by BMP/Dpp signalling. In this thesis we identified using microarray experiments a considerable change in the transcriptional landscape of the imaginal wing disc in response to the loss of spalt expression. We also study the in situ expression of those genes which expression varied significantly as a consequence of spalt loss of function. These approaches led us to identify a group of candidate Spalt targets that include positively and negatively regulated genes. To address the contribution of each of these genes to the Spalt function, we analysed the wing phenotypes caused by the reduction of their expression, and we were able to find a group of potential mediators of Sal activity. We focussed our analysis on a candidate, optix, examining its role in the patterning of the L2 vein; we identifed a novel mechanism linking Spalt function with the regulation of the L2- determining gene knirps. We also analysed the relationship between JNK pathway activation and BMP/Dpp activity in the wing disc, describing a novel link between these two pathways through which BMP/Dpp activates JNK signalling and Spalt represses this activation by regulating the expression of the JNK pathway ligand eiger. Finally, we also addressed the mechanisms involved in the regulation of gene expression by Spalt proteins. We identified 9 DNA regions that drive reporter gene expression in response to Spalt, and describe an A/T-rich sequence enriched in these fragments. In this context, we identified the proteins Caf1-55, Sap130 and MEP-1 as critical components of the transcriptional repression mechanism mediated by Spalt-m.