Búsqueda y análisis de genes candidatos a regular la expresión génica en respuesta a la ruta de señalización EGRF/RAS en el ala de Drosophila Melanogaster

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología Molecular. Fecha de lectura: 16-06-2008The development of the Drosophila melanogaster wing is a model system to analyse the genetic control of organ size, shape and pattern. Many known genes participate in a variety of processes, including cell survival, growth, proliferation and differentiation, which govern the generation of the adult wing. In this work we pursuit two main objectives, to identify new genes participating in wing development and to analyse the contribution of chromatin remodelling in the regulation of gene expression in response to EGFR signalling. In the first part we discuss the generation, mapping and functional analysis of new mutations induced in the 2L chromosomic arm which in homozygosis result in a wing phenotype affecting its size, margin and the pattern of veins. We have obtained 12 complementation groups corresponding to genes with a proven role in wing development such as smoothened, thick veins, Mothers against dpp, expanded and fat, and 73 new complementation groups represented by at least one allele. We studied in more detail a novel complementation group corresponding to the gene med15, a Mediator Complex member, and aimed to elucidate the role of Med15 in the network of gene expression regulation controlling the development of the veins. In the second part we analyse the functional requirements of Osa, a component of the SWI/SNF chromatin-remodelling complex, during Drosophila wing development. We found that osa is needed for imaginal cells growth and survival, and for the correct patterning of sensory organs and veins. Genetic interactions between osa alleles and mutations affecting the activity of the EGFR pathway suggest that one key aspect of Osa is intimately related to the response to EGFR activity. Thus, loss of osa and EGFR signalling result in similar wing vein phenotypes, and Osa is required for the expression of several nuclear targets of EGFR signalling, such as Delta, rhomboid and argos. We suggest that Osa facilitates the transcriptional responses to EGFR signalling in the wing, likely after EGFR-specific transcription factors are attached to their promoters, making the regulatory regions of EGFR target genes stably activated. The function of Osa is also shared by other members of the BAP complex, such as Snr1, Bap55, Mor and Brm, indicating that chromatin remodelling is a key component of transcriptional regulation in response to EGFR signalling