|M.Sc Student||Hassan Abeer|
|Subject||An RNAi-Based Genetic Screen Identifies New Genes|
Required for Normal Morphogenesis of
Proprioceptors in Drosophila
|Department||Department of Medicine||Supervisor||Professor Adi Salzberg|
|Full Thesis text|
One of the major goals of developmental biology is to understand how cells establish their unique morphologies to create an organ with a proper cell-cell interaction and function. To answer this question and gain insight into morphological processes required for the establishment of functional multicellular organ, we used the proprioceptive chordotonal organs (ChOs) of Drosophila as a model system. ChOs are internal sensory organs composed of six different cell types, they develop during embryogenesis and start to function upon initiation of larval movement. During larval stages the ChOs go through major morphological changes which are required for their proper functionality
Here we describe an RNAi-based genetic screen for novel determinants of ChO development. To allow easy screening in 2nd instar larvae we constructed transgenic fly strain which contain the relevant Gal4 in the background of novel fluorescent markers that label different cells in the ChO lineage. These strains were used for screening more than 1000 an RNAi strains directed against 500 candidate genes. 27 genes were identified in the screen as required for normal ChO morphogenesis.
Each of the ChO cell types is characterized by the expression of a unique set of genes that contribute to its specialized structure and function. Some of these genes encode for variants of α and β tubulin, two basic subunits constructing the microtubules (MT). The Drosophila genome encodes for four α-tubulin variants and four β-tubulin variants. In the ChOs, α-tubulin-85E and β1-tubulin are expressed specifically in the accessory and attachment cells, whereas β3-tubulin expression is restricted to cap cells. The RNAi screen revealed that reducing the levels of each tubulin isoform within all cells of ChO leads to different phonotypic effects. The distribution of the different tubulin isoforms within the ChOs together with the abnormal phenotypes caused by their loss of function can help us to link between the structure of the microtubules and specific cellular properties.