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Title: A screen for genes regulating neuroblast activity in Drosophila
Author: Pendred, Julia
ISNI:       0000 0001 3482 7354
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 2008
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Following embryogenesis, the morphology of the CNS becomes dramatically remodelled to reflect the different locomotive and sensory requirements of the adult relative to the larva. This is largely achieved through the varying spatio-temporal proliferation patterns of the neural stem cell-like precursors (termed postembryonic neuroblasts: pNBs). Although both NB-autonomous and non-cell autonomous mechanisms have been identified, relatively few factors controlling this process are known. My studies focus on using genetic screening to identify new genes involved in this process. I executed two genetic screens, which were designed to complement each others limitations. The first of these involved screening using Mosaic Analysis with a Repressible Cell Marker (MARCM), to identify embryonic-lethal mutations that act in a cell-autonomous manner to produce under- or over-sized pNB clones. The second screen focused on the rarer class of pupal-lethal mutation, where homozygous mutant larvae were screened for abnormal morphology of the CNS. In total, we screened 4200 mutagenised lines on chromosome III, recovering 82 mutants with interesting phenotypes 68 from the MARCM screen and 14 from the pupal-lethal screen. These were divided into 69 complementation groups, 9 of which contained multiple alleles. These groups were subdivided into phenotypic classes, with 9 distinct classes recovered from the MARCM screen and 2 from the pupal-lethal screen. These were sub-categorised into CNS-specific or non-CNS specific, according to the absence or presence of a phenotype in the eye disc. I initially focused my studies on 9 of the pupal-lethal mutations, 5 of which I successfully mapped using chromosomal deficiencies, to 38-329Kb intervals. Two mutations showing undersized brain lobes, juvenile at mid-third instar (jami) and reduced optic and imaginal expansion (roie) were selected for detailed molecular and genetic analysis and comparison. Both genes are required in differing region- and stage-specific manners throughout the CNS. jami positively regulates CNS growth by both non-cell autonomous and cell-autonomous mechanisms, according to the region and stage. In contrast roie promotes growth in a strictly cell-autonomous manner with a strong requirement in symmetrically dividing precursors. Using deficiencies, jami was fine-mapped to a region containing 5 genes and one strong candidate gene for roie, CGI3074, was identified by P-element mediated recombination mapping combined with genetic techniques and available Drosophila database resources.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available