PhD Transfer Exam – Ishrat Maliha Islam (Erclik labs)

PhD Transfer Exam

Thursday, June 8, 2017 at 1:10 pm, CCT-3150, University of Toronto at Mississauga

Ishrat Maliha Islam (Erclik labs)

“ Selective integration of spatial inputs during Drosophila optic lobe neurogenesis”

Abstract

The Drosophila optic lobe serves as an excellent model system in which to study the mechanisms that regulate neurogenesis. The largest neuropil of the optic lobe, the medulla, is comprised of 40 000 neurons belonging to over 70 neuronal types. These neurons are generated from a single layered epithelial crescent called the outer proliferation center (OPC). Recently, it has been shown that OPC neuroblasts (NB) generate unique sets of neurons based on their temporal state and spatial origin. Surprisingly, NBs that receive identical spatial and temporal inputs can generate both spatially refractory and spatially sensitive neural progeny; uni-columnar neurons are generated by all NBs regardless of spatial origin whereas multi-columnar neurons are generated in spatially restricted domains. For example, despite receiving identical spatial and temporal cues, the two NBs born at the intersection of the Vsx1 spatial and Homothorax (Hth) temporal windows generate distinct neuronal progenies; Pm3s are spatially sensitive multi-columnar neurons while Mi1s are spatially insensitive uni-columnar neurons. This selective integration of spatial inputs during neurogenesis likely serves to control the position and number of neurons that are generated. In this thesis, I propose to address the genetic and molecular mechanisms underlying selective integration within medulla NBs. To date, I have identified that the transcription factor Klumpfuss differentially labels the second Hth NB (but not the first), suggesting that selective integration may occur at the level of the NB itself. I have also found that the transcription factors Rx and Runt are expressed differentially in the Hth1 and Hth2 NB lineages, respectively. During my PhD, I will take advantage of the sophisticated genetic tools available in Drosophila to analyze the lineage relationship of Pm3 and Mi1 neurons. I also propose to utilize transcriptomics and candidate gene approaches to uncover the genetic mechanisms underlying selective integration. Finally, I will characterize the role of Rx and Runt in Hth⁺ NB lineages. It is anticipated that this research will contribute to our understanding of neurogenesis in both flies and vertebrates where multipotent stem cells also possess the ability to incorporate specific developmental cues to regulate neuronal properties.