A GENETIC SCREEN FOR SECOND CHROMOSOME MODIFIERS OF A TEMPERATURE-SENSITIVE PRESYNAPTIC CALCIUM CHANNEL MUTANT OF DROSOPHILA

Open Access
Author:
Acharjee, Shaona
Graduate Program:
Biology
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
March 07, 2008
Committee Members:
  • Richard W Ordway, Committee Chair
  • Kyuang Han, Committee Member
  • Zhi Chun Lai, Committee Member
  • Wendy Hanna Rose, Committee Member
Keywords:
  • Drosophila
  • neurotransmission
  • cac
  • temperature- sensitive
  • paralysis
  • calcium channel
Abstract:
Synaptic release of chemical neurotransmitters is triggered by calcium influx through presynaptic voltage-gated calcium channels. In Drosophila, the molecular basis of presynaptic calcium channel function has been defined through analysis of cacTS2, a temperature-sensitive (TS) paralytic mutant of the calcium channel α1 subunit gene, cacophony. The cacTS2 mutant has also served as a starting point for further genetic analysis. To broaden our understanding of the functions and interactions of cac-encoded calcium channels, we conducted a screen for second chromosome genetic modifiers of the cacTS2 paralytic phenotype. Two mutations have been recovered as enhancers of cacTS2. Electrophysiological analysis indicates these mutations affect synaptic transmission. Both the mutations are alleles of the same gene. Meiotic and deficiency mapping has placed both the mutations in the right arm of the second chromosome within the cytological region 54D4-54D5. Molecular characterization is expected to identify the mutation locus and further define the in vivo roles of the gene products in this process. The work presented in this thesis outlines the background of the project in the first chapter. Molecular mechanisms of signal transmission at chemical synapses, the role of voltage gated calcium channels at the presynaptic terminals and the utility of TS mutants in studying the synaptic transmission have been discussed. The genetic screen for second chromosome modifiers of cacTS2 TS paralytic phenotype followed by phenotypic and genotypic characterization of the modifiers obtained from the screen has been described in the second and third chapter. These results have been discussed in referencd to the current understanding of the synaptic transmission. The mutants recovered in this screen are either novel TS alleles of previously characterized genes or may identify new members of the molecular machinery governing the synaptic transmission.