All ETDs from UAB

Advisory Committee Chair

Guillermo Marques

Advisory Committee Members

Anne C Woods

Chenbei Chang

Michael A Miller

Scott M Wilson

Document Type

Dissertation

Date of Award

2010

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

During nervous system development, neurons proliferate, differentiate, project their axons to their targets and make synapses with them. At the neuromuscular junction of Drosophila, these functional synapses enlarge as the body grows to maintain physiologically effective synaptic transmission with the muscles. Drosophila Bone Morphogenetic Protein (BMP) type II receptor, Wishful thinking (Wit), is important in this proper synaptic growth and function. To identify transcriptional targets of Wit signaling, we performed microarray experiments comparing normal controls to wit mutants. Through this study, we found that some of the verified target genes showed isoform-specific regulation in wit mutants, and that several neuropeptide hormones were down-regulated in wit mutants. One of the most promising targets is the novel gene CG9335 that shows 2.35 fold decrease in microarrays and about 3 fold decrease by Quantitative Real time PCR (QRT-PCR) in mutants. In situ hybridization results show that CG9335 is expressed in the optic lobe proliferating center, ventral ganglion of larval CNS and eye imaginal discs. CG9335 expression is specifically eliminated in the ventral ganglion of wit mutants. Molecular characterization of CG9335 shows that it is a Ly-6 domain-containing, GPI-anchored cell surface protein. Co-expression studies by in situ hybridization strongly suggest that CG9335 is a motoneuron expressed gene. Functional characterization using a null allele revealed that CG9335 mutants have defects in spontaneous synaptic vesicle release. The significantly decreased frequency of spontaneous vesicle release of CG9335 mutants can be rescued by neuronal expression of a CG9335 transgene. Wit mutants also show a decreased frequency of spontaneous synaptic vesicle release, and the phenoptype can be partially rescued by presynaptic expression of CG9335. Through our study, we proved our tested hypothesis; the canonical BMP signaling pathway regulates downstream target genes that are important for synaptic development and function. Further validation and study of other targets identified in our microarray study will provide much more valuable information about how BMP signaling orchestrates synapse formation and function.

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