Expression profile of Caenorhabditis elegans cadherins and their functions in worm development.

摘要

Cadherins are Ca++ -dependent cell adhesion proteins mediating general adhesion between cells and at specialized sites. They are implicated in many aspects of animal development involving selective cell adhesion. They regulate cell growth and survival, cell migration and are structural components of synapses as well as candidate instructive factors for synapse patterning.; Few of the twelve cadherin genes in C. elegans have been functionally characterized. Their roles during worm development, especially nervous system development are largely unknown. Of commonly used gene reporters, GFP-tagged transcriptional constructs can serve as a quick and fairly reliable tool to represent gene expression patterns thus help predict possible functions. In the twelve worm cadherin genes, ten are expressed in the nervous system, most with a restricted pattern. Ten genes show epithelial expression. Most cadherin genes are also observed in the intestine. Four genes are observed in the excretory system. Seven genes have expression in muscle cells with a highly restricted patterns. All of the neuronally expressed cadherins present in neuronal pairs that form synapses, suggesting a possible role of cadherins during axon migration and/or synapse specification.; Mutants except that of cdh-10 and cdh-12 were available at the time when this thesis was written. Behaviors including locomotion, mechanosensation, pharyngeal pumping, defecation were examined and several of them showed defects.; Phasmid axon morphology of the cadherin mutants were examined and some defects were observed, suggesting some cadherins have functions in axon extension.; Calsyntenin/Alcadein is a highly conserved novel membrane protein with two extracellular EC-like repeats and one laminin G module and a highly acidic cytoplasmic domain that binds Ca++ in vitro. In the worm, this gene is expressed in most/all of the neurons as well as other tissues. CASY-1 protein is localized in neuronal cell membrane, abundant at newly formed synapses, cleaved and its ectodomain is transported into vesicular compartments of coelomocytes while the cytodomain is internalized. casy-1 mutants behaved normally in most tests including locomotion, mechanosensation, dauer formation/recovery, mating, brood size, etc; while showed learning defects after certain conditioning in salt avoidance, temperature avoidance and olfactory adaptation.