Molecular genetic analysis of smellblind mutants in Drosophila

Date of Completion

January 2004


Biology, Molecular|Biology, Neuroscience|Biology, Genetics




The smellblind (sbl) mutations were originally identified in screens for mutants defective in larval chemosensation or adult olfactory-based learning. Subsequently, sbl mutations were shown to be alleles of the para locus, the structural gene for the action potential Na+ channel. The parasbl alleles are unique, in that, most para mutations are hypomorphic and confer recessive temperature-sensitive (ts) paralysis with no olfactory defects. Likewise, parasbl mutants are not ts-paralytic. Here I show that the sbl alleles of para are defective in the production of a particular rare alternative splice-form of the Na+ channel. The molecular lesions in all isolated sbl alleles were found to be consistent with this splicing defect. The rare alternative splice occurs in a functionally important region of the Na+ channel protein and is located in an ancient and highly conserved portion of the ion channel. Moreover, the same alternative splicing event is also conserved between invertebrate and vertebrate sodium channel genes. In addition, the rare alternative splice is developmentally and spatially regulated. The possible cell-specific regulation of this alternative splicing within the nervous system was shown via transgenic alternative-splicing fluorescent reporter constructs. Lastly, RNA binding factor, pasilla, was identified as a key splicing factor in the regulation of this rare alternative splicing event in para. ^