A Drosophila clathrin light-chain gene: sequence, mapping, and absence of neuronal specialization

Because mammalian light chains have been implicated in the regulation of clathrin coat assembly and neuronal specialization of clathrin-mediated vesicle trafficking, a clathrin light-chain gene of Drosophila has been sought as a genetically tractable model for these developmental membrane-trafficking systems. A light-chain gene has been identified and its expression examined in various developmental stages and tissues by reverse transcriptase-polymerase chain reaction (RT-PCR). A cDNA clone, originally identified from a partial sequence in the Berkeley Drosophila Genome Project EST database, has been sequenced completely and shown to encode a polypeptide with extensive sequence similarity to vertebrate and invertebrate clathrin light chains. Secondary structure algorithms predict an extensive coiled-coil over a region extending from amino acid residues 100 to 170, in excellent agreement with previous analyses of mammalian light chains. By in situ hybridization to larval polytene chromosomes, the gene has been mapped to cytologic position 77A on the left arm of chromosome 3. An RT-PCR analysis, coupled with PCR analysis of genomic DNA, showed that there is no neural specialization of the Drosophila clathrin light chain corresponding to that observed in mammalian neuronal light chains. The neuron-specific alternative splicing of clathrin light chains thus appears to be restricted to vertebrates, where it may contribute to the more complex information-processing capacity of higher nervous systems.