Dominant Cold-Sensitive Out-Cold Mutants of Drosophila melanogaster Have Novel Missense Mutations in the Voltage-Gated Sodium Channel Gene paralytic

• Published in: Genetics (Austin) Vol. 180; no. 2; pp. 873 - 884
• Main Authors: Lindsay, Helen A, Baines, Richard, ffrench-Constant, Richard, Lilley, Kathryn, Jacobs, Howard T, O'Dell, Kevin M.C
• Format: Journal Article
• Language: English
• Published: United States Genetics Soc America 01.10.2008; Genetics Society of America
• Subjects: Alleles; Amino Acid Sequence; Animals; cold; dominant genes; Drosophila melanogaster; Drosophila melanogaster - genetics; Drosophila melanogaster - physiology; Drosophila Proteins - genetics; Drosophila Proteins - metabolism; Genes; Genes, Insect; Genetic disorders; Genetics; Genotype & phenotype; Investigations; Males; Mass spectrometry; missense mutation; Mitochondrial Proteins - genetics; Mitochondrial Proteins - metabolism; Models, Biological; Molecular Sequence Data; mutants; Mutation; Mutation, Missense; Ocd gene; Out-cold mutants; para gene; Paralyses, Familial Periodic - genetics; Paralyses, Familial Periodic - metabolism; paralysis; Phenotype; Proteins; Reaction kinetics; sodium channels; Sodium Channels - genetics; Sodium Channels - metabolism; Studies; Thermosensing - genetics
• DOI: 10.1534/genetics.108.090951
• ISSN: 0016-6731; 1943-2631

Here we report the molecular characterization of Out-cold (Ocd) mutants of Drosophila melanogaster, which produce a dominant, X-linked, cold-sensitive paralytic phenotype. From its initial 1.5-Mb cytological location within 13F1-16A2, P-element and SNP mapping reduced the Ocd critical region to <100 kb and to six candidate genes: hangover, CG9947, CG4420, eIF2a, Rbp2, and paralytic (para). Complementation testing with para null mutations strongly suggests Ocd and para are allelic, as does gene rescue of Ocd semilethality with a wild-type para transgene. Pesticide resistance and electrophysiological phenotypes of Ocd mutants support this conclusion. The para gene encodes a voltage-gated sodium channel. Sequencing the Ocd lines revealed mutations within highly conserved regions of the para coding sequence, in the transmembrane segment S6 of domain III (I1545M and T1551I), and in the linker between domains III and IV (G1571R), the location of the channel inactivation gate. The G1571R mutation is of particular interest as mutations of the orthologous residue (G1306) in the human skeletal muscle sodium channel gene SCN4A are associated with cases of periodic paralysis and myotonia, including the human cold-sensitive disorder paramyotonia congenita. The mechanisms by which sodium channel mutations cause cold sensitivity are not well understood. Therefore, in the absence of suitable vertebrate models, Ocd provides a system in which genetic, molecular, physiological, and behavioral tools can be exploited to determine mechanisms underlying sodium channel periodic paralyses.