^{Genomics and Molecular Biology}

Biography

Biography: Reiko Kuroda

Abstract

Body handedness of gastropod Lymnaea stagnalis is determined by a single gene locus that functions maternally. We have previously shown that the gene dictates the cytoskeletal dynamics at the third cleavage (from the fourth to the eight-cell stage), and only the embryos of dominant chirality exhibit SD (spiral deformation) and SI (spindle inclination) at this stage. Further, we could create fertile snails of mirror-image body plan by altering the chirality of blastomeres through mechanical manipulation at this stage. In this talk, the identifi cation of the handedness-determining gene will be discussed. Using pure dextral (DD) and sinistral (dd) strains as well as its F2 through to F10 backcrossed lines, the single handedness determining-gene locus was mapped by genetic linkage analysis, BAC cloning and chromosome walking. We have identifi ed the actin related diaphanous gene Lsdia1 as the candidate. Th ere are tandemly-repeated highly-homologus genes, Lsdia1 and Lsdia2. Although the cDNA and derived amino acid sequences of the genes are very similar, we could discriminate the two genes/proteins in our molecular biology experiments. Th e Lsdia1 gene of the sinistral strain carries a single point mutation which causes a frameshift mutation abrogating full-length LsDia1 protein expression. In the dextral strain, it is already translated prior to oviposition. Expression of Lsdia1 (only in the dextral strain) and Lsdia2 (in both chirality) decreases aft er the 1-cell stage, with no asymmetric localization throughout.