Meeting Abstract
S3.2-2 Saturday, Jan. 4 11:00 How a single gene twists a snail KURODA, Reiko*; ABE, Masanori; Tokyo Univ. of Science; Tokyo Univ. of Science rkuroda@rs.tus.ac.jp
Gastropod Lymnaea (L.) stagnalis has unique features, i.e. , the chirality, the sinistrality and the dextrality, is hereditary, determined by a single locus that functions maternally at the very early embryonic stage. Both left- and right-handed snails exist in nature with the dextral one being dominant. Thus, L. stagnalis is ideal to study “chiromorphology”, i.e., to study the organization process from molecules (genes and proteins), to cells, to organs and to individual organisms through chirality. We have shown, by creating mirror-image fertile creatures as a result of blastomere manipulation, that the chirality of shell coiling is determined by the blastomere arrangement at the third cleavage which is dictated by the handedness determining gene. We have also revealed that the blastomere arrangement regulates asymmetric expression of nodal-Pitx genes in the later development. Further investigation on the expression pattern of nodal – Pitx genes during the development for both the dextral and sinistral L. stagnalis embryos have revealed interesting similarity and dissimilarity with the vertebrates. For example, in both the dextral and sinistral embryos, nodal expression was first detected during the as early as 33-49 cell stages in a specific blastomere which is destined to develop into ectoderm, on the right side for the dextral and on the left side for the sinistral embryos following the third cleavage chirality. The gene expression region extended during the course of development, but was confined only to the left or the right side of embryos, and was mirror images of each other throughout the development. The expression continued towards the late developmental stage when the asymmetrical morphology was noticeable and the shell started to develop. The feature is clearly different from the vertebrates’ which shows asymmetric expression of nodal in the lateral plate mesoderm only transiently at the late developmental stage.
