Reiko Kuroda
Tokyo University of Science, Japan
Title: How is the chirality information transferred during the mollusk development?
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 and have created fertile snails of mirror-image body plan by mechanically manipulating the blastomeres at this stage. In this talk, we shall show that nodal expression started at the 33-49 cell stage and was confined only to the left or the right side of embryos, in a mirror-image manner for the sinistral and the dextral snails, throughout the development until the shell was getting formed. The mechano-manipulation reversed the entire expression. Thus, the blastomere arrangement at the 8-cell stage regulates the asymmetric expression of nodal/Pitx genes. At the 24-cell stage, the organizer macromere 3D moved to the central location of vegetal side, filled almost entire cleavage cavity where it contacted with micromeres. MAPK (mitogen-activated protein kinase) was activated in 3D macromere 30 - 60 min. after embryo reached the 24 cell stage. Treatment with U0126, a specific inhibitor of MEK (MAPK/ERK kinase), at the 4-8 cell stage completely inhibited the expression of nodal and its downstream Pitx, whereas, similar treatment at the 24-cell stage after the activation of MAPK did not inhibit the gene expressions. These results clearly indicate that chirality determined at the 8-cell stage is transferred to the 24-cell stage via spiral cleavage and MAPK at the 24-cell stage controls the left-right asymmetric expression of nodal/Pitx genes.