GENES EXPRESSION OF WNT SIGNALING PATHWAY DURING REGENERATIVE PROCESS AND ASEXUAL REPRODUCTION IN HOLOTHURIANS

Abstract

Wnt proteins are the key factors in many morphogenetic processes including the regenerative process. Mammals compared with invertebrates are definitely limited in the ability to regenerate the damaged organs although they have the same conservative molecules of Wnt signaling pathways. To activate regenerative process using Wnt proteins it is essential to study the recovery process in model organisms - echinoderms. Methods. Holothurians were taken from Peter the Great Bay, Sea of Japan as well as from the Gulf of Nha Trang, South China Sea. Evisceration of the holothurians Eupentacta fraudatrix was induced by the injection of distilled water into the coelomic cavity. On the 3^rd, 5^th and 7^th day after evisceration the aqua pharyngeal complex rudiments and anterior area of recovering intestine were prosected. Holothurian Cladolabes schmeltzii was dissected in the middle part of the body into two fragments. The recovering intestine was prosected on the 14^th and 24^th day. In addition there were also the organisms engaged in the process of asexual reproduction (for the gene activity analysis the tissues from the fission spot have been studied). With the sequencing of the transcripts in holothurians the presence of genes WNT1, WNT2, WNT4, WNT6, WNT7, WNT9, WNT10, WNT16 has been determined during regenerative process and asexual reproduction. Results. In E. fraudatrix the genes expression WNT4, WNT6 occurred only at the late phases of regenerative process. In C. schmeltzii WNT2, WNT10, WNT16 activated at the early phases of recovery, WNT1, WNT2, WNT3, WNT4 and WNT7 - at the late phases. With asexual reproduction of C. schmeltzii the transcripts WNT1, WNT2, WNT4, WNT7, WNT10 have been revealed. The other members of Wnt signaling pathway have also been found: β-catenin, frizzled, dishevelled. Conclusions. The differences in the spectrum of Wnt signaling molecules in various species of holothurians obviously reflect different morphogenesis mechanisms in their anterior and back body structures. Identified WNT genes sequences have only 45-67 % of the similarity level with homologous genes of the sea urchin Strongylocentrotus purpuratus, which is explained by a large evolutionary gap between the sea urchins and holothurians. Perhaps in the studied processes WNT genes make a concentration gradient, thereby determining the organs’ rudiment areas or they directly control the regenerative process, making the cells to migrate and form the organs.