P-92

Expression analysis of serotonergic signal system in Xenopus early embryogenesis

Denis NIKISHIN¹, Stanislav KREMNYOV², Yuri SHMUKLER¹

¹Koltzov Institute of Developmental Biology RAS, ul. Vavilova 26, 119334, Moscow, Russia

²Department of Biology, Lomonosov Moscow State University, Leninskie Gory 1, p. 12, 119991, Moscow, Russia

Serotonin is involved in various embryogenetic processes such as fertilization, cleavage, blastomere interactions, gastrulation, and morphogenesis, and regulates cellular processes such as cell cycle, the state of cytoskeleton, and ciliary motility. There are physiological and biochemical evidences of the important role of serotonin in early embryonic development, but molecular biological data on this are uncommon. We carried out spatiotemporal expression analysis of the serotonergic system components during embryogenesis of Xenopus laevis. We have shown that serotonin receptors and transporters in some or other combinations, are expressed during the whole Xenopus embryogenesis. We have shown that transcripts of serotonin receptors HTR2C and HTR7, serotonin transporter SERT, and vesicular monoamine transporter VMAT2 are part of the maternal mRNA pool. Probably the early embryo cells accumulate serotonin into vesicles by VMAT2 and release it by exocytosis. HTR2C and HTR7 interact with serotonin and activate phosphatidylinositol and cAMP signal pathways respectively, and SERT provides the reuptake of serotonin. Thus, the early embryos have all the components necessary for serotonin signaling via the classical neural mechanism. This is even more intriguing when one considers that it is the neural type of VMAT is expressed in early embryos. This is evidence that the neurotransmitter function of serotonin is secondary, and arose from its more general regulatory function.