Evolutionary Neurobiology Unit (Hiroshi Watanabe)
While the origin of the nervous system is one of the most exciting questions in biology, the origin of neurons and the evolution of the central nervous system (CNS) are not well understood. In particular, the physiological nature of the first neurons has not been elucidated, and likewise it remains unsolved whether the CNSs of extant bilaterians began with an organized array of nerve net or by a primordial neuronal aggregation. Understanding molecular and cellular features of the nervous systems of the extant basal metazoans - early-branching animal lineages including poriferans, placozoans, ctenophores, and cnidarians - is pivotal to answering these questions. Recent genomic and cellular studies on model basal metazoans have provided new genetic insights into our understanding of the early evolutionary processes of the cellular “neuronalization” and the neural centralization.
Our research projects currently include (1) the anatomical and physiological dissections of the nervous systems of the basal metazoans, mainly on diffused and regionally condensed nervous systems of cnidarians, and (2) the analysis of genetic mechanism(s) underlying development of the regionalized (semi-centralized) nervous system of cnidarians. Our unit also carries out (3) a comprehensive analysis chemical neurotransmission among the basal metazoan lineages. We combine cutting-edge genetic, neuroscientific and neuroimaging techniques on cnidarians and other basal metazoans, and phylogenetic analysis to reconstruct the early evolutionary processes of the nervous system.