Professor Chihiro Hama

Area and Subject Taught Molecular Neuroscience
Research Theme(s) Roles for synaptic cleft matrix in development of brain functions
Academic Degrees Doctor of Science, University of Tokyo
Keywords for Research Field Brain, Neuron, Synapse, Matrix, Drosophila
Office Phone Number 81-75-705-3120

Research Overview

How the brain expresses a variety of neural function still remains enigmatic. We study regulatory mechanisms of synapse differentiation at molecular levels, and also try to understand a genetic program that globally organizes the circuit formation in the brain. To approach these problems, we employ a small brain of Drosophila, which comprises 105 neurons, only a millionth the size of a human brain. Our research currently focuses on the synaptic cleft matrix, identifying its components, analyzing the process of matrix formation, and revealing roles for matrix in synapse differentiation and brain functions.
The hig (hikaru geneki) gene, identified by a mutant phenotype of reduced locomotor activity (Hoshino et al., Neuron 1993), encodes a secretory protein with multiple CCP domains. Hig protein localizes to the synaptic clefts, forming matrix at cholinergic synapses in the brain (Hoshino et al., Development 1996; Nakayama et al., J. Neurosci. 2014). We also identified another secretory CCP matrix protein, Hasp, which is required for localization of Hig at synaptic clefts (Nakayama et al, 2016). Notably, Hig and Hasp form distinct compartments within individual synaptic clefts. We are currently trying to further identify the proteins that constitute synaptic matrix, and also to reveal how these proteins are organized in order to form functional matrix during synaptogenesis.

Notable Publications and Works in the Last Three Years

  1. Nakayama, M., Suzuki, E., Tsunoda, S., Hama, C. The matrix proteins Hig and Hasp exhibit segregated distribution within synaptic clefts and play distinct roles in synaptogenesis. The Journal of Neuroscience 36, 590-606 (2016).
  2. Nakayama, M., Matsushita, F., Hama, C. The matrix protein Hikaru genki localizes to cholinergic synaptic clefts and regulates postsynaptic organization in the Drosophila brain. The Journal of Neuroscience 34, 13872-13877 (2014).