I came to Okamoto’s Lab as I wanted to make a study of developmental biology using zebrafish. Currently, I am studying the genes involved in sensory neuron development. Because of the lack of the experience and knowledge in this area, I always need the effort to overcome. What I’m aiming at is the expansion of knowledge in sensory neuron development and my capabilities through my effort.
The molecular mechanisms of sensory neuron axogenesis.
The sensory neurons have unique morphological appearance. They have two
axons, one is the central axon which project into the CNS (central nervous
system) region such as the spinal cord, and the other is the peripheral
axons which innervates into the peripheral tissues to respond to the external
In conventional neurons, the axons express Tau-1 protein while the dendrites express MAP-2 protein. These structures are distinct from each other both functionally and morphologically. Although there are many studies on how dendrites and axons are formed, there are few studies about how central and peripheral axons of sensory neuron are specified. In previous study, we have demonstrated that peripheral axons of sensory neurons are completely abolished in zebrafish embryo overexpressing the LIM domain of Islet-2 (Segawa et al.:Neuron, vol.30, 423-436, 2001). To find the molecules which regulate the formation of peripheral axons of sensory neurons in the Islet-2 signaling cascade, we have created cDNA library from trigeminal sensory neurons of zebrafish larvae and collected about 1,000 independent clones.
Most of clones were known genes which implicated in signal transduction, transcription and cytoskeltal formation but few clones show no similarity with any known genes. We performed whole-mount in situ hybridization for these clones to compare expression patterns between the wild-type and the LIMIslet-2 overexpressing embryo. Most of clones show CNS or sensory neuron-specific expression patterns and the expression level of these genes were affected by the overexpression of the LIM domain of Islet-2. Loss of function and gain of function studies of these clones, whose function are unknown, showed that these clones might be involved in the development of peripheral axons or the formation of neural circuitry. I believe that reverse-genetical approach will tell us new molecules involved in Islet-2 signaling cascade and development of sensory neurons.