CENTER FOR TRANSGENIC ANIMALS AND PLANTS

I. Research supporting activity

NIBB Center for Transgenic Animals and Plants was established in April 1998 to support researches using transgenic and gene targeting techniques in NIBB. We are now planning on the construction of the center building.

The expected activities of the Center are as follows:
1. Provision of information, materials and techniques to researchers.

2. Equipment of various instruments to analyze mutant animals and plants.

3. Development of novel techniques related to transgenic and gene targeting technology.

II. Academic activity

We are studying the functional role of Nax sodium channel in collaboration with Division of Molecular Neurobiology. Nax was long classified as a subfamily of voltage-gated sodium channels (NaChs) that serve to generate action potentials in electrically excitable cells such as neuronal and muscle cells. Comparing with the other NaChs, however, Nax has unique amino acid sequences in the regions, which are known to be involved in ion selectivity and voltage-dependent activation and inactivation, suggesting that it must have specific functional properties. To clarify the functional role of Nax, Nax-deficient mice were generated and the physiological phenotypes have been examined. Behavioral studies suggested that the Nax channel plays an important role in the central sensing of body-fluid sodium level and regulation of salt intake behavior. Ion imaging and electrophysiological studies in vitro also suggested that Nax is an extracellular sodium-level sensitive sodium channel. More recently, we found that Nax is expressed in non-myelinating Schwann cells and alveolar type II cells in addition to the neurons and ependymal cells in the circumventricular organs (CVOs). Nax is thus likely to be involved in reception of sodium-level in body fluids at the CVOs and sodium absorption in the visceral nervous system and in the lung.

Fig. 1 Nax sodium channel is expressed in non-myelinating Schwann cells. Immuno-electron micrographs of a region underneath fungiform taste buds stained with anti-Nax antibody. Arrowheads indicate immuno-positive non-myelinating Schwann cells. Arrows indicate the myelin sheath, and asterisks indicate myelinated axons. Scale bars: 1 mm in (A) and 400 nm in (B), respectively. We also found the Nax-expression in the alveolar type II cells. Nax expressed in these cells is likely to be involved in sodium absorption in the peripheral nervous system and in the lung.

Publication List

Hiyama, T.Y., Watanabe, E., Ono, K., Inenaga, K., Tamkun, M.M., Yoshida, S. and Noda, M. (2002) Nax channel involved in CNS sodium-level sensing. Nat. Neurosci. 5 511-512

Watanabe, E., Hiyama, T.Y., Kodama, R. and Noda, M. (2002) Nax sodium channel is expressed in non-myelinating Schwann cells and alveolar type II cells in mice. Neurosci. Lett. 330, 109-113

Zubair, M., Watanabe, E., Fukada, M. and Noda, M. (2002) Genetic labeling of specific axonal pathways in the mouse central nervous system. Eur. J. Neurosci. 15, 807-814