NATIONAL INSTITUTE FOR BASIC BIOLOGY
DIVISION OF MOLECULAR NEUROBIOIOGY
- Masaharu Noda
- Research Associates:
- Nobuaki Maeda
- Graduate Students:
- Hiroki Hamanaka
- Visiting Fellow:
- Haruyuki Matsunaga *
- Technical Stafff:
- Tomoko Mori
- ( * from Environmental Health Science Laboratory, Sumitomo Chemical
The principal interest of this division is molecular mechanisms that govern
the development of the vertebrate central nervous system. Our efforts are
currently focused on projects to reveal the molecular bases of neuronal cell
migration and neuronal network formation.
I. Molecular basis of neuroblast migration
- In the developing central nervous system, migration of post-mitotic
neurons is the key process through which laminated and/or nucleated
structures form out of the uniform neuroepithelium. Thus, to establish
the functional neuronal network, the course of neuroblast migration
must be precise with the combination of radial and tangential movement.
Although many adhesion molecules are known to be expressed in the
neural tissue, the molecular basis of neuroblast migration remains to
- T6 1 antigen is a good candidate of the T6 1 antigen is a good
candidate of the molecule which is responsible for the neuroblast
migration in the radial direction. Monoclonal antibody T61 was
originally characterized by its inhibitory activity on neurite
outgrowth from chick retinal explants in vitro. However, it turned out
recently that neuroblast migration was inhibited when the T61 producing
hybridoma was injected in the ventricle of the developing midbrain of
chick embryos. As far as we know, this is the first example in which an
antibody inhibited neuroblast migration in vivo. molecule which is
responsible for the neuroblast migration in the radial direction.
Monoclonal antibody T61 was originally characterized by its inhibitory
activity on neurite outgrowth from chick retinal explants in vitro.
However, it turned out recently that neuroblast migration was inhibited
when the T61 producing hybridoma was injected in the ventricle of the
developing midbrain of chick embryos. As far as we know, this is the
first example in which an antibody inhibited neuroblast migration in
- The expression of T61 antigen is restricted to the neural tissue, and
the distribution within the tissue is rather uniform.
Immunocytechemistry of primary culture cells showed that only neuronal
cells express the antigen. The finding that T61 antigen is concentrated
at the filopdia of growth cone is consistent with the presumptive
function of this molecule in the cell migration. The T61 detects
several bands including a major 440kD band by Western blotting and
immunoprecipitation. These results suggest that T61 antigen is a novel
molecule. Screening of (RAMDA)gt 11 library prepared from chick brain
with T61 gave rise to many positive signals with various intensity.
Nucleotide sequence analysis revealed that these clones are derived
from several different mRNAs. We are now trying to identify the
authentic cDNA clone from them.
II. Proteoglycan and brain development
- Proteoglycans have been recognized to play important roles in the
regulation of cell growth, differentiation and adhesion. The vertebrate
brain also contains many kinds of proteoglycans, which are considered to
be involved in the neuronal migration, axon guidance and axonal
outgrowth. 6B4 proteoglycan is a brain specific large chondroitin
sulfate proteoglycan with a 300-kDa core protein. This proteoglycan has
the soluble and membrane-bound forms, and its expression is dynamically
regulated during development of the brain. In the adult rat hindbrain,
6B4 proteoglycan is selectively expressed around the neurons
constituting the cerebellar mossy fiber system. In the early postnatal
animals, the expression of 6B4 proteoglycan is highly correlated with
the synapse formation of this system, suggesting that 6B4 proteoglycan
plays important roles in the cerebellar circuit formation.
- To investigate this possibility, we developed an in vitro reconstitution
system of cerebellar circuits, in which slices of cerebellum and
pontine nuclei were cocultured. The latter is a major precerebellar
nuclei from which many mossy fibers project to the cerebellum in vivo.
During long-term culture (2 3 weeks), Purkinje cells developed
well-arbored dendrites and projected to the deep cerebellar nuclei as
revealed by anti-InsP3 receptor monoclonal antibody staining (Fig. 1A).
On the other hand, the pontine fibers projected to the cerebellar
granule cell layer as shown by Dil staining (Fig. 1B). Such a projection
pattern is very similar to that observed in vivo. We are now studying
the function of 6B4 proteoglycan in the fiber projection and the neural
circuit formation using this system.
- Noda, M. (1993) Structure and function of sodium channels. In Molecular
Basis of lon channels and Receptors Involved in Nerve Exitation,
Synaptic Transmission and Muscle Contractions. Annals of The New York
Academy of Sciences. Vol. 707, pp. 20-37.