Tomato lectin also recognizes a subclass of cells
deep in the tectum, immediately adjacent to the ependymal cells lining
the tectal ventricle, and disappears soon after migration along radial
glia begins. This is where neural stem cells, cells that give
rise to all the other neurons and glia of the nervous system, are known
to be located. Tomato lectin also stains cells migrating out of
the cerebellum through the white matter and into the deep cerebellar
nuclei. The tomato lectin positive cells do not colocalize with
markers for neurons or oligodendrocytes, but do stain with some (but
not all) markers for neural stem cells or astrocytes (GS, glutamine
synthase). When neural stem cells are cultured as neurospheres,
tomato lectin positive cells appear in the spheres, and these are
different cells than the immature neurons. These results suggest
that tomato lectin is an early marker in the differentiation of neural
stem cells.
Current experiments are focused on 2 major
questions: what are some of the early differentiation markers that
colocalize with tomato lectin? We have a number of different
antibodies that have been reported on immature cells, and
identification of these molecules will help us to characterize the
tomato lectin positive cells. We will stain both tissue sections
and neurospheres to learn more about how these markers are expressed in
relation to tomato lectin. Secondly, are tomato lectin positive
cells still dividing? We will answer this question using
bromodeoxyuridine, a nucleotide analog that gets incorporated into
newly dividing DNA and can be detected with an antibody. Cells
labeled immediately must have divided during treatment; if positive
tomato lectin cells appear later, that argues the tomato lectin
positive cells are no longer dividing and are committed to a
developmental fate.
