The Journal of Neuroscience, May 1, 2002, 22(9):3520-3530
Clonal Architecture of the Mouse Hippocampus
Loren A.
Martin1,
Seong-Seng
Tan2, and
Dan
Goldowitz1
1 Department of Anatomy and Neurobiology, University of
Tennessee Health Science Center, Memphis, Tennessee 38163, and
2 Howard Florey Institute, University of Melbourne,
Parkville VIC 3010, Australia
Experimental mouse chimeras have proven useful in analyzing the
cell lineages of various tissues. Here we use experimental mouse chimeras to study cell lineage of the hippocampus. We examined clonal architecture and lineage relationships of the hippocampal pyramidal cells, dentate granule cells, and GABAergic interneurons. We
quantitatively analyzed like-genotype cohorts of these neuronal populations in the hippocampus of the most highly skewed
chimeras to provide estimates of the size of the progenitor pool that
gives rise to these neuronal groups. We also compared the percentage chimerism across various brain structures to gain insights into the
origins of the hippocampus relative to other neighboring regions of the
brain. Our qualitative analyses demonstrate that like-genotype cohorts
of pyramidal cells are aligned in radial arrays across the pyramidal
cell layer, whereas like-genotype cohorts in the C-shaped dentate gyrus
colonize either the outer shell or inner core of the granule cell layer
in a symmetrical manner. Clonally related populations of GABAergic
interneurons are dispersed throughout the hippocampus and originate
from progenitors that are separate from either pyramidal or granule
cells. Granule and pyramidal cells, however, are closely linked in
their lineages. Our quantitative analyses yielded estimates of the size
of the progenitor pools that establish the pyramidal, granule, and
GABAergic interneuronal populations as consisting of 7000, 400, and 40 progenitors, respectively, for each side of the hippocampus. Last, we
found that the hippocampal pyramidal and granule cells share a lineage
with cortical and diencephalic cells, pointing toward a common lineage
that crosses the di-telencephalic boundaries.
Key words:
dentate gyrus; cell lineage; granule cell; pyramidal
cell; GABAergic interneuron; chimera
Copyright © 2002 Society for Neuroscience 0270-6474/02/2293520-11$05.00/0