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Diversity of neocortical interneurons in the neocortex of mouse
Quentin Perrenoud, doctorant Crédits : ESPCI ParisTechGABAergic internereurons are crucial components of the neocortical network, and the functional characterization of the neocortex has been greatly hindered by the lack of consensus regarding the way they should be classified.
During my PhD, I studied the diversity of neocortical interneurons. Patch-clamp recordings coupled to single-cell RT-PCR have been performed, on a sample of more than 300 neocortical interneurons, and the arborization of nearly 200 of them has been reconstructed in 3 dimensions. Their charecteristics have been quantified through a set of 56 parameters.
Interneurons had only been seldomly described in layer VI. Using an unsupervised approach relying on electrophysiological, morphological and molecular parameters, we identified four classes of layer VI GABAergic interneurons. The distributions of GABAergic interneurons expressing characteristic markers were mapped across the radial extent of layer VI by immunostaining, showing that distinct population accumulate in particular sublayers. We have then undertaken to characterize the diversity of GABAergic interneurons across all neocortical layers. Relying on electrophysiological and molecular properties, the classes of interneurons which were characterized in layer VI were found again in our complete sample. However, by analyzing the separation of these groups, we found that a fraction of our sample presented phenotypes which were intermediary to particular classes.
Thus, this work suggest that neocortical interneurons do segregate into several populations, but that these groups are not separate classes but are better conceived as phenotypical archetypes.
Keywords : neocortex, interneurons, unsupervised clustering, continuum