Polyploidy and the Cellular and Areal Diversity of Rat Cortical Layer 5 Pyramidal Neurons

Publication date: 12 September 2017
Source:Cell Reports, Volume 20, Issue 11
Author(s): Johanna Sigl-Glöckner, Michael Brecht
In many species, polyploidy, in which an increase in nuclear DNA content is accompanied by an increase in cell size, contributes to cellular diversity. In the rat visual cortex, most neurons are small and homogeneous in size, while layer 5 cells are heterogeneous, containing some very large neurons. To measure DNA content, we quantified nuclear chromocenters and integrated DNA/DAPI fluorescence. The results suggest that most cortical neurons, non-neuronal cells, parvalbumin-positive interneurons, and large entorhinal layer 2 stellate projection neurons are diploid. In contrast, chromocenter counts and integrated fluorescence are ∼2-fold higher for some excitatory neurons in layer 5, suggesting that large Ctip2-negative and Ctip2-positive layer 5 neurons might be tetraploid. The distribution of putatively tetraploid neurons differed between areas and showed sharp borders aligned with functional subdivisions of the somatosensory cortex. Telomere counting and flow cytometry supported layer 5 polyploidy. We conclude that polyploidy contributes to cellular and areal diversity of rat cortex.

Graphical abstract

Teaser

Cortical principal cell diversity is poorly understood. Sigl-Glöckner and Brecht find that very large principal neurons in layer 5 of rat cortex are polyploid. Putatively tetraploid neurons are differentially distributed across cortical areas and functional subdivisions.


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