Neurofilament ICs were ascertained in all brain regions and appeared to shape gene expression in diverse neuronal populations. The expression of genes with the strongest Neurofilament IC contributions tended to covary both within and across neuronal types. Among interneurons, Neurofilament IC cell loading was most prominent in fast-firing Pvalb+ populations. In frontal cortex interneuron cluster 2, expression levels of the genes strongly contributing to the Neurofilament IC – including Nefh, Kcnc3, Syt2, and Nefm – were continuously distributed and strongly correlated among Pvalb+ interneurons but lower and less correlated among Sst+ interneurons (Figure 3B–D). In the hippocampus, Pvalb± interneurons exhibited high cell loading for the Neurofilament IC, as did the Pvalb± “prototypical” neurons of the GPe (Mallet et al., 2012; Saunders et al., 2016) (Data S5). We ascertained a similar pattern among cortical glutamatergic (Data S5) and subcortical neuromodulatory (Figure 7O) populations.
