BioProject

Inhibitory GABAergic interneurons create different brain activity patterns that correlate with behavioral states. More...

Inhibitory GABAergic interneurons create different brain activity patterns that correlate with behavioral states. In this characterizing study, we used single-cell RNAseq to analyze anatomically- and electrophysiologically-identified hippocampal oriens-lacunosum moleculare (OLM) interneurons. OLMs express somatostatin (Sst), generate feedback inhibition, and play important roles in theta oscillations and fear encoding. Although an anatomically- and biophysically-homogenous population, OLMs comprise two functionally distinct types with presumed different developmental origins, inferred from the expression pattern of serotonin type-3a (5-HT3a, or Htr3a) receptor subunit and 5-HT-excitability in a set of OLMs. To broadly characterize OLM cells, we used the Sst-Cre and the BAC-transgenic Htr3a-Cre mouse lines and separately analyzed SstCre-OLM and Htr3aCre-OLM types. We found a surprisingly consistent expression of Npy in OLMs, which was previously not associated with the identity of this type. Our analyses furthermore revealed uniform expression of developmental origin-related genes, including transcription factors and neurexin isoforms, without providing support for the current view that OLMs may originate from multiple neurogenic zones. Together, we found that OLMs constitute a highly homogenous transcriptomic population. Finally, our results revealed surprisingly infrequent expression of Htr3a in only ~10% of OLMs, and an apparently specific expression of the 5-HT3b subunit-coding gene Htr3b in Htr3aCre-OLMs, but not in SstCre-OLMs. However, additional in situ hybridization experiments suggested that the differential expression of Htr3b may represent an unexpected consequence arising from the design of the Htr3a-Cre BAC transgenic line. Overall design: mRNA profiles of 46 OLM cells (23 Sst line, 23 Htr3a line) Less...