Authors :
Elizabeth Matthews, PhD – Duke University
Jeffrey Russ, MD, PhD – Duke University
Yongjun Qian, PhD – Peking University
Shengli Zhao, PhD – Duke University
Peyton Thompson, BS – Duke University
Muhib Methani, BS – Duke University
Matthew Vestal, MD – Dartmouth University
Josh Huang, PhD – Duke University
Presenting Author: Derek Southwell, MD PhD – Duke University
Rationale:
GABAergic interneurons (INs) are the principal inhibitory cellular elements of neural circuits, and their dysfunction is a pathophysiologic factor in epilepsy. INs are generated primarily in the embryonic medial and caudal ganglionic eminences (MGE and CGE). Immature MGE- and CGE-derived interneurons disperse throughout the developing cortex and mature into cell types that express diverse functional and circuit properties and differentially engage in epileptogenesis and ictogenesis. The functional properties and circuit organization of these diverse interneuron types are well studied in rodents, however, due to a lack of experimental tools, human INs remain poorly understood. Comparative anatomical & transcriptomic studies indicate a primate-specific expansion of VIP-expressing interneuron populations derived from the CGE. While it has been hypothesized that the expansion & specialization of primate CGE interneurons could give rise to human cognitive abilities and confer specific disease susceptibilities, the circuit functional properties of human CGE interneurons remain unknown.
Methods:
We used CellREADR, a novel RNA sensing tool for cell-type specific access, to study the intrinsic physiological properties (patch clamp recordings with PatchSeq transcriptomics), coordinated population activity (spontaneous calcium imaging), and synaptic outputs (optogenetic activation) of CGE INs in human cortex1. Human cortical tissues were collected from surgical epilepsy patients and cultured as organotypic slices for up to 11 days in vitro.Results:
CellREADR CALB2 (calretinin) sensors accessed CGE INs in organotypic slices. Targeted patch clamp recordings of 62 cells from 9 subjects portrayed the diverse physiological properties of CGE INs. PatchSeq transcriptional characterization of a subset allowed us to align recorded cells to published atlases. A notable feature of many human CALB2 INs was their steep gain & high maximal firing rates. Population activity of GCamp7f-labeled cells did not reveal strongly correlated activity among cells, but the cells’ calcium signaling was sensitive to activation of nACHR. We found that the targeted cell cohort formed functional GABAergic projections with equal frequency onto both excitatory & inhibitory neurons.
Conclusions:
Together these experiments advance a novel approach for cell type-specific access in live human neural circuits. By leveraging CellREADR’s capacity for specific, scalable & programmable cellular access, this study advances tools for human cellular neuroscience while elucidating properties of human cortical inhibitory circuits in epilepsy.Funding:
NIH 1DP2MH140149, Klingenstein-Simons Fund, Whitehall Foundation, Ruth K Broad Foundation