Single Nucleus Sequencing of Human Colon Visceral Smooth Muscle Cells, PDGFRα Cells, and Interstitial Cells of Cajal

Background and AimsSmooth muscle cells (SMCs), Interstitial cells of Cajal (ICCs), and PDGFR+ cells (PCs) form a functional syncytium in the bowel known as the SIP syncytium. The SIP syncytium works in concert with the enteric nervous system (ENS) to coordinate bowel motility. However, our understanding of individual cell types that form this syncytium and how they interact with each other remains limited, with no prior single cell RNAseq analyses focused on human SIP syncytium cells. MethodsWe analyzed single-nucleus RNA sequencing data from 10,749 human colon SIP syncytium cells (5572 SMC, 372 ICC, and 4805 PC nuclei) derived from 15 individuals. ResultsConsistent with critical contractile and pacemaker functions and with known ENS interactions, SIP syncytium cell types express many ion channels including mechanosensitive channels in ICCs and PCs. PCs also prominently express ECM-associated genes and the inhibitory neurotransmitter receptor for vasoactive intestinal peptide (VIPR2), a novel finding. We identified two PC clusters that differ in expression of many ion channels and transcriptional regulators. Interestingly, SIP syncytium cells co-express 6 transcription factors (FOS, MEIS1, MEIS2, PBX1, SCMH1, and ZBTB16) that may be part of a combinatorial signature that specifies these cells. Bowel region-specific differences in SIP syncytium gene expression may correlate with regional differences in function, with right (ascending) colon SMCs and PCs expressing more transcriptional regulators and ion channels than SMCs and PCs in left (sigmoid) colon. ConclusionThese studies provide new insights into SIP syncytium biology that may be valuable for understanding bowel motility disorders and lead to future investigation of highlighted genes and pathways. SynopsisIn this first single nucleus RNASeq analysis of human SIP syncytium, we identify novel features of SIP syncytium cells, including two types of PDGFR+ cells, a SIP-specific combinatorial transcription factor signature, and colon region differences in gene expression.