Age-dependent replacement of neural-crest derived enteric neurons by a novel mesodermal lineage and its functional consequences

During fetal development, neural crest precursors give rise to neurons of the enteric nervoussystem (ENS). However, given our evolving understanding of the dynamic nature of the ENS, itis not clear whether this developmental paradigm holds true at different post-natal stages. Here,we show that due to loss of GDNF-RET signaling with age, neural crest-derived neurons un-dergo a progressive decline in numbers. They are replaced by neurons derived from the embry-onic mesoderm which, with increasing age, become the dominant form of neurons in the ENS,and this is associated with functional deficits in intestinal motility. Using single cell transcrip-tomics and immunochemical approaches, we characterize these mesoderm-derived neuronsand show that this novel lineage of neurons expresses MET and is dependent on HGF for itsexpansion. Normal intestinal function in the adult gastrointestinal tract therefore appears to re-quire an optimal balance between these two distinct lineages within the ENS. Two replicate samples of dissociated, postnatal day 60, mouse small intestinal longitudinal muscle-myenteric plexus were prepared and run through the 10x Chromium 3' Single Cell Gene Expression platform (V2.0).在胎儿发育阶段，神经嵴前体细胞（neural crest precursors）可分化为肠神经系统（enteric nervous system, ENS）的神经元。然而，随着学界对肠神经系统动态特性的认知不断深化，目前尚不清楚这一发育范式在不同产后阶段是否依然成立。本研究发现，随着年龄增长，GDNF-RET信号通路（GDNF-RET signaling）的丧失会导致神经嵴来源神经元的数量出现进行性下降。这些神经元会被胚胎中胚层来源的神经元所替代；随着年龄增长，这类神经元会成为肠神经系统内占主导的神经元类型，且该现象与肠道运动功能缺陷密切相关。本研究借助单细胞转录组学（single cell transcriptomics）与免疫化学方法，对这类中胚层来源神经元进行了表征，结果显示该新型神经元谱系表达MET基因，且其扩增依赖于肝细胞生长因子（hepatocyte growth factor, HGF）。因此，成年胃肠道的正常肠道功能似乎需要肠神经系统内这两种不同谱系的神经元维持最佳平衡。我们制备了两份解离后的产后第60天小鼠小肠纵行肌-肌间神经丛重复样本，并将其上机运行10x Chromium 3'单细胞基因表达平台（V2.0版本）。