GSE192676
Ret loss-of-function decreases neural crest progenitor proliferation and restricts developmental fate potential during enteric nervous system development
The receptor tyrosine kinase gene RET plays a critical role in the fate specification of enteric neural crest cells (ENCCs) during enteric nervous system (ENS) development. Pathogenic RET loss of function (LoF) alleles are associated with Hirschsprung disease (HSCR), which is marked by aganglionosis of the gastrointestinal (GI) tract. ENCCs invade the developing GI tract, proliferate, migrate caudally, and differentiate into all of the major ENS cell types. Although the major phenotypic consequences, and the underlying transcriptional changes from Ret LoF in the developing ENS have been described, its cell type and state-specific effects are unknown. Consequently, we performed single-cell RNA sequencing (scRNA-seq) on an enriched population of ENCCs isolated from the developing GI tract of Ret null heterozygous and homozygous mouse embryos at embryonic day (E)12.5 and E14.5. We demonstrate four significant findings: (1) Ret-expressing ENCCs are a heterogeneous population composed of ENS progenitors as well as glial and neuronal committed cells; (2) neurons committed to a predominantly inhibitory motor neuron developmental trajectory are not produced under Ret LoF, leaving behind a mostly excitatory motor neuron developmental program; (3) HSCR-associated and Ret gene regulatory network genes exhibit distinct expression patterns across Ret-expressing ENCC cells with their expression impacted by Ret LoF; and (4) Ret deficiency leads to precocious differentiation and reduction in the number of proliferating ENS precursors. Our results support a model in which Ret contributes to multiple distinct cellular phenotypes and that Ret LoF contributes to GI aganglionosis in multiple independent ways. Overall design: Modified Smart-Seq2 single-cell RNA-Seq of 1,003 cells from the developing mouse gut (E12.5 & E14.5) in both male and female wild type and Ret homozygous null animals. N=2 replicate animals  for each condition. Varying number of cells passing QC for each condition.