Mex3a Marks a Slowly Dividing Subpopulation of Lgr5+ Intestinal Stem Cells

Abstract

SUMMARY The intestinal epithelium is continuously regenerated by highly proliferative Lgr5+ intestinal stem cells (ISCs). The existence of a population of quiescent ISCs has been suggested yet its identity and features remain controversial. Here we describe that the expression of the RNA-binding protein Mex3a labels a subpopulation of Lgr5+ cells that divide less frequently and contribute to regenerate all intestinal lineages with slow kinetics. Single cell transcriptomic analysis revealed two classes of Lgr5-high cells, one of them defined by the Mex3a-expression program and by low levels of proliferation genes. Lineage tracing experiments show that large fraction of Mex3a+ cell population is continuously recalled into the rapidly dividing self-renewing ISC pool in homeostatic conditions. Chemotherapy and radiation target preferentially rapidly dividing Lgr5+ cells but spare the Mex3a-high/Lgr5+ population, which helps sustain the renewal of the intestinal epithelium during treatment.

Potential application of cell reprogramming techniques for cancer research

“…Such high-throughput single-cell RNA sequencing technologies have the potential to promote the understanding of cancer generation in the decomposition of heterogeneous cell populations and of the heterogeneity of cells associated with various tumorigenic stages. This technology allows the identification of the cellular subpopulations and the delineation of novel cell markers in the hematopoietic [71], respiratory [72], hepatobiliary [73], and pancreatic [74, 75] lineages, as well as in the intestine [76]. Recent progress in single-cell RNA sequencing led to the identification of the heterogeneous origins of CSCs in gliomas [77], breast cancers [78], myeloid leukemias [79], bladder cancers [80], and colorectal cancers [81].…”

“…For example, trisomy 12 is an aberration that is observed commonly in ESCs and iPSCs [72–75]. Some cell cycle-related genes and NANOG are located on chromosome 12; thus, trisomy 12 might result in alterations in proliferation and reprogramming [76, 77]. The amplification of chromosomes 8 and X, as well as of other chromosomes, was also detected in iPSCs [72, 73].…”

A single-cell survey of the small intestinal epithelium

“…Previous surveys that relied on known markers to purify cell populations 1,2 cannot always fully distinguish between cell types, may identify only subsets of types in mixed populations or fail to detect rare cellular populations or intermediate states. Recent studies 3–7 attempted to overcome these limitations using single-cell RNAseq (scRNA-seq), but have not yet extensively characterized intestinal epithelial cellular diversity.…”

Intestinal Enteroendocrine Lineage Cells Possess Homeostatic and Injury-Inducible Stem Cell Activity

“…Indeed, quiescent +4 label-retaining cells (LRCs) are injury-inducible secretory progenitors that co-express Lgr5, Paneth and enteroendocrine (EE) markers (Buczacki et al, 2013). Mex3a + cells that co-express high levels of Lgr5 are slowly cycling and share common features with LRC(Barriga et al, 2017). Alkaline phosphate-expressing enterocytes repopulate crypts after Lgr5 + ISC ablation but not during homeostasis (Tetteh et al, 2016), suggesting plasticity of the differentiated absorptive enterocyte lineage to support epithelial reconstitution following CBC loss.…”