Deciphering Pancreatic Islet β Cell and α Cell Maturation Pathways and Characteristic Features at the Single-Cell Level

Abstract

Pancreatic β and α cells play essential roles in maintaining glucose homeostasis. However, the mechanisms by which these distinct cell populations are generated, expand, and mature during pancreas development remain unclear. In this study, we addressed this critical question by performing a single-cell transcriptomic analysis of mouse β and α cells sorted from fetal to adult stages. We discovered that β and α cells use different regulatory strategies for their maturation and that cell proliferation peaks at different developmental times. However, the quiescent and proliferative cells in both the β lineage and α lineage are synchronous in their maturation states. The heterogeneity of juvenile β cells reflects distinct cell-cycling phases, origins, and maturation states, whereas adult β cells are relatively homogeneous at the transcriptomic level. These analyses provide not only a high-resolution roadmap for islet lineage development but also insights into the mechanisms of cellular heterogeneity, cell number expansion, and maturation of both β and α cells.

Defining multistep cell fate decision pathways during pancreatic development at single‐cell resolution

“…To obtain differentiated a cells, we generated a Gcg-P2A-GFP mouse strain ( Fig EV1C) in which a-cell identity was validated by immunostaining of glucagon in islets ( Fig EV1D) and by sc-RNA-seq of E17.5 GFP + cells from this strain. Principal component analysis (PCA) showed that these cells clustered with the E17.5 a cells sequenced in our previous study (Qiu et al, 2017a; Fig EV1E). Therefore, this Gcg-P2A-GFP mouse strain can be used to label a cells.…”

“…The simultaneous principal curves indicate the developmental pathways of these cells. Data on E17.5-P60 quiescent b and a cells from our published study (Qiu et al, 2017a) were integrated into this PCA. F…”

“…The EP4 cells are the fourth branching node, from which islet lineage allocation begins. Combined with our previous data (Qiu et al, 2017a), we mapped the entire aand b-cell developmental pathways from the EP stage to the mature stage. Therefore, in addition to the precise fate map defined in this study, our analyses identified many intermediate cell populations along the developmental roadmap ( Fig 8G).…”

“…Our previous study deciphered the mature pathways of both the aand b-lineages from the embryonic stage to the mature stage (Qiu et al, 2017a). Here, when we combined the analyses of the current data with previous data, we defined the entire aand b-lineage developmental pathways ( Fig 8E).…”

Chromatin accessibility variations across pancreatic islet maturation

“…In this study, ATAC-seq and the mRNA microarray analyses have been performed in whole islets and not in FACS-sorted cells or in single cells. Several recent studies have demonstrated a large heterogeneity of gene expression at a single cell level using smFISH or single cell RNA-seq (45)(46)(47)(48). Taking advantage of the heterogeneity of gene expression together with single cell ATAC-seq could shed more light on the transcriptional control of islet maturation and the different cell types involved.…”