Transcriptional and temporal heterogeneity of developing α cells revealed by single-cell RNA sequencing

Glucagon (Gcg)-expressing pancreatic α cells play pivotal roles in maintaining glucose and amino acid homeostasis; however, the cellular heterogeneity during α-cell genesis remains unclear. To explore the transcriptional dynamics of developing α cells, single-cell transcriptomics was performed using "Gcg-Timer" embryos, in which newly generated α cells can be sorted from more differentiated α cells by their fluorescence. Green-fluorescent early α cells expressed high levels of key β-cell genes, such as Ins1, Ins2, and Pcsk1, as well as other endocrine-specific mRNAs, including Sst and Ghrl, whereas green/red double-fluorescent late α cells expressed higher levels of Gcg, suggesting temporal maturation during α-cell differentiation. Furthermore, comprehensive analyses of the Gcg-Timer dataset and two independent datasets at different developmental stages revealed that mitochondrial transcripts were more robustly expressed in α cells than in developing β cells. Taken together, single-cell transcriptomics using a time-resolved reporter mouse line demonstrated novel features of temporal and transcriptional heterogeneity of developing α cells.