Single-Cell Analysis Uncovers Clonal Acinar Cell Heterogeneity in the Adult Pancreas

Acinar cells make up the majority of all cells in the pancreas, yet the source of new acinar cells during homeostasis remains unknown. Using multicolor lineage-tracing and organoid-formation assays, we identified the presence of a progenitor-like acinar cell subpopulation. These cells have long-term self-renewal capacity, albeit in a unipotent fashion. We further demonstrate that binuclear acinar cells are terminally differentiated acinar cells. Transcriptome analysis of single acinar cells revealed the existence of a minor population of cells expressing progenitor markers. Interestingly, a gain of the identified markers accompanied by a transient gain of proliferation was observed following chemically induced pancreatitis. Altogether, our study identifies a functionally and molecularly distinct acinar subpopulation and thus transforms our understanding of the acinar cell compartment as a pool of equipotent secretory cells. Overall design: The single-cell RNA-seq library preparation protocol was based on the SMART seq2 protocol (Picelli et al., 2014) with following modifications. Acinar cells were isolated as described in the section Acinar Cell Isolation and Culture and resuspended in DPBS without Ca2+ and Mg2+ (PAN-Biotech). Cells were collected in a volume of 0.5 µL and transferred to a reaction tube containing 4 µL of 6 M guanidine-HCl (Sigma-Aldrich), 0.1% (v/v) Triton X-100 (Sigma-Aldrich) and 1% (v/v) 2-mercaptoethanol (?Sigma-Aldrich). The tube was immediately transferred into liquid nitrogen and kept there for the duration of cell collection. Next, 2.2× RNA SPRI beads (Beckman Coulter) were added directly to the lysis buffer and incubated for 5 min at room temperature. The beads were washed twice with 70% ethanol. Air-dried beads were resuspended in a solution containing 2 µL of H20, 1 µL of oligo(dT) primer, and 1 µL of dNTP Mix (primer and nucleotides used as in Picelli et al., 2014). Twenty-four cells contained ERCC Spike-In RNAs (1:10,000; Mix2, Ambion) Mix in addition to primer and nucleotides. Beads were incubated for 3 min at 72°C, and reverse transcription and PCR (19 cycles) were performed as described by Picelli et al. (2014). PCR product was cleaned up using 0.8× DNA SPRI beads (Beckman Coulter), and air-dried beads were resuspended in 15 µL of H2O. The quality of cDNA library was assessed for each cell on a high-sensitivity DNA Bioanalyzer chip. Subsequent steps (tagmentation, amplification, multiplexing) were done as previously described (Llorens-Bobadilla et al., 2015). The DKFZ Genomics and Proteomics Core Facility conducted sequencing on an Illumina HiSeq2000 sequencer (paired-end 100 bp).

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Wollny D, Zhao S, Everlien I, Lun X, Brunken J, Brüne D, Ziebell F, Tabansky I, Weichert W, Marciniak-Czochra A, Martin-Villalba A