Single Cell RNA sequencing of MAFB +/+ and -/- cells at the pancreatic progenitor and beta-like stages

Pancreatic Beta-cells are essential for regulating blood glucose levels. Much of our knowledge relating to human Beta-cell development and function has depended on rodent models, which have provided a blueprint to confirm important cellular features in humans. The advent of next generation sequencing studies, however, has highlighted discrepancies in Beta-cells which exist between mice and men. The precise contribution of such differences has not yet been fully appreciated. Numerous studies have identified MAFB to be present in human Beta-cells postnatally, while its expression is restricted to embryonic and neo-natal Beta-cells in mice. Conversely, the related transcription factor MAFA is only active in mature murine Beta-cells and notably, knockout of MAFB has minimal effect on murine Beta-cell development and function, in contrast to MAFA. Using CRISPR/Cas9-mediated gene editing, coupled with endocrine cell differentiation strategies, we dissect the contribution of MAFB to Beta-cell development and function specifically in humans. MAFB knockout hPSCs have normal pancreatic differentiation capacity up to the progenitor stage, but favor somatostatin- and pancreatic polypeptide–positive cells at the expense of insulin- and glucagon-producing cells during endocrine cell specification. Our results uncover a requirement for MAFB late in the human pancreatic developmental program and identify it as a distinguishing transcription factor within islet cell subtype specification. Taken together, the current study demonstrates that MAFB has synonymous functions in mice and human Alfa and Beta-cell specification and uncovers previously unappreciated roles in other pancreatic endocrine cell types, in particular Gamma-cells. We propose that under-appreciated differences in rodent versus human pancreatic islet biology may be alleviated by expanding genetic observations in animal models by utilizing hPSCs to better model human Beta-cell development and associated disease pathophysiology such as diabetes. MAFB+/+ and MAFB-/- hESCs differentiated towards pancreatic progenitor cells and beta-like cells were digested and prepared using v2 10X single cell kits according to standard protocol, then sequenced using HiSeq4000.