A Non-Coding Disease Modifier of Pancreatic Agenesis Identified by Genetic Correction in a Patient-Derived iPSC Line.

GATA6 is a critical regulator of pancreatic development, with heterozygous mutations in this transcription factor being the most common cause of pancreatic agenesis. To study the variability in disease phenotype among individuals harboring these mutations, a patient-induced pluripotent stem cell model was used. Interestingly, GATA6 protein expression remained depressed in pancreatic progenitor cells even after correction of the coding mutation. Screening the regulatory regions of the GATA6 gene in these patient cells and 32 additional agenesis patients revealed a higher minor allele frequency of a SNP 3' of the GATA6 coding sequence. Introduction of this minor allele SNP by genome editing confirmed its functionality in depressing GATA6 expression and the efficiency of pancreas differentiation. This work highlights a possible genetic modifier contributing to pancreatic agenesis and demonstrates the usefulness of using patient-induced pluripotent stem cells for targeted discovery and validation of non-coding gene variants affecting gene expression and disease penetrance.