Complete loss of PAX4 causes transient neonatal diabetes in humans

Objective

Gene discovery studies in individuals with diabetes diagnosed within 6 months of life (neonatal diabetes, NDM) can provide unique insights into the development and function of human pancreatic beta-cells.

Methods

We performed genome sequencing in a cohort of 43 consanguineous individuals with NDM in whom all the known genetic causes had previously been excluded. We used quantitative PCR and RNA-sequencing in CRISPR-edited human induced pluripotent stem cells (iPSCs), and CUT&RUN-sequencing in EndoC-βH1 cells to investigate the effect of PAX4 loss on human pancreatic development.

Results

We describe the identification of homozygous PAX4 loss-of-function variants in 2 individuals with transient NDM: a p.(Arg126∗) stop-gain variant and a c.-352_104del deletion affecting the first 4 PAX4 exons. We confirmed the p.(Arg126∗) variant causes nonsense mediated decay in CRISPR-edited iPSC-derived pancreatic endoderm cells. Integrated analysis of CUT&RUN-sequencing in EndoC-βH1 cells and RNA-sequencing in PAX4-depleted islet stem cell models identified genes directly regulated by PAX4 involved in both pancreatic islet development and glucose-stimulated insulin secretion.

Conclusion

We report the first human cases of complete loss of PAX4, establishing it as a novel cause of NDM and highlighting its role in human beta cell development. Both probands had transient NDM which remitted in early infancy but relapsed at the ages of 2.4 and 6.7 years, demonstrating that in contrast to mouse models, PAX4 is not essential for the development of human pancreatic beta-cells.