Genome-edited zebrafish model of ABCC8 loss-of-function disease

KATP channel gain- (GOF) and loss-of-function (LOF) mutations underlie human neonatal diabetes mellitus (NDM) and hyperinsulinism (HI), respectively. Genetically modified mice with transgenic overexpression of GOF mutations recapitulate many features of human NDM but, importantly, there are currently no gene knock-in mouse models of GOF mutations. Moreover, while transgenic mice expressing incomplete KATP LOF do reiterate mild hyperinsulinism, KATP knockout animals do not exhibit persistent hyperinsulinism. We have shown that islet excitability and glucose homeostasis are regulated by identical KATP channels in zebrafish. SUR1 truncation mutation (K499X) was introduced into the abcc8 gene to explore the possibility of using zebrafish for modeling human NDM and HI. Patch-clamp analysis confirmed complete absence of channel activity in β-cells from K499X (SUR1-/-) fish. No difference in random blood glucose was detected in heterozygous SUR1+/- fish, nor in homozygous SUR1-/- fish, mimicking findings in SUR1 knockout mice. Mutant fish did however, demonstrate impaired glucose tolerance, similar to partial LOF mouse models. In paralleling features of mammalian diabetes and hyperinsulinism resulting from equivalent gain- or loss-of-function mutations, these gene-edited animals provide valid zebrafish models of KATP LOF driven-dependent pancreatic disease.