Professor of Veterinary Clinical Genetics Royal Veterinary College Cambridge, England, United Kingdom
Abstract: Background A diabetes-associated missense mutation in KCNJ11, encoding the Kir6.2 subunit of the ATP-sensitive potassium (KATP) channel has been reported in UK Labrador retrievers (LRs). In humans, KCNJ11 mutations disrupt KATP-channel regulation of β-cell insulin secretion.
Hypothesis/Objectives We hypothesised that the canine Kir6.2-D274N mutation (rs851344999) might alter KATP-channel trafficking and metabolic regulation, affecting insulin secretion.
Animals Glycaemic phenotyping was performed in young (≤ 4years), clinically healthy female LRs of all three KCNJ11 genotypes, housed at a US guide dog breeding facility.
Methods The rs851344999 variant was detected by WISDOM PANEL-TM (Antech Diagnostics, Mars Petcare Science & Diagnostics), confirming its presence in US LR populations. KATP-channel surface expression was assessed in HEK293T cells co-expressing Kir6.2 (pore subunit) with an extracellular hemagglutinin-tagged SUR1 (regulatory subunit). Functional properties of wild type and mutant channels were assessed in vitro by patch-clamp recordings. In vivo metabolic parameters, including fasting serum glucose, fructosamine and insulin concentrations were compared across genotypes.
Results Kir6.2-D274N channels showed approximately 40% reduced surface expression, and a small reduction in ATP-dependent inhibition compared with wild-type channels. Fasting glucose and fructosamine concentrations did not differ by genotype; however, fasting serum insulin concentrations were significantly elevated in dogs homozygous for the D274N allele (p < 0.001).
Conclusions and Clinical Importance The Kir6.2-D274N mutation impairs KATP-channel trafficking while reducing ATP-mediated channel inhibition. Further work is needed to determine whether the observed hyperinsulinemia predisposes to future β-cell exhaustion. These findings provide mechanistic insight into canine diabetes pathophysiology and support further investigation of genetically defined disease subtypes.
