Repairing Atp10D in C57Bl/6J mice restores protein expression but does not mitigate metabolic stress from high fat diet.

C57BL/6J mice are widely used in biomedical research and are susceptible to insulin resistance and dyslipidemia when challenged with high fat diets relative to other inbred strains. Interestingly, C57Bl/6J mice contain a naturally occurring premature termination codon in the lipid flippase Atp10D, and previous studies have linked Atp10D to the metabolic disease-prone phenotype in mice and atherosclerotic severity in humans. In this study, we used CRISPR/Cas9 to revert the premature termination codon to the wild-type glutamine codon (Atp10D *817Q) in the C57Bl/6J mouse strain. The RNA transcripts from original and corrected alleles are dually expressed in heterozygous mice, suggesting that the mutant transcript escapes nonsense-mediated decay. Expression of two corrected Atp10D alleles restores wildtype expression levels of the transcript and protein in the liver. When challenged with a high fat diet, Atp10D-/- (original) and Atp10D+/+ (corrected) C57Bl/6J mice showed no significant difference in weight gain, glucose tolerance, or plasma levels of triglycerides, cholesterol, or free fatty acids. However, the female Atp10D+/+ mice displayed an increase in complex glycosphingolipids and a reduction in cardiolipins in the plasma. These results suggest that restoring the expression of Atp10D in C57Bl/6J mice does not reverse insulin resistance and dyslipidemia in response to high fat diet feeding.