Modeling Phenotypic Heterogeneity Of Glycogen Storage Disease Type Ia Liver Disease In Mice By Somatic Crispr/Cas9-Mediated Gene Editing

Patients with Glycogen Storage Disease type 1a (GSD Ia) primarily present with life-threatening hypoglycemia and display severe liver disease characterized by hepatomegaly. Despite strict dietary management, long-term complications still occur, amongst which liver tumor development. Variations in residual glucose-6-phosphatase (G6PC1) activity likely contribute to phenotypic heterogeneity in biochemical symptoms and complications between patients. However, lack of insight into the relationship between G6PC1 activity and symptoms/complications, and poor understanding of the underlying disease mechanisms pose major challenges to provide optimal healthcare and quality of life for GSD Ia patients. Currently available GSD Ia animal models are not suitable to systematically investigate the relationship between hepatic G6PC activity and phenotypic heterogeneity, or the contribution of gene-gene interactions in the liver. To meet these needs, we generated and characterized a novel hepatocyte-specific GSD Ia mouse model using somatic CRISPR/Cas9-mediated gene editing. Hepatic G6pc editing reduced hepatic G6PC activity up to 98% and resulted in failure to thrive, fasting hypoglycemia, hypertriglyceridemia, hepatomegaly, hepatic steatosis, and increased liver tumor incidence. This approach was furthermore successful to simultaneously modulate hepatic G6PC and ChREBP, a transcription factor that is activated in GSD Ia and protects against hepatic steatosis under these conditions. Importantly, it also allowed to model a spectrum of GSD Ia phenotypes in terms of hepatic G6PC activity, fasting hypoglycemia, hypertriglyceridemia, hepatomegaly and hepatic steatosis. In conclusion, we show that somatic CRISPR/Cas9-mediated gene editing allows to model a spectrum of hepatocyte-borne GSD Ia disease symptoms in mice, and to efficiently study gene-gene interactions in the liver. This approach opens new perspectives for translational research and will likely contribute to novel and personalized treatments for GSD Ia and other genetic liver diseases.