Gck Conditional Knockout mouse models

Glucokinase, encoded by Gck as the mouse ortholog of human GCK, is hexokinase IV, a monomeric enzyme with low glucose affinity, sigmoidal kinetics, no product inhibition by glucose-6-phosphate, and an allosteric activator site distinct from the catalytic cleft, properties that let it act as the glucose sensor of pancreatic beta cells and hepatocytes, where Gckr-encoded regulatory protein sequesters it in the nucleus until fructose-1-phosphate releases it. Heterozygous inactivating mutations produce GCK-MODY with a raised glucose threshold for insulin release, while activating mutations cause congenital hyperinsulinism, and homozygous null mice die perinatally from severe diabetes, so heterozygous or tissue-restricted conditional alleles are the workable designs. Beta-cell deletion using Ins1-Cre interrogates secretion thresholds, hepatocyte deletion using Alb-Cre interrogates glucose disposal and glycogen synthesis, activating knockins model hyperinsulinism, and humanization enables glucokinase activator pharmacology. Hexokinases 1 through 3 have far lower Km and cannot reconstitute sensing, so compensation is not a confound.

Tissue restricted knockout of Gck keeps wild type function everywhere else. Breeding is often more robust, and the setup mirrors patient biology where mutations arise in a subset of cells.