Cry1, short for Cryptochrome1, is a core component of the mammalian circadian clock, playing a crucial role in regulating ∼24-hour rhythms in various behavioral and physiological processes [1,4]. It is involved in the negative feedback loop of the circadian clock mechanism along with genes like Per1, Per2, and Cry2. Additionally, it has implications in processes such as drug metabolism regulation in the liver and glucose homeostasis maintenance [2,3].

In mouse models, ablation of Cry1 in mice reduced hepatic CYP2A5 expression, blunted its diurnal rhythms, decreased CYP2A5 activity, and exacerbated coumarin-induced hepatotoxicity, indicating that Cry1 positively regulates CYP2A5 expression and rhythms through repression of E4BP4 [2]. In diabetic mice, a reduction in hepatic Cry1 protein, stimulated by elevated E3 ligase FBXL3-dependent proteasomal degradation, contributed to hyperglycemia. GSK3β-induced Cry1 phosphorylation further potentiated this degradation, and GSK3β inhibitors decreased hepatic glucose production by facilitating Cry1-mediated FOXO1 degradation [3].

In conclusion, Cry1 is essential for maintaining normal circadian period, regulating drug metabolism in the liver, and maintaining glucose homeostasis. Studies using gene knockout mouse models have provided valuable insights into the role of Cry1 in diabetes-related hyperglycemia and the regulation of drug-metabolizing enzymes, helping us understand the underlying biological mechanisms and potentially providing new strategies for treating related diseases.