Fig. 1. A model for the positive and negative feedback loops formed by the interaction of circadian clock genes (modified from the study of Ruan et al. (2021)) . bHLH: basic helix-loop-helix; BMAL1: brain and muscle aryl hydrocarbon receptor nuclear translocator (ARNT)-like 1; CK1δ: casein kinase 1δ; CLOCK: circadian locomotor output cycles kaput; CRY: cryptochrome; DBP: Duffy-binding protein; DEC: differentiated embryo chondrocyte; NFIL3: nuclear factor interleukin 3; PER: period; REV-ERBα/β: nuclear receptor subfamily 1 group D 1/2 (NR1D1/2); ROR: retinoid-related orphan receptor; RORE: ROR/REV-ERB-response element.