CRY1 is a core transcriptional repressor component of the circadian molecular clock that regulates approximately 24-hour rhythms in gene expression and physiological processes 1. CRY1 functions within a transcription-translation feedback loop where it forms complexes with PER proteins to inhibit CLOCK-BMAL1 heterodimers, thereby negatively regulating its own expression and other clock-controlled genes 2. A dominant coding variant in CRY1 causes familial delayed sleep phase disorder (DSPD) by creating an enhanced transcriptional inhibitor with increased affinity for CLOCK and BMAL1, leading to lengthened circadian periods and altered sleep timing 1. This variant affects up to 0.6% of the population and correlates with late sleep patterns 1. CRY1 variants are also associated with cluster headache, particularly in patients with diurnal attack rhythmicity 3. Beyond circadian regulation, CRY1 influences metabolic processes, with polymorphisms interacting with dietary patterns to affect obesity measures 4. Additionally, CRY1 regulates cellular senescence in ovarian granulosa cells through NCOA4-mediated ferritinophagy, with reduced expression linked to age-related fertility decline 5. CRY1 expression can be therapeutically modulated, as demonstrated by butyrate supplementation upregulating CRY1 in ulcerative colitis patients alongside improved inflammation and sleep quality 6.