From genes to chronotypes: the influence of circadian clock genes on our daily patterns of sleep and wakefulness

The functions of circadian clocks and oscillators depend on a small number of genes. This collection of circadian clock genes forms an autoregulatory feedback loop, and provides the mechanism that underlies the operation of circadian clocks and oscillators in the brain and body (1). The resulting endogenous clocks and oscillators go on to drive diverse rhythms in behavior and physiology. Therefore, it was with some foresight that Hu et al. [2016] surveyed “23andMe” clients on their daily sleep-wake preferences, and performed an extensive genome-wide association study (GWAS) on 89,283 individuals (2). Even with a relatively coarse self-reported measure of “morningness”, the authors were able to identify 15 loci that were associated with preferred wake times, and notably, many of these loci related back to known circadian clock genes. Taken together, this study provides important new evidence that single nucleotide polymorphisms (SNPs) located close to certain clock genes, are associated with meaningful changes in our innate circadian preferences to wake early or to sleep late.