0018 Whole Genome Sequencing Study Identifies Novel Variants Associated with Intrinsic Circadian Period in Humans

Introduction Non-24 is a circadian rhythm disorder in which the master body clock runs either slightly earlier or, more commonly in the disorder, longer than 24 hours. Methods We conducted the first whole genome sequencing study of a non-24 population of 174 individuals that we identified as being totally blind with Non-24 Disorder. We have directly tested the association between SNPs and circadian period length (tau) (n=69). Linear regression corrected for PCs and covariates identified a strong signal in HCN1, Brain Cyclic Nucleotide-Gated Channel 1, HCN1. Results HCN1 channel is responsible for the feedback on the rods regulating the dynamic range of light reactivity under dim or intermediate light conditions. Minor allele rs72762058 associated with longer tau, a difference of 12 minutes, and mean tau of 24.71. In Drosophila there is only one HCN channel encoding gene, DmIh. Interestingly, DmIh mutant flies display alterations in the rest:activity pattern, and altered circadian rhythms, specifically, arrhythmic behavior or a shorter period in constant darkness. We report a variant that associated with longer tau. In addition, we identify others variants that strongly associate with tau, such as a missense variant (rs16989535), (minor allele associated with longer tau), within DEPDC5, GATOR Complex Protein). Subjects carrying the rare allele have a period > 25.2. DEPDC5 is part of GATOR1 complex, together with NPRL2 and NPRL3acts to inhibit the mTORC1 pathway. The GATOR1 seizure phenotype consists mostly of focal seizures, often sleep-related and drug-resistant and is associated with focal cortical dysplasia (20%). mTOR signaling is part of the photic entrainment pathway in the SCN, it regulates autonomous clock properties in a variety of circadian oscillators. Light-induced mTORC1 activation appears to be important for photic entrainment of the SCN clock, as rapamycin modulates light-induced phase shifts of wheel-running and body temperature rhythms in mice. Conclusion We identify variants in HCN1 and DEPDC5 implicated in significantly longer tau. Knowledge of the circadian clock and period length is not only essential for understanding of the basic clockwork mechanisms but also could provide insights into mechanistic links between circadian dysfunctions and human diseases such as epilepsy. Support Vanda Pharmaceuticals