Clock T3111C and Per2 C111G SNPs do not influence circadian rhythmicity in Italian healthy population

A possible interaction between human circadian rhythmicity and polymorphisms in genes regulating the sleep-wake cycle (“clock genes”) have been documented in the past few years. However, these data are controversial, and data both corroborating and denying them have been reported. In particular, a T3111C Clock polymorphism has been associated with human evening preference initially, but not confirmed in additional studies. Moreover, the C111G of the Per2 gene has been associated with the “morning larks” chronotype in one study, not yet confirmed in additional studies. In order to provide more insights in this field, we have therefore performed the present study to evaluate whether the Per2 C111G and Clock T3111C polymorphysms may influence sleep circadian rhythmicity in a sample of 158 Italian healthy volunteers. The possible relationship between both polymorphisms and human circadian rhythmicity (morningness, eveningness or intermediate)was also investigated. No differences in Per2 C111G and Clock T3111C allele and genotype frequencies were found between the groups. Furthermore, none of the combined Clock T3111C- Per2 C11G genotypes resulted more frequent in one group compared to the others. Present results do not support a hypothesis on the role of these polymorphisms in the circadian phenotypes, at least in Italian population.