Turco M, Biscontin A, Corrias M, Caccin L, Bano M, Chiaromanni F, Salamanca M, Mattei D, Salvoro C, Mazzotta G, De Pittà C, Middleton M, Skene D, Montagnese S, Costa R.
PER3 gene polymorphisms have been associated with differences in human sleep-wake phenotypes, and sensitivity to light. The aims of this study were to assess: i) the frequency of allelic variants at two PER3 polymorphic sites (rs57875989 length polymorphism: PER34, PER35; rs228697 SNP: PER3C, PER3G) in relation to sleep-wake timing; ii) the effect of morning light on behavioural/circadian variables in PER34/PER34 and PER35/PER35 homozygotes. 786 Caucasian subjects living in Northern Italy donated buccal DNA and completed diurnal preference, sleep quality/timing and sleepiness/mood questionnaires. 19 PER34/PER34 and 11 PER35/PER35 homozygotes underwent morning light administration, whilst monitoring sleep-wake patterns and the urinary 6-sulphatoxymelatonin (aMT6s) rhythm. No significant relationship was observed between the length polymorphism and diurnal preference. By contrast, a significant association was observed between the PER3G variant and morningness (OR = 2.10), and between the PER3G–PER34 haplotype and morningness (OR = 2.19), for which a mechanistic hypothesis is suggested. No significant differences were observed in sleep timing/aMT6s rhythms between PER35/PER35and PER34/PER34 subjects at baseline. After light administration, PER34/PER34 subjects advanced their aMT6s acrophase (p < 0.05), and showed a trend of advanced sleep-wake timing. In conclusion, significant associations were observed between PER3 polymorphic variants/their combinations and both diurnal preference and the response to light.