Circadian and other natural clock-like endogenous rhythms may have evolved to anticipate regular temporal changes in the environment. We report that a mutation in the circadian clock gene timeless in Drosophila melanogaster has arisen and spread by natural selection relatively recently in Europe. We found that, when introduced into different genetic backgrounds, natural and artificial alleles of the timeless gene affect the incidence of diapause in response to changes in light and temperature. The natural mutant allele alters an important life history trait that may enhance the fly's adaptation to seasonal conditions.

RGS2 (regulators of G-protein signaling) is a negative regulator of Galphaq protein signaling, which mediates the action of several vasoconstrictors. RGS2-deficient mouse line exhibits a hypertensive phenotype and a prolonged response to vasoconstrictors. To compare RGS2 expression in peripheral blood mononuclear cells (PBMs) and cultured fibroblasts from normotensive subjects and hypertensive patients. PBMs were isolated from 100 controls and 150 essential hypertensives. Additionally, fibroblasts were isolated from skin biopsy of 11 normotensives and 12 hypertensives and cultured up to the third passage. Quantitative mRNA and protein RGS2 expression were performed by real-time quantitative reverse transcriptase-polymerase chain reaction and by immunoblotting, respectively. Free Ca measurement was performed in monolayers of 24-h serum-deprived cells, using FURA-2 AM. Phosphorylation of the extracellular signal-regulated kinases ERK1/2 was measured by immunoblotting. Polymorphism (C1114G) in the 3' untranslated region of the RGS2 gene was investigated by direct sequencing and real-time polymerase chain reaction (PCR). RGS2 mRNA expression was significantly lower in PBM and in fibroblasts from hypertensives, in comparison to normotensives. C1114G polymorphism was associated with RGS2 expression, with the lowest values in GG hypertensives. The 1114G allele frequency was increased in hypertensives compared with normotensives. Angiotensin II-stimulated intracellular Ca increase and ERK1/2 phosphorylation were higher in fibroblasts from hypertensive patients compared with control subjects, and in those with the G allele, independently of the blood pressure status. The angiotensin II-stimulated Ca mobilization and ERK1/2 phosphorylation were negatively correlated with RGS2 mRNA expression. Low expression of RGS2 contributes to increased G-protein-coupled signaling in hypertensive patients. The allele G is associated with low RGS2 expression and blood pressure increase in humans.

Dysfunction of the circadian clock and single polymorphisms of some circadian genes have been linked to cancer susceptibility, although data are scarce and findings inconsistent. We aimed to investigate the association between circadian pathway genetic variation and risk of developing common cancers based on the findings of genome-wide association studies (GWASs). Single nucleotide polymorphisms (SNPs) of 17 circadian genes reported by three GWAS meta-analyses dedicated to breast (Discovery, Biology, and Risk of Inherited Variants in Breast Cancer (DRIVE) Consortium; cases, n = 15,748; controls, n = 18,084), prostate (Elucidating Loci Involved in Prostate Cancer Susceptibility (ELLIPSE) Consortium; cases, n = 14,160; controls, n = 12,724) and lung carcinoma (Transdisciplinary Research In Cancer of the Lung (TRICL) Consortium; cases, n = 12,160; controls, n = 16,838) in patients of European ancestry were utilized to perform pathway analysis by means of the adaptive rank truncated product (ARTP) method. Data were also available for the following subgroups: estrogen receptor negative breast cancer, aggressive prostate cancer, squamous lung carcinoma and lung adenocarcinoma. We found a highly significant statistical association between circadian pathway genetic variation and the risk of breast (pathway P value = 1.9 × 10^–6; top gene RORA, gene P value = 0.0003), prostate (pathway P value = 4.1 × 10^–6; top gene ARNTL, gene P value = 0.0002) and lung cancer (pathway P value = 6.9 × 10^–7; top gene RORA, gene P value = 2.0 × 10^–6), as well as all their subgroups. Out of 17 genes investigated, 15 were found to be significantly associated with the risk of cancer: four genes were shared by all three malignancies (ARNTL, CLOCK, RORA and RORB), two by breast and lung cancer (CRY1 and CRY2) and three by prostate and lung cancer (NPAS2, NR1D1 and PER3), whereas four genes were specific for lung cancer (ARNTL2, CSNK1E, NR1D2 and PER2) and two for breast cancer (PER1, RORC). Our findings, based on the largest series ever utilized for ARTP-based gene and pathway analysis, support the hypothesis that circadian pathway genetic variation is involved in cancer predisposition.

BACKGROUND: The number of studies on the association between clock genes’ polymorphisms and cancer susceptibility has increased over the last years but the results are often conflicting and no comprehensive overview and quantitative summary of the evidence in this field is available.