As a nonmutagenic human carcinogen, arsenic (As)'s carcinogenic activity is likely the result of epigenetic changes, particularly alterations in DNA methylation. While increasing studies indicate a potentially important role for timing of As exposure on DNA methylation patterns and the subsequent differential risks for As toxicity and carcinogenesis, there is a lack of research that tackles these critical questions, particularly in human based populations. Here we reported a family-based study including three generations, in which each generation living in the same household had a distinctive timing of As exposure: in adulthood, in utero and during early childhood, and in germlines exposure for grandparents, parents, and grandchildren, respectively. We generated genome-wide DNA methylation data for 18 As-exposed families, nine control families, as well as 18 arsenical skin lesion patients. Our analysis showed that As exposure may leave detectable DNA methylation changes even though exposure occurred decades ago, and the most significant changes of global DNA methylation were observed among patients afflicted with arsenical skin lesions. As exposure across generations shared common differentially methylated DNA loci and regions (744 DML and 15 DMRs) despite the distinctive exposure timing in each generation. Importantly, based on these DML, clustering analysis grouped skin lesion patients together with grandparents in exposed families in the same cluster, separated from grandparents in control families. Further analysis identified a number of DML and several molecular pathways that were significantly distinguished between controls, exposed populations, as well as skin lesion patients. Finally, our exploratory analysis suggested that some of these DML altered by As exposure, may have the potential to be inherited affecting not only those directly exposed but also later generations. Together, our results suggest that common DML and/or DMRs associated with an increased risk for disease development could be identified regardless of when exposure to As occurred during their life span, and thus may be able to serve as biomarkers for identifying individuals at risk for As-induced skin lesions and possible cancers.

ABSTRACT. Abnormalities in renal sodium chloride and water reabsorption play important roles in the development of hypertension. Mutations in the genes involved in renal sodium chloride reabsorption can affect blood pressure. Recently, the R904Q variant of the sodium/ chloride transporters, member 3 (SLC12A3) gene and the T481S variant of the chloride channel Kb (ClC-Kb) gene were found to be implicated in essential hypertension. We investigated a possible role of the SLC12A3 and ClC-Kb genes in the prevalence of essential hypertension in the Mongolian and Han ethnic groups. The study population comprised 308 unrelated Mongolians with essential hypertension, 271 Mongolian normotensives, 285 unrelated Han with essential hypertension, and 194 Han normotensives living in Inner Mongolia. The presence of the SLC12A3 R904Q and ClC-Kb-T481S polymorphisms was determined using TaqMan PCR. The risk factors for hypertension were age, body Renal salt reabsorption-related gene and hypertension mass index, alcohol consumption, total plasma cholesterol, and lowdensity lipoprotein cholesterol. The genotype and allele frequencies of SLC12A3 R904Q and ClC-Kb-T481S were not significantly different between hypertensive patients and controls in the Mongolian (SLC12A3 R904Q, P = 0.471 and P = 0.494, ClC-Kb-T481S, P = 0.960 and P = 0.960, respectively) and Han (SLC12A3 R904Q, P = 0.765 and P = 0.777, ClCKb-T481S, P = 0.100 and P = 0.103, respectively) populations. There was no significant association between the SLC12A3 R904Q variant and the ClC-Kb-T481S variant and essential hypertension in either ethnic group.

Genetic variation is thought to contribute to the etiology of hypertension, and E-selectin is a candidate essential hypertension-associated gene. Objective In this study, we attempted to test the hypothesis that subtle haplotype variants of SELE genes may be sources of essential hypertension in Mongolian and Han populations. Materials A total of 429 unrelated Mongolian herdsmen and 416 Han farmers were enrolled, including 212 Mongolian essential hypertension (EH) patients, 217 Mongolian normotensives (controls), 200 Han EH patients and 216 Han normotensives (controls). Methods All nine tag single-nucleotide polymorphisms (SNPs) within the SELE gene were retrieved from HapMap and the genotyping was performed using a polymerase chain reaction (PCR)/ligase detection reaction assay. Results The distributions of the A-allele frequency of rs3917458 and the C-allele frequency of rs2179172 differed significantly between the hypertensive subjects and controls in the Han population. The frequency of haplotype GGC was significantly higher in the EH group than in the controls in the Mongolian population. In the Han population, a significant difference was observed in the haplotype frequency of TCC between the patients and controls, whereas haplotype ACA was detected significantly less often in the EH subjects than in the controls. Conclusion Meanwhile, the haplotype TCC in the Han hypertensive patients and the haplotype GGC in the Mongolian patients had independent effects in increasing the risk for EH and maybe used as risk factors for predicting high blood pressure. However, the haplotype ACA had an independent effect in decreasing the risk of hypertension and may be protective in normotensive subjects in the Han population. Therefore, multiple SNPs in combination in SELE may confer a risk of hypertension.

We investigated a possible association between genetic variations in chloride channel Kb (CLCNKB) gene and essential hypertension (EH) in the Mongolian and Han populations in Inner Mongolia. Our study included 414 unrelated Mongolian herdsmen and 524 Han farmers. Two tagSNPs of CLCNKB (rs945393 and rs10803414) were identified from the Chinese HapMap database based on pairwise r(2) ≥ 0.5 and minor allele frequency ≥0.05. Genotyping was performed using the PCR/ligase detection reaction assay. There was significant difference in allele frequency of rs10803414 between the EH group (35%) and the control group (26%) in the Mongolian population (P < .05). Significant association was identified between rs10803414 and EH in the Mongolian population (P < .05) and rs945393 and EH in the Han population (P < .01). The frequency of haplotype CC in the EH group (9.4%) was significantly higher than in the control group (4.6%) in the Mongolian population; individuals who possessed the CC haplotype had a significantly higher risk of EH in the Mongolian population. There was no association between haplotype and EH in the Han population. After adjusting for age, sex, and other confounding risk factors, only rs10803414 was the risk factor of hypertension in Mongolians. Our results indicate that rs10803414 in CLCNKB confers a significant risk of EH in the Mongolian population and haplotype CC of CLCNKB is a genetic factor for EH in the Mongolian population. Our study expands the association between CLCNKB and EH to a non-European ancestry population and provides the first evidence of a cross-race susceptibility of EH locus.

Aldosterone synthase (CYP11B2) and α-adducing (ADD1) are candidate genes that play key roles during essential hypertension (EH) incidence. However, the association between their genetic mutations and the risk of EH is unclear. The present study investigated specific single nucleotide polymorphisms (SNPs) from CYP11B2 and ADD1, and their potential role as risk factors for EH based on 423 Mongolian and 410 Han people in Inner Mongolia province. In the allelic model, people with ADD1 rs2239728-A presented a 0.74-fold risk than rs2239728-C, whereas the ADD1 rs4961-T was associated with a 1.37-fold higher risk than allele G in the Han population. The genetic model reported that the rs2239728-A carrier (AA + AC) was 0.59-fold lower than the CC carrier, whereas the rs4961-G carrier (GG + GT) was 0.59-fold lower than the TT carrier in the dominant model. After gender adjustment, people with rs2239728-A was a 0.63-fold risk than –C in EH, but the rs4961-T carrier was associated with a 1.63-times higher risk than –G in females. Haplotype analysis showed that GCCT was associated with essential hypertension in the Han population, and it was a risk factor for EH. Our identification reported novel SNPs of ADD1 with protective significance for EH among females in the Chinese Han population, together with its haplotype GCCT as a risk factor for EH.