Identification Of Novel Genetic Association Between GGT7 And LINC00944 And Hypertension In Chinese Han Population

Hypertension is the leading risk factor for the global burden of disease and globalmortality.In China,there are more than 200 million people suffering from hypertension.As hypertension greatly increases the risk of cardiovascular diseases,it has become a major public health problem that can not be ignored.Genetic factors play an important role in the pathogenesis of hypertension.Multiple genes and genetic variants have been found to be associated with the risk of hypertension or the quantitative blood pressure trait.Different ethnic populations share some common genetic factors.However,some genetic variants show population-specific genetic heterogeneity,and increase the risk of hypertension only in some specific populations.In order to identify new genetic variants associated with hypertension in the Chinese population,we carried out a three-phase genome-wide association study（GWAS）for hypertension in the Chinese Han population.First,genome-wide single nucleotide polymorphisms（SNPs）genotyping was performed for the first phase discovery population of 353 hypetension cases and 332 non-hypertension controls,followed by genotype imputation and principal component analyses.A total of 3,956,088 SNPs were identified and analyzed for their association with hypertension using logistic regression and adjusted for the age,age^²,gender,and the first three principal components.A total of 17,435 SNPs showed a P value of<5.0×10^-3 and studied further.The second phase replication study was carried out to reduce false positives,and the 17,435 SNPs were further tested in the replication population with 1,592 cases and1,302 controls for their association with hypertension.Among them,136 SNPs located at15 independent loci were showed a P value of<5.0×10^-3.Finally,in the third validation phase study,lead SNPs in the 15 independent loci were genotyped in the third validation population（3,274 cases and 2,734 controls）,and two SNPs,including rs2064453 and rs10847208,were found to be significantly associated with hypertension.In all of populations combined,rs2064453 showed a significant P_meta of 3.5×10^-7（Odds Ratio=1.17）,and rs10847208 showed a significant P_meta of 1.3×10^-7（Odds Ratio=1.27）.These results identify two novel genetic loci,represented by SNPs rs2064453 and rs10847208,for hypertension.SNP rs2064453 is located on chromosome 20q11 and in a region marked by a DNase hypersensitivity peak cluster in the promoter region of the GGT7 gene encoding gamma-glutamyltransferase 7.Analysis of expression quantitative trait loci（e QTLs）in blood leucocytes from 309 Chinese study subjects revealed that the TT and TC genotypes of rs2064453 showed a significantly higher expression level of GGT7 than the CC genotypes.In addition,GGT7 promoter luciferase reporter gene assays showed that the risk allele T can significantly increase the transcriptional activity of the GGT7 promoter compared with the C allele.Moreover,endothelial cells treated with purified GGT7 showed a significantly reduced level of phosphorylated ERK1/2,which was involved in the pathogenesis of hypertension.Furthermore,knockdown of GGT7 expression significantly increased the expression level of PPP6C encoding the catalytic subunit of phosphoprotein phosphatase 6,which was also involved in the pathogenesis of hypertension.These results show that GGT7SNP rs2064453 increases the risk of hypertension by reducing the activity of ERK1/2 and increasing the expression of PPP6C.Our study also identified significant association between variant rs10847208 and hypertension.SNP rs10847208 is located on chromosome 12q24 and located in the two non-coding RNA genes LINC00944 and LINC00943 with opposite transcription direction,and in the last exon of LINC00944.However,the function of LINC00944 or LINC00943 is currently unclear,and therefore,the molecular mechanism of how SNP rs10847208increases the risk of hypertension needs further research.In summary,this study identified two novel loci for hypertension,represented by SNP rs2064453 in the promoter of GGT7 and SNP rs10847208 in lnc RNA genes LINC00943/LINC00944.Our data enriched the genetic structure of hypertension in the Chinese population.In addition,the study also found that the risk allele T of rs2064453increase risk of hypertension by increasing the expression of GGT7,which leads to reduced ERK1/2 activation and increased expression of PPP6C,resulting in the development of hypertension.The findings suggest that GGT7 is a novel susceptibility gene for hypternsion,provide an interesting target gene for further investigation of novel molecular pathogenic mechanisms of hypertension,and for developing treatments for hypertension.