Linkage analysis of 2q14-q23 and 5q32 with blood pressure quantitative traits in Chinese sib pairs

Genetic biomarkers of hypertension and future challenges integrating epigenomics

Essential hypertension is a multifactorial disease, considered to be one of the world's greatest public health problems. Despite recent, major, technical advances aiming to elucidate its genetic component, the discovered biomarkers up to now were reported to have only small effects, explaining consequently a tiny fraction of its phenotypic variance and resulting in a large proportion of missing heritability. Likewise, little evidence is available with regard to the epigenetic regulation of essential hypertension, since no robust biomarkers have yet been reported. In the current review, we discuss the main approaches used exclusively to study the genetics and epigenetics of essential hypertension, the biomarkers identified, their clinical utility and the difficulties to be overcome. Furthermore, we propose a new category of functional genetic-epigenetic biomarkers, eMethSNPs, and we provide their hypothetical gene expression profiles for a genetic functional regulation of hypertension via DNA methylation. Though believed to be infrequent, eMethSNPs could constitute a new category of mechanistically-based genetic biomarkers predisposing to essential hypertension.

Appropriate Use of Information on Family History of Disease in Recruitment for Linkage Analysis Studies

When conducting genetic studies for complex traits, large samples are commonly required to detect any of the number of genes with relatively low effect thought to underly such traits. This is because, in contrast to monogenic diseases, complex traits typically result from a number of different genetic pathways (genetic heterogeneity) and any sample is likely to contain a considerable fraction of sporadic cases (phenocopies). Such samples are time-consuming and costly to recruit and analyse. Methods which might be used to decrease sample size include attempting to select families, with the aim of reducing genetic heterogeneity or phenocopy rate within the sample. Selecting cases with positive family history of disease should reduce the phenocopy rate, and this strategy has been employed in linkage studies of complex disease, although evaluations of such a strategy have been equivocal. This paper shows how identity by descent (IBD) distributions may be calculated for affected relative pairs recruited conditional on the affection status of a third relative. These distributions are then used to calculate expected power in affected sib and half-sib linkage studies when recruitment is conditional on family history of disease. We consider the proxy conditions of recruitment conditional on disease in an affected parent or third sibling with single-locus and additive multilocus genetic models. We show that while such selection strategies can reduce power if disease risk alleles are common and environmental heterogeneity low, under models more likely to underly common complex diseases power will generally be increased, and that this effect is greater as more loci are involved. Though the proxy cases studied are more extreme than a general strategy of asking potential recruits whether they have any family history of disease, these results suggest that conditional recruitment is more generally useful than previous studies have suggested.

Analysis of phenotype-genotype connection: the story of dissecting disease pathogenesis in genomic era in China, and beyond

DNA is the ultimate depository of biological complexity. Thus, in order to understand life and gain insights into disease pathogenesis, genetic information embedded in the sequence of DNA base pairs comprising chromosomes should be deciphered. The stories of investigating the association between phenotype and genotype in China and other countries further demonstrate that genomics can serve as a probe for disease biology. We now know that in Mendelian disorders, one gene is not only a dictator of one phenotype but also a dictator of two or more distinct disorders. Dissecting genetic abnormalities of complex diseases, including diabetes, hypertension, mental diseases, coronary heart disease and cancer, may unravel the complicated networks and crosstalks, and help to simplify the complexity of the disease. The transcriptome and proteomic analysis for medicine not only deepen our understanding of disease pathogenesis, but also provide novel diagnostic and therapeutic strategies. Taken together, genomic research offers a new opportunity for determining how diseases occur, by taking advantage of experiments of nature and a growing array of sophisticated research tools to identify the molecular abnormalities underlying disease processes. We should be ready for the advent of genomic medicine, and put the genome into the doctors' bag, so that we can help patients to conquer diseases.

Linkage analysis of chromosome 1 with essential hypertension and blood pressure quantitative traits in Chinese families

Summary Several recent studies have linked human chromosome 1p to essential hypertension (EH) or blood pressure (BP) levels. In an independent population of 148 hypertensive families from China we tested these findings. Thirty highly informative microsatellite markers spanning about 284 cM were genotyped. Qualitative linkage analysis was conducted using non-parametric linkage analysis implemented within the GENEHUNTER 2.0 software, whereas quantitative analysis was performed with the variance-component method integrated in the S.O.L.A.R. 1.7.4. software with an additional Haseman-Elston method using the SAGE/SIBPAL2 program. We observed suggestive linkage between D1S2890 (1p31, 80.9 cM) and hypertension using the multipoint non-parametric linkage analysis (NPL = 2.19, P = 0.01). In the quantitative analysis we didn't observe a significant excess of identity-by-descent allele sharing between the systolic blood pressure levels and the markers. However, the D1S207 microsatellite marker (1p21) which is located about 107 cM from the telomere of 1p showed weak linkage evidence with the diastolic blood pressure levels (LOD = 1.42). These findings suggest linkage of 1p31 with essential hypertension in the ethnic Chinese, and provide a potential clue for future studies involving candidate genes for hypertension.

Haplotypic analyses of the aldosterone synthase gene CYP11B2 associated with stage-2 hypertension in northern Han Chinese

The objective of this study was to investigate the association of polymorphisms in the aldosterone synthase gene CYP11B2 (-344T/C, Lys173/Arg, and an intronic conversion [IC]) with stage-2 hypertension in northern Han Chinese. A total of 503 hypertensives and their age-, gender-, and area-matched controls were included in this study. The female hypertensives had significantly higher frequencies of the -344T, 173Lys, and IC-conversion alleles (p = 0.002, 0.002, and 0.014, respectively). The estimated frequency of haplotype composed of the -344T, 173Lys, and IC-conversion alleles (haplotype 4) was significantly higher in the female hypertensives compared with their controls (p = 0.007). Using a multivariate score test, we found that haplotype 4 remained associated with female hypertension after the adjustment for covariates (p = 0.003), while the haplotype 3 of T-Arg-WT showed a protective effect both in the males and in the females (p = 0.03 and 0.006, respectively). The odds ratio for haplotype phase of 4-4 was 2.60 (95% CI, 1.21-5.58) and for 3-3, 0.20 (95% CI, 0.03-0.77). These results indicate that the Lys173 and the IC-conversion allele of the CYP11B2 gene confer an increased risk for stage-2 hypertension in northern Han Chinese women.

Genetic susceptibility loci for essential hypertension and blood pressure on chromosome 17 in 147 Chinese pedigrees

OBJECTIVES

We scanned human chromosome 17 to verify previous studies on the chromosome as well as to explore possible new loci of essential hypertension in a Chinese Han population.

METHODS

A genomic scan of chromosome 17 with 15 microsatellite markers was conducted in a total of 757 individuals from 147 Chinese hypertension pedigrees. We used three softwares to analyse hypertension as a qualitative trait and blood pressure as quantitative phenotypes linkage analyses in the North group (406 individuals from 78 northern families), the South group (351 individuals from 69 southern families) and the combined group of the Chinese population separately.

RESULTS

For qualitative trait, a 7-cM (centiMorgan) interval flanked by D17S831 (7 cM) and D17S938 (15 cM) showed suggestive linkage results (P < 0.00074) in the southern population by SAGE/SIBPAL2. For blood pressure (BP) quantitative phenotypes, the regions with lowest P values in SAGE and highest logarithm of odds (LOD) scores in SOLAR just overlapped this 7-cM interval in the South group for both systolic blood pressure (SBP) and diastolic blood pressure (DBP), though these peaks did not yet reach to the suggestive linkage criteria (P = 0.00074, LOD score = 2.2). In the northern population, in a region around 75.0 cM (D17S787) a peak was found with non-parametric-linkage (NPL) score 1.82 for qualitative trait using GENEHUNTER.

CONCLUSIONS

In the southern population of China, our results demonstrate that a 7-cM interval region flanked by D17S831 (7 cM) and D17S938 (15 cM) is suggestively linked with hypertension.

Human genome research in China

Significant progress in human genome research has been made in China since 1994. This review aims to give a brief and incomplete introduction to the major research institutions and their achievements in human genome sequencing and functional genomics in medicine, with emphasis on the "1% Sequencing Project", the generation of single nucleotide polymorphism and haplotype maps of the human genome, disease gene identification, and the molecular characterization of leukemia and other diseases. Chinese efforts towards the sequencing of pathogenic microbial genomes and of the rice (Oryza sativa ssp. Indica) genome are also described.