Different roles of two novel susceptibility loci for nonsyndromic orofacial clefts in a Chinese Han population

Nonsyndromic orofacial clefts (NSOC) are the most common developmental anomalies in human beings. Recently, a large-scale genome-wide association study identified two novel NSOC susceptibility loci: rs13041247 near MAFB and rs560426 near ABCA4. In the present study, we recruited 396 NSOC cases and 384 healthy controls to replicate their associations with risk of NSOC as well as their subgroups in a Chinese Han population. We found the overall genotype and allele frequencies of rs13041247, but not rs560426 were significantly different between cases and controls. Further logistic regression analysis showed rs13041247 CT, CC, and CT/CC were associated with decreased NSOC susceptibility, compared with rs13041247 TT wide-type homozygote. Moreover, the apparent protection against cleft lip with or without cleft palate (CL/P), cleft lip with cleft palate (CLP), and cleft lip only (CLO) was also identified in stratified analysis. However, none of any rs560426 genotypes or alleles was associated with risk of NSOC or their subgroups. Taken together, our findings confirmed the contribution of MAFB in the etiology of NSOC in a Chinese Han population.     

Polymorphisms of genes involved in inflammation and blood vessel development influence the risk of varicose veins

Heredity plays an important role in the etiology of varicose veins (VVs). However, the genetic basis underlying this condition remains poorly understood. Our aim was to replicate top association signals from genome‐wide association studies (GWASs) for VVs of lower extremities using 2 independent datasets—our sample of ethnic Russian individuals (709 cases and 278 controls) and a large cohort of British residents from UK Biobank (10 861 cases and 397 594 controls). Associations of polymorphisms rs11121615, rs6712038, rs507666, rs966562, rs7111987, rs6062618, and rs6905288 were validated in the UK Biobank individuals at a Bonferroni‐corrected significance level. In Russian cohort, only rs11121615 reached a nominal significance level of P < .05. Results of original GWAS and replication studies were combined by a meta‐analysis, and polymorphisms listed above as well as rs111434909 and rs4463578 passed a genome‐wide significant threshold. Notably, the majority of these polymorphisms were located within or near genes involved in vascular development and remodeling, and regulation of inflammatory response. Our results confirm the role of these polymorphisms in genetic susceptibility to VVs and indicate the revealed genomic regions as good candidates for further fine‐mapping studies and functional analysis. Moreover, our findings implicate inflammation and abnormal vascular architecture in VVs pathogenesis.     

Investigation of the CACNA1A gene as a candidate for typical migraine susceptibility

Typical migraine is a complex neurological disorder comprised of two main subtypes: migraine with (MA) and without aura (MO). The disease etiology is still unclear, but family studies provide strong evidence that defective genes play an important role. Familial hemiplegic migraine (FHM) is a very rare and severe subtype of MA. It has been proposed that FHM and MA may have a similar genetic etiology. Therefore, genetic studies on FHM provide a useful model for investigating the more prevalent types of typical migraine. FHM in some families has been shown to be caused by mutations in a brain‐specific P/Q‐type calcium channel α1 subunit gene (CACNA1A) on chromosome 19p13. There has also been a report of a CACNA1A mutation being associated with MA in a patient from a family with predominant FHM. We have previously demonstrated suggestive linkage of typical migraine in a large Australian family to the FHM region on chromosome 19p13. These findings suggest that CACNA1A may also be implicated in the etiology of typical migraine in this pedigree. To investigate this possibility, we sequenced two patients carrying the critical susceptibility haplotype surrounding CACNA1A. No disease‐causing mutations or polymorphisms were revealed in any of the 47 exons screened. To determine whether the CACNA1A gene was implicated in typical migraine susceptibility in the general Caucasian population, we also analyzed 82 independent pedigrees and a large case control group. We did not detect any linkage or association in these groups and conclude that if CACNA1A plays a role in typical migraine, it does not confer a major effect on the disease. © 2001 Wiley‐Liss, Inc.     

11q13 is a susceptibility locus for hormone receptor positive breast cancer

A recent two-stage genome-wide association study (GWAS) identified five novel breast cancer susceptibility loci on chromosomes 9, 10, and 11. To provide more reliable estimates of the relative risk associated with these loci and investigate possible heterogeneity by subtype of breast cancer, we genotyped the variants rs2380205, rs1011970, rs704010, rs614367, and rs10995190 in 39 studies from the Breast Cancer Association Consortium (BCAC), involving 49,608 cases and 48,772 controls of predominantly European ancestry. Four of the variants showed clear evidence of association (P ≤ 3 × 10(-9) ) and weak evidence was observed for rs2380205 (P = 0.06). The strongest evidence was obtained for rs614367, located on 11q13 (per-allele odds ratio 1.21, P = 4 × 10(-39) ). The association for rs614367 was specific to estrogen receptor (ER)-positive disease and strongest for ER plus progesterone receptor (PR)-positive breast cancer, whereas the associations for the other three loci did not differ by tumor subtype.     

Genome‐wide compound heterozygosity analysis highlighted 4 novel susceptibility loci for congenital heart disease in Chinese population

Genome‐wide association studies (GWASs) have achieved great success in deciphering the genetic cause of congenital heart disease (CHD). However, the heritability of CHD remains to be clarified, and numerous genetic factors responsible for occurrence of CHD are yet unclear. In this study, we performed a genome‐wide search for relaxed forms of compound heterozygosity (CH) in association with CHD using our existing GWAS data including 2265 individuals (957 CHD cases and 1308 controls). CollapsABEL was used to iteratively test the association between the CH genotype and the CHD phenotype in a sliding window manner. We highlighted 17 genetic loci showing suggestive CH‐like associations with CHD (P < 5 × 10^?8), among which 4 genetic loci had expression quantitative trait loci (eQTL) effects in blood (P_eQTL < 0.01). After conditional association analysis, each loci had only 1 independently effective signal reaching the significance threshold (rs2071477/rs3129299 at 6p21.32, P = 2.47 × 10^?10; rs10773097/rs2880921 at 12q24.31, P = 3.30 × 10^?8; rs73032040/rs7259476 at 19q13.11, P = 1.14 × 10^?8; rs10416386/rs4239517 at 19q13.31, P = 1.15 × 10^?9), together explained 7.83% of the CHD variance. Among these 4 associated loci, outstanding candidates for CHD‐associated genes included UBC, CFM2, ZNF302, LYPD3 and CADM4. Although replication studies with larger sample size are warranted, the first CH GWAS of CHD may extend our current knowledge of the genetic contributions to CHD in the Han Chinese population.     

Genotyping of three candidate genes after whole-genome preamplification of DNA collected from buccal cells

The amount of genomic DNA obtained from buccal cell methods may be suboptimal for large-scale genetics projects, because the quantity of DNA may be insufficient for the number of analyses proposed. Primer extension preamplification (PEP) methods that can amplify the entire genome 100-fold or more, offer a potential solution to this problem. We compared PEP buccal DNA with genomic buccal DNA from 315 individuals from 97 families of the Colorado Longitudinal Twin Study for three loci: the dopamine transporter, dopamine D4 receptor, and serotonin transporter. A total of 1890 genomic and 1890 PEP alleles were assessed, and 1670 comparisons (88%) agreed after a single determination. Fifty-three individuals had one or more failed initial polymerase chain reactions (PCR), with 81 failed PCRs in total, accounting for 162 missing allele calls. The failed PCRs were repeated once, and 146 of the missing allele calls were recovered. Comparisons between genomic and PEP DNA allele calls showed 37 individuals had one or more discrepancies, for a total of 52 inconsistencies. Of these, the initial PEP result was found to be correct in 18 cases, the initial genomic result was found to be correct in 25 cases, and 9 could not be resolved. Overall, rates of true calls, missing data, and genotyping errors for genomic and PEP DNA samples were nearly identical: of the 1890 genotypes assessed, true calls were found in 1845 genomic and 1840 PEP samples, missing genotypes in 18 genomic and 16 PEP samples, and incorrect assignments in 18 genomic and 25 PEP samples. These results suggest that routine whole-genome preamplification of genomic DNA is an appropriate method for providing DNA to genotype these loci.     

Genetic variations as cancer prognostic markers: review and update

Cancer molecular epidemiology traditionally studies the relationship between genetic variations and cancer risk. However, recent studies have also focused on disease outcomes. The application and design of disease outcome studies have been an extension of disease risk assessment. Yet there are a number of unique considerations important in outcome assessments. We review how genetic approaches used for disease susceptibility, such as candidate gene and genome‐wide association study (GWAS) approaches, can be adapted carefully to systematically identify cancer prognostic and predictive alleles. We discuss the interrelatedness among the disease susceptibility, treatment response, and prognosis at the genetic level and focus on how the emerging technologies and approaches can uniquely benefit the genetic prognosis studies. Hum Mutat 30:1–9, 2009. © 2009 Wiley‐Liss, Inc.     

GENOMIZER: an integrated analysis system for genome-wide association data

Genome-wide association analysis appears to be a promising way to identify heritable susceptibility factors for complex human disorders. However, the feasibility of large-scale genotyping experiments is currently limited by an incomplete marker coverage of the genome, a restricted understanding of the functional role of given genomic regions, and the small sample sizes used. Thus, genome-wide association analysis will be a screening tool to facilitate subsequent gene discovery rather than a means to completely resolve individual genetic risk profiles. The validation of association findings will continue to rely upon the replication of "leads" in independent samples from either the same or different populations. Even under such pragmatic conditions, the timely analysis of the large data sets in question poses serious technical challenges. We have therefore developed public-domain software, GENOMIZER, that implements the workflow of an association experiment, including data management, single-point and haplotype analysis, "lead" definition, and data visualization. GENOMIZER (www.ikmb.uni-kiel.de/genomizer) comes with a complete user manual, and is open-source software licensed under the GNU Lesser General Public License. We suggest that the use of this software will facilitate the handling and interpretation of the currently emerging genome-wide association data.     

人类传染性疾病的遗传易感性

双生子、寄养子、家系和基于群体的关联研究表明机体遗传因素在决定人类传染性疾病的易感性中起着极为重要的作用。除少数基因已被揭示与疟疾和艾滋病的遗传易感性强烈相关外,还有其它大量基因显示与结核病、麻疯病和慢性乙型肝炎等传染性疾病的易感性相关。一些免疫相关基因可能在介导传染性疾病的遗传易感机制中担负重要角色。上述研究大多表明,绝大多数常见传染性疾病属于典型的多基因疾病(复杂性状),是致病微生物和宿主之间在长期的进化过程中交互作用的结果。后基因组时代人类基因组学的快速发展必然大大加速传染病遗传易感基因的鉴定,这有助于今后研发针对这些疾病的新的预防和治疗策略。但是,这一领域仍然面临着诸多需要克服的困难。     

Comparison of genetic variation of breast cancer susceptibility genes in Chinese and German populations

Genome-wide association studies (GWAS) identified several genetic risk factors for breast cancer, however, most of them were validated among women of European ancestry. This study examined single-nucleotide polymorphisms (SNPs) contributing to breast cancer in Chinese (984 cases and 2206 controls) and German (311 cases and 960 controls) populations. Eighteen SNPs significantly associated with breast cancer, previously identified in GWAS were genotyped. Twelve SNPs passed quality control and were subjected to statistical analysis. Seven SNPs were confirmed to be significantly associated with breast cancer in the Chinese population, reflecting three independent loci (ESR1, FGFR2, TOX3) and five of these were also confirmed in the German population. The strongest association was identified for rs2046210 in the Chinese (odds ratio (OR)=1.42, 95% confidence interval (CI)=1.28–1.59, P=1.9 × 10⁻¹⁰) and rs3803662 in the German population (OR=1.43, 95% CI=1.17–1.74, P=4.01 × 10⁻⁴), located upstream of the ESR1 and TOX3 gene, respectively. For the first time, rs3757318 at 6q25.1, located next to the gene encoding estrogen receptor α (ESR1) was found to be strongly associated with breast cancer (OR=1.33, 95% CI=1.18–1.49, P=1.94 × 10⁻⁶) in the Chinese population. The frequency of this variant was markedly lower in the German population and the association was not significant. Despite the genetic differences, essentially the same risk loci were identified in the Chinese and the German populations. Our study suggested the existence of common genetic factors as well as disease susceptibility differences for breast cancer in both populations and highlighted the importance of performing comparison analyses for disease susceptibility within ethnic populations.     

Trans‐Ethnic Meta‐Analysis Identifies Common and Rare Variants Associated with Hepatocyte Growth Factor Levels in the Multi‐Ethnic Study of Atherosclerosis (MESA)

Hepatocyte growth factor (HGF) is a mesenchyme‐derived pleiotropic factor that regulates cell growth, motility, mitogenesis, and morphogenesis in a variety of cells, and increased serum levels of HGF have been linked to a number of clinical and subclinical cardiovascular disease phenotypes. However, little is currently known regarding which genetic factors influence HGF levels, despite evidence of substantial genetic contributions to HGF variation. Based upon ethnicity‐stratified single‐variant association analysis and trans‐ethnic meta‐analysis of 6201 participants of the Multi‐Ethnic Study of Atherosclerosis (MESA), we discovered five statistically significant common and low‐frequency variants: HGF missense polymorphism rs5745687 (p.E299K) as well as four variants (rs16844364, rs4690098, rs114303452, rs3748034) within or in proximity to HGFAC. We also identified two significant ethnicity‐specific gene‐level associations (A1BG in African Americans; FASN in Chinese Americans) based upon low‐frequency/rare variants, while meta‐analysis of gene‐level results identified a significant association for HGFAC. However, identified single‐variant associations explained modest proportions of the total trait variation and were not significantly associated with coronary artery calcium or coronary heart disease. Our findings indicate that genetic factors influencing circulating HGF levels may be complex and ethnically diverse.     

What can genetics tell us about the cause of fixed airflow obstruction?

Chronic obstructive pulmonary disease (COPD) is a major cause of chronic morbidity and mortality worldwide with smoking being the most important risk factor of the disease. However, lung function and COPD are known to also have a genetic component and a deeper knowledge of the genetic architecture of the disease could lead to further understanding of predisposition to COPD and also to development of new therapeutic interventions. Genetic linkage studies and candidate gene association studies have not provided evidence to convincingly identify the genes underlying lung function or COPD. However, recent large genome‐wide association studies (GWAS) including tens of thousands of individuals have identified 26 variants at different loci in the human genome that show robust association with quantitative lung function measures in the general population. A growing number of these variants are being shown to be associated with COPD. Following the identification of these new lung function loci, the challenge now lies in refining the signals to identify the causative variants underlying the association signals and relating these signals to the molecular pathways that underlie lung function.     

GWAS and network analysis of co‐occurring nicotine and alcohol dependence identifies significantly associated alleles and network

Alcohol dependence (AD) and nicotine dependence (ND) co‐occur frequently (AD+ND). We integrated SNP‐based, gene‐based, and protein–protein interaction network analyses to identify shared risk genes or gene subnetworks for AD+ND in African Americans (AAs, N = 2,094) and European Americans (EAs, N = 1,207). The DSM‐IV criterion counts for AD and ND were modeled as two dependent variables in a multivariate linear mixed model, and analyzed separately for the two populations. The most significant SNP was rs6579845 in EAs (p < 1.29 × 10^?8) in GM2A, which encodes GM2 ganglioside activator, and is a cis‐expression quantitative locus that affects GM2A expression in blood and brain tissues. However, this SNP was not replicated in our another small sample (N = 678). We identified a subnetwork of 24 genes that contributed to the AD+ND criterion counts. In the gene‐set analysis for the subnetwork in an independent sample, the Study of Addiction: Genetics and Environment project (predominately EAs), these 24 genes as a set differed in AD+ND versus control subjects in EAs (p = .041). Functional enrichment analysis for this subnetwork revealed that the gene enrichment involved primarily nerve growth factor pathways, and cocaine and amphetamine addiction. In conclusion, we identified a genome‐wide significant variant at GM2A and a gene subnetwork underlying the genetic trait of shared AD+ND. These results increase our understanding of the shared (pleiotropic) genetic risk that underlies AD+ND.     

The impact of epigenomic next‐generation sequencing approaches on our understanding of neuropsychiatric disorders

Patients suffering from psychiatric disorders have a life span burden, which represents an enormous human, family, social, and economical cost. Several concepts have revolutionized our way of appraising neuropsychiatric disorders (NPDs). They result from a combination of genetic factors and environmental insults, and their etiology finds roots in the neurodevelopmental period. As epigenetic mechanisms tightly control brain development, exposure to adverse conditions disturbing the epigenetic landscape of the fetal brain increases the risk of developing NPDs, due to the persistence of abnormal epigenetic signatures, at distance from the initial stimulus. Here, we review these concepts and discuss recent results based on next‐generation sequencing (NGS) approaches that have shed light on the mechanisms that underlie the emergence of NPDs, highlighting the importance of epigenetic phenomena. Because epigenetic mechanisms are potentially reversible, unraveling the epigenetic contribution to the etiology of NPDs is key to the design of future therapeutic strategies. Early diagnosis of patients prone to NPDs for early intervention represents a challenge that waits for biomarkers of vulnerability, and could be decisive for improving the outcome and prognosis of “at‐risk” patients.     

The Challenge for the Next Generation of Medical Geneticists

Next‐generation sequencing (NGS) has allowed a tremendous progress in the characterization of the molecular bases of genetic diseases and the last annual American Society of Human Genetics meeting has highlighted the implementation of whole exome sequencing in medical genetics. Several investigators suggest that it should be medically relevant for each individual to have the exome sequenced. These perspectives do not take into account the complexity of genetic variation interpretation and genetic determinism of human diseases: an important limiting step of targeted analyses of gene(s) involved in Mendelian diseases is already the interpretation of variants of unknown significance; most of the 20,000 single nucleotide variations present in each exome, even those having a very low allelic frequency, are not deleterious; the genetic determinism of the majority of human diseases involves either a combination of numerous genetic variations, each conferring a slightly increased risk, or rare genetic variations with a strong effect, but the demonstration of their involvement in diseases is particularly challenging. The challenge for the next generation of medical geneticists will be to integrate the technological power of NGS technologies, the complexity of genome interpretation, the importance of phenotyping before genotyping, and the guidelines of medical genetics raised in the pre‐NGS era.     

Refinement of the DFNA41 locus and candidate genes analysis

We previously mapped the 41^rst gene locus (DFNA41) for autosomal dominant hearing loss on chromosome 12q24-qter in a large multi-generational Chinese family. We determined that DFNA41 is located in a 15 cM region, proximal to the marker D12S1609. A maximum two point LOD score of 6.56 at =0.0 was obtained with marker D12S343. In the current study, screening of eight candidate genes within the DFNA41 interval did not reveal the mutation causing deafness in this family. Eight highly informative single nucleotide polymorphisms (SNPs) in the region of D12S343 were selected for linkage and association study. Because the pedigree studied here is a large family with many founders, we applied the transmission/disequilibrium (TDT) test. To account for the dependence of small families and the relatively small sample size, simulations were performed to obtain P-values. For three nearby SNPs spanning a 7 kb interval, we found significant evidence of linkage and association. The highest Z score of linkage and association of 3.6 (P0.0001) was obtained for SNP rs1566667. Haplotype analysis revealed that affected individuals were heterozygous for one core SNP (rs1027560–rs1027557–rs1566667–rs1463865–rs2078105) CAGTC haplotype, confirming location and autosomal dominant inheritance of the DFNA41 locus. Examination of pairwise LD calculation identified a major haplotype block defined by the four most centromeric SNPs. This study represents a significant refinement of the DFNA41 locus and should facilitate positional cloning of the disease gene.     

Association of polymorphisms in 9p21 region with CAD in North Indian population: replication of SNPs identified through GWAS

Kumar J, Yumnam S, Basu T, Ghosh A, Garg G, Karthikeyan G, Sengupta S. Association of polymorphisms in 9p21 region with CAD in North Indian population: replication of SNPs identified through GWAS. Coronary artery disease (CAD) is one of the leading causes of death worldwide that is influenced by both environmental as well as genetic factors. Several recent genome‐wide association studies (GWAS) have reported the association of multiple single nucleotide polymorphisms (SNPs) mainly in the 9p21 region with CAD. However, the association of these SNPs with CAD has not been rigorously tested in Indian population, which accounts for the largest incidences of CAD in the world. Herein, we genotyped six such SNPs (rs10116277, rs10757274, rs1333040, rs2383206, rs2383207 and rs1994016) identified through GWAS, in 754 individuals (311 angiography‐confirmed CAD patients and 443 treadmill test controls) recruited mainly from North India to evaluate if these SNPs were associated with CAD. The minor allele frequency of these six SNPs was comparable to that reported in the respective GWAS. We found that three of these SNPs (rs10116277, rs1333040 and rs2383206) present at the locus 9p21 were significantly associated with CAD even after controlling for the confounding factors such as age, sex, body mass index, homocysteine, hypertension, diabetes, smoking, diet, etc. In conclusion, the locus 9p21 found to be significantly associated with cardiovascular diseases in the Caucasian populations seems to be also important in North Indian population.