IGG3: a tool to rapidly integrate large genotype datasets for whole-genome imputation and individual-level meta-analysis.

SUMMARY: There is an urgent and increasing demand for integrating large genotype datasets across genome-wide association studies and HapMap project for whole-genome imputation and individual-level meta-analysis. A new algorithm was developed to efficiently merge raw genotypes across large datasets and implemented in the latest version of IGG, IGG3. In addition, IGG3 can integrate the latest phased and unphased HapMap genotypes and can flexibly generate complete sets of input files for six popular genotype imputation tools. We demonstrated the efficiency of IGG3 by simulation tests, which could rapidly merge genotypes in tens of thousands of large genotype chips (e.g. Affymetrix Genome-Wide Human SNP Array 6.0 and Illumina Human1m-duo) and in HapMap III project on an ordinary desktop computer. AVAILABILITY: (http://bioinfo.hku.hk/iggweb) (version 3.0).

Prevalence, Patterns, and Genetic Association Analysis of Modic Vertebral Endplate Changes.

STUDY DESIGN: A prospective genetic association study. PURPOSE: The etiology of Modic changes (MCs) is unclear. Recently, the role of genetic factors in the etiology of MCs has been evaluated. However, studies with a larger patient subset are lacking, and candidate genes involved in other disc degeneration phenotypes have not been evaluated. We studied the prevalence of MCs and genetic association of 41 candidate genes in a large Indian cohort. OVERVIEW OF LITERATURE: MCs are vertebral endplate signal changes predominantly observed in the lumbar spine. A significant association between MCs and lumbar disc degeneration and nonspecific low back pain has been described, with the etiopathogenesis implicating various mechanical, infective, and biochemical factors. METHODS: We studied 809 patients using 1.5-T magnetic resonance imaging to determine the prevalence, patterns, distribution, and type of lumbar MCs. Genetic association analysis of 71 single nucleotide polymorphisms (SNPs) of 41 candidate genes was performed based on the presence or absence of MCs. SNPs were genotyped using the Sequenome platform, and an association test was performed using PLINK software. RESULTS: The mean age of the study population (n=809) was 36.7±10.8 years. Based on the presence of MCs, the cohort was divided into 702 controls and 107 cases (prevalence, 13%). MCs were more commonly present in the lower (149/251, 59.4%) than in the upper (102/251, 40.6%) endplates. L4-5 endplates were the most commonly affected levels (30.7%). Type 2 MCs were the most commonly observed pattern (n=206, 82%). The rs2228570 SNP of VDR (p=0.02) and rs17099008 SNP of MMP20 (p=0.03) were significantly associated with MCs. CONCLUSIONS: Genetic polymorphisms of SNPs of VDR and MMP20 were significantly associated with MCs. Understanding the etiopathogenetic mechanisms of MCs is important for planning preventive and therapeutic strategies.

Genetic Polymorphisms in Estrogen Metabolic Pathway Associated with Risks of Alzheimer's Disease: Evidence from a Southern Chinese Population.

OBJECTIVES: To investigate whether genetic variations on the estrogen metabolic pathway would be associated with risk of Alzheimer's disease (AD). DESIGN: Cross-sectional study. SETTING: Individuals were recruited at the Memory Clinic, Queen Mary Hospital, Hong Kong. PARTICIPANTS: Chinese individuals with (n = 426) and without (n = 350) AD. MEASUREMENTS: All subjects underwent a standardized cognitive assessment and genotyping of four candidate genes on the estrogen metabolic pathway (estrogen receptor α gene (ESR1), estrogen receptor ß gene (ESR2), cytochrome P450 19A1 gene (CYP19A1), cytochrome P450 11A1 gene (CYP11A1)). RESULTS: Apart from consistent results showing an association between apolipoprotein (APO)E and AD, strong evidence of disease associations were found for polymorphisms in ESR2 and CYP11A1 based on the entire data set. For ESR2, significant protective effects were found for A alleles of rs4986938 (permuted P = .02) and rs867443 (permuted P = .02). For CYP11A1, significant risk effects were found for G alleles of rs11638442 (permuted P = .03) and rs11632698 (permuted P = .03). Stratifying subjects according to APOE ε4 status, their genetic effects continued to be significant in the APOE ε4-negative subgroup. Associations between CYP11A1 polymorphisms (rs2279357, rs2073475) and risk of AD were detected in women but not men. Further gene-level analysis confirmed the above association between ESR2 and CYP11A1, and pathway-level analysis highlighted the genetic effect of the estrogen metabolic pathway on disease susceptibility (permuted pathway-level P = .03). CONCLUSION: Consistent with previous biological findings for sex steroid hormones in the central nervous system, genetic alterations on the estrogen metabolic pathway were revealed in the Chinese population. Confirmation of these present findings in an independent population is warranted to elucidate disease pathogenesis and to explore the potential of hormone therapy in the treatment of AD.

Polymorphisms of CR1, CLU and PICALM confer susceptibility of Alzheimer's disease in a southern Chinese population.

In this case-controlled study, we tested susceptible genetic variants for Alzheimer's disease (AD) in CR1, CLU and PICALM from genome-wide association studies (GWAS) in a southern Chinese population. Eight hundred twelve participants consisting of 462 late-onset Alzheimer's disease (LOAD) patients and 350 nondemented control subjects were recruited. We found by multivariate logistic regression analysis, that single nucleotide polymorphisms (SNPs) in CR1 (rs6656401 adjusted allelic p = 0.035; adjusted genotypic p = 0.043) and CLU (rs2279590 adjusted allelic p = 0.035; adjusted genotypic p = 0.006; rs11136000 adjusted allelic p = 0.038; adjusted genotypic p = 0.009) were significantly different between LOAD patients and nondemented controls. For PICALM, LOAD association was found only in the APOE ε4 (-) subgroup (rs3851179 adjusted allelic p = 0.028; adjusted genotypic p = 0.013). Our findings showed evidence of CR1, CLU, and PICALM and LOAD susceptibility in an independent southern Chinese population, which provides additional evidence for LOAD association apart from prior genome-wide association studies in Caucasian populations.

Genetics of lumbar disk degeneration: technology, study designs, and risk factors.

Lumbar disk degeneration (LDD) is a common musculoskeletal condition. Genetic risk factors have been suggested to play a major role in its cause. This article reviews the main research strategies that have been used to study the genetics of LDD, and the genes that thus far have been identified to influence susceptibility to LDD. With the rapid progress in genomic technologies, further advances in the genetics of LDD are expected in the next few years.