Eric Yap

Does education explain ethnic differences in myopia prevalence? A population-based study of young adult males in Singapore

Purpose. To study interethnic variation in myopia prevalence and severity in young adult males in Singapore and to determine whether these variations are related to differences in education level. Methods. A population-based survey of refractive errors in a cohort of 15,095 military conscripts between July 1996 and June 1997 using noncycloplegic autorefraction and a standard questionnaire. Prevalence rates of myopia (<−0.5D) and severe myopia (<−6.0 D) were determined for Chinese, Malay, and Indian men; prevalence rate ratios were compared after adjusting for education level. Results. Singapore has one of the highest prevalences of myopia (79.3%) and severe myopia (13.1%), with Chinese having higher rates (82.2%, 95% confidence interval 81.5, 82.9) compared with Indians (68.7%, 95% confidence interval 65.1, 67.1) and Malays (65.0%, 95% confidence interval 62.9, 67.1). Education was strongly associated with prevalence and severity of myopia. However, significant interethnic variation persisted after adjusting for education. Conclusions. There is a high prevalence of myopia in Singapore. Although prevalence and severity of myopia were strongly associated with education, interethnic variation observed was not fully explained by differences in education level.

Academic achievement, close up work parameters, and myopia in Singapore military conscripts

AIM To determine the relation of refractive error to environmental factors, including close up work, in Singapore military conscripts. METHODS A cross sectional study was conducted on 429 Singapore military conscripts. Non-cycloplegic refraction and A-scan biometry were performed in both eyes. A detailed questionnaire was administered by in-person interview to obtain information about current and past near work activity, extra tuition lessons, educational experiences, and family demographics. RESULTS Myopia associated with the conscript having been educated in the (gifted, special, or express) educational streams (adjusted odds ratio (OR) = 3.8, 95% confidence interval CI 2.0–7.3), and having completed pre-university education (OR=4.1, 95% CI 1.9–8.8). The reported close up work activity at age 7 years did correlate with age of onset of myopia (p<0.001). In parallel, supplemental tuition lessons in primary school has (OR=2.6, 95% CI 1.4–4.9) associated with conscript myopia. Parental myopia was positively associated with myopia (p<0.001), but this relation disappeared when adjusted for environmental factors. Current (p=0.83) and past close up work activity at age 7 years (p=0.13) did not correlate with myopia. CONCLUSION Educational level and educational stream positively related to myopia. A relation was observed with reported close up work activity in early childhood and with tuition classes during elementary school, but not with current close up work activity. These results underscore the strong influence of environment in myopia pathogenesis but a role for close up work activity remains indeterminate.

Deep whole-genome sequencing of 100 southeast Asian Malays.

Whole-genome sequencing across multiple samples in a population provides an unprecedented opportunity for comprehensively characterizing the polymorphic variants in the population. Although the 1000 Genomes Project (1KGP) has offered brief insights into the value of population-level sequencing, the low coverage has compromised the ability to confidently detect rare and low-frequency variants. In addition, the composition of populations in the 1KGP is not complete, despite the fact that the study design has been extended to more than 2,500 samples from more than 20 population groups. The Malays are one of the Austronesian groups predominantly present in Southeast Asia and Oceania, and the Singapore Sequencing Malay Project (SSMP) aims to perform deep whole-genome sequencing of 100 healthy Malays. By sequencing at a minimum of 30× coverage, we have illustrated the higher sensitivity at detecting low-frequency and rare variants and the ability to investigate the presence of hotspots of functional mutations. Compared to the low-pass sequencing in the 1KGP, the deeper coverage allows more functional variants to be identified for each person. A comparison of the fidelity of genotype imputation of Malays indicated that a population-specific reference panel, such as the SSMP, outperforms a cosmopolitan panel with larger number of individuals for common SNPs. For lower-frequency (<5%) markers, a larger number of individuals might have to be whole-genome sequenced so that the accuracy currently afforded by the 1KGP can be achieved. The SSMP data are expected to be the benchmark for evaluating the value of deep population-level sequencing versus low-pass sequencing, especially in populations that are poorly represented in population-genetics studies.

Real-Time Fluorescence-Based PCR for Detection of Malaria Parasites

ABSTRACT A fluorescence-based real-time 5′ nuclease PCR capable of detecting all four human malaria parasites was developed to screen large numbers of samples during an outbreak to prevent further transmission of malaria. The effectiveness of antimalarial therapy for malaria patients can be monitored by determining the reduction of parasitemia by this method.

Genome-wide association studies reveal genetic variants in CTNND2 for high myopia in Singapore Chinese

OBJECTIVE To determine susceptibility genes for high myopia in Singaporean Chinese. DESIGN A meta-analysis of 2 genome-wide association (GWA) datasets in Chinese and a follow-up replication cohort in Japanese. PARTICIPANTS AND CONTROLS Two independent datasets of Singaporean Chinese individuals aged 10 to 12 years (Singapore Cohort Study of the Risk factors for Myopia [SCORM]: cases = 65, controls = 238) and more than 21 years (Singapore Prospective Study Program [SP2]: cases = 222, controls = 435) for GWA studies, and a Japanese dataset aged more than 20 years (cases = 959, controls = 2128) for replication. METHODS Genomic DNA samples from SCORM and SP2 were genotyped using various Illumina Beadarray platforms (>HumanHap 500). Single-locus association tests were conducted for each dataset with meta-analysis using pooled z-scores. The top-ranked genetic markers were examined for replication in the Japanese dataset. Fisher P was calculated for the combined analysis of all 3 cohorts. MAIN OUTCOME MEASURES High myopia, defined by spherical equivalent (SE) ≤ -6.00 diopters (D); controls defined by SE between -0.50 and +1.00 D. RESULTS Two SNPs (rs12716080 and rs6885224) in the gene CTNND2 on chromosome 5p15 ranked top in the meta-analysis of our Chinese datasets (meta P = 1.14 × 10(-5) and meta P = 1.51 × 10(-5), respectively) with strong supporting evidence in each individual dataset analysis (max P = 1.85 × 10(-4) in SCORM: max P = 8.8 × 10(-3) in SP2). Evidence of replication was observed in the Japanese dataset for rs6885224 (P = 0.035, meta P of 3 datasets: 7.84 × 10(-6)). CONCLUSIONS This study identified a strong association of CTNND2 for high myopia in Asian datasets. The CTNND2 gene maps to a known high myopia linkage region on chromosome 5p15.

Effect of Blast Exposure on the Brain Structure and Cognition in Macaca fascicularis

Blast injury to the brain is one of the major causes of death and can also significantly affect cognition and physical and psychological skills in survivors of blast. The complex mechanisms via which blast injury causes impairment of cognition and other symptoms are poorly understood. In this study, we investigated the effects of varying degrees of primary blast overpressure (BOP; 80 and 200 kPa) on the pathophysiological and magnetic resonance imaging (MRI) changes and neurocognitive performance as assessed by the monkey Cambridge Neuropsychological Test Automated Battery (mCANTAB) in non-human primates (NHP). The study aimed to examine the effects of neurobehavioral and histopathological changes in NHP. MRI and histopathology revealed ultrastructural changes in the brain, notably in the Purkinje neurons in the cerebellum and pyramidal neurons in the hippocampus, which were most vulnerable to the blast. The results correlated well with the behavioral changes and changes in motor coordination and working memory of the affected monkeys. In addition, there was white matter damage affecting myelinated axons, astrocytic hypertrophy, and increased aquaporin-4 (AQP-4) expression in astrocytes, suggesting cerebral edema. Increased apoptosis appeared to involve astrocytes and oligodendrocytes in the animals following blast exposure. The small sample size could have contributed to the non-significant outcome in cognitive performance post-blast and limited quantitative analyses. Nevertheless, the study has provided initial descriptive changes for establishing a primary BOP threshold for brain injury to serve as a useful platform for future investigations that aim to estimate brain injury potential and set safe limits of exposure.

Development of a Next-Generation Sequencing Method for BRCA Mutation Screening : A Comparison between a High-Throughput and a Benchtop Platform

In a clinical setting, next-generation sequencing (NGS) approaches for the enrichment and resequencing of DNA targets may have limitations in throughput, cost, or accuracy. We evaluated an NGS workflow for targeted DNA sequencing for mutation detection. Targeted sequence data of the BRCA1 and BRCA2 genes, generated using a PCR-based, multiplexed NGS approach using the SOLiD 4 (n = 24) and Ion Torrent PGM (n = 20) next-generation sequencers, were evaluated against sequence data obtained by Sanger sequencing. The overall sensitivity for SOLiD and PGM were 97.8% (95% CI = 94.7 to 100.0) and 98.9% (95% CI = 96.8 to 100.0) respectively. The specificity for the SOLiD platform was high, at 100.0% (95% CI = 99.3 to 100.0). PGM correctly identified all 3 indels, but 68 false-positive indels were also called. Equimolar normalization of amplicons was not necessary for successful NGS. Both platforms are highly amenable to scale-up, potentially reducing the reagent cost for BRCA testing to <US

Genome-wide association study identifies ZFHX1B as a susceptibility locus for severe myopia

200. Only 325 ng of DNA per patient is required, with similar coverage and accuracy obtained using DNA derived from peripheral blood or buccal wash samples. The strategy described is accurate and easy to incorporate into conventional workflow, and shows potential for mutation screening of clinically important gene targets in genetic disorders.

Association between an intronic apolipoprotein E polymorphism and bone mineral density in Singaporean Chinese females.

Severe myopia (defined as spherical equivalent < -6.0 D) is a predominant problem in Asian countries, resulting in substantial morbidity. We performed a meta-analysis of four genome-wide association studies (GWAS), all of East Asian descent totaling 1603 cases and 3427 controls. Two single nucleotide polymorphisms (SNPs) (rs13382811 from ZFHX1B [encoding for ZEB2] and rs6469937 from SNTB1) showed highly suggestive evidence of association with disease (P < 1 × 10(-7)) and were brought forward for replication analysis in a further 1241 severe myopia cases and 3559 controls from a further three independent sample collections. Significant evidence of replication was observed, and both SNP markers surpassed the formal threshold for genome-wide significance upon meta-analysis of both discovery and replication stages (P = 5.79 × 10(-10), per-allele odds ratio (OR) = 1.26 for rs13382811 and P = 2.01 × 10(-9), per-allele OR = 0.79 for rs6469937). The observation at SNTB1 is confirmatory of a very recent GWAS on severe myopia. Both genes were expressed in the human retina, sclera, as well as the retinal pigmented epithelium. In an experimental mouse model for myopia, we observed significant alterations to gene and protein expression in the retina and sclera of the unilateral induced myopic eyes for Zfhx1b and Sntb1. These new data advance our understanding of the molecular pathogenesis of severe myopia.

Association of intronic single-nucleotide polymorphisms in the EMILIN1 gene with essential hypertension in a Chinese population

INTRODUCTION Apolipoprotein E (ApoE) is implicated in the pathogenesis of osteoporosis. OBJECTIVE To investigate possible association of the non-classical APOE gene +113C/G (rs440446) intron 1 enhancer polymorphism with bone mineral density (BMD) in a homogeneous Chinese population in Singapore. METHODS A total of 655 volunteers, males and females, aged between 31 and 72 years, from the public participated. BMD was measured using dual-energy X-ray absorptiometry and APOE +113C/G (rs440446) genotypes were determined by Sequenom MassARRAY system. To adjust for potential confounders, anthropometric, demographic, and lifestyle determinants were obtained, and serum lipids and E(2) were measured. RESULTS The +113C/G (rs440446) polymorphism within the APOE gene was associated with BMD in Chinese Singaporean females only. Females with the heterozygous CG genotype were significantly associated with reduced total, lumbar spine, and femoral neck of hip BMD, after multilevel adjustment of confounders. The association was stronger in the spine than in the hip. When females were stratified according to WHO classification for osteoporosis, those with CG and GG genotypes had increased risk (OR 3.50 and 2.22, respectively) of developing osteopenia/osteoporosis in the lumbar spine. Serum lipids did not explain the influence of APOE +113 C/G (rs440446) on BMD. CONCLUSION This study demonstrated an association between APOE +113C/G (rs440446) polymorphism with measures of BMD in Singaporean Chinese females.