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Fulltext Rice millers' syndrome: a preliminary report

Lim HH, Domala Z, Joginder S, Lee SH, Lim CS, Abu Bakar CM

Br J Ind Med, 1984 Nov;41(4):445-9.
PMID: 6498108 DOI: 10.1136/oem.41.4.445

A study was carried out to determine the health effects of rice husk dust in Malaysian rice millers. The study population consisted of 122 male Malay workers from three rice mills, with 42 controls of similar age, sex, ethnic group, and agricultural work background. Interviews using standardised questionnaires, physical examination, total and differential white cell counts, chest radiographs, and lung function tests were performed on each of the millers and the controls. Environmental dust monitoring was also carried out in the three rice mills. Clinical, haematological, and radiological findings suggest that a distinct clinical syndrome seems to be associated with exposure to rice husk dust. The manifestations of this "rice millers' syndrome" include acute and chronic irritant effects affecting the eyes, skin, and upper respiratory tract; allergic responses such as nasal catarrh, tightness of chest, asthma, and eosinophilia; and radiological opacities in the chest, probably representing early silicosis or extrinsic allergic alveolitis.

Matched MeSH terms: Malaysia/ethnology
Serum HDL cholesterol and apolipoprotein AI, AII and B levels in Singapore newborns

Saha N, Wong HB

Biol. Neonate, 1987;52(2):93-6.
PMID: 3115319

The mortality from coronary artery disease (CAD) in Indians is more than three times that in the Chinese and Malays of Singapore. Serum total and HDL cholesterol as well as apolipoprotein (Apo) AI, AII and B levels were determined in a group of 349 newborns (cord blood) from both sexes in these three ethnic groups in order to examine if a trend is reflected at birth. Both serum LDL cholesterol and Apo B levels were low in the newborn, while HDL cholesterol and Apo AII levels were almost the same as in adults. Serum Apo AI levels were also low in newborns. No consistent difference as to ethnic group or sex was observed in any of the parameters investigated, except that the females had significantly higher levels of serum Apo AI in all the ethnic groups. Serum total and HDL cholesterol levels in Singapore newborns were comparable to those reported in Caucasians and Asians. The trends of incidence of CAD were not reflected in the lipid profiles studied at birth.

Matched MeSH terms: Malaysia/ethnology
Enamel defects in a fluoridated south-east Asian community

Chellappah NK, Vignehsa H, Lo GL

Aust Dent J, 1990 Dec;35(6):530-5.
PMID: 2090085

The prevalence and distribution patterns of enamel defects in maxillary incisors was assessed in 194 Singaporean children aged 11-15 years and belonging to three different ethnic groups. All were born and continuously resident in Singapore, which has a tropical climate. The water supply was fluoridated in 1957 at a level of 0.7 ppm. The mouth prevalence of defects was 71.5 per cent and the tooth prevalence was 55.9 per cent; 82 per cent of all affected teeth demonstrated white lesions of various forms. Although there was no sex difference in the prevalence and distribution pattern of defects, some racial differences were observed. The results were compared with data from other studies where the same classification of defects was used.

Matched MeSH terms: Malaysia/ethnology
Coagulation studies in Asian women using injectable progestogen for contraception

Tsakok FH, Koh S, Yuen R, Ratnam SS

Int J Gynaecol Obstet, 1980 9 1;18(2):105-8.
PMID: 6108245 DOI: 10.1002/j.1879-3479.1980.tb00256.x

Coagulation, fibrinolytic activity and platelet function were studied in 104 Asian women volunteers who received 150 mg of depot medroxyprogesterone acetate intramuscularly every three months for two years or more. The results were compared with those in matched controls. There was a paucity of change in coagulation factors. The fibrinogen levels were increased and prothrombin time was shortened. The fibrinolytic activity, as shown by the euglobulin clot lysis time, was significantly increased. This latter change contrasts with the many reports concerning Caucasian women and may reflect an increase in fibrinolytic potential in Asian women.

Matched MeSH terms: Malaysia/ethnology
Fulltext Corticosteroids causing severe growth suppression in juvenile rheumatoid arthritis

Lyn PCW

Med J Malaysia, 1984 Dec;39(4):300-5.
PMID: 6544938

Two children with Juvenile Rheumatoid Arthritis (JRA) and severe growth suppression from corticosteroid therapy are described. Prolonged 'tailing-off' of steroids occurred during outpatients follow-up and this may be related to the high turnover of doctors involved. Suggestions for improving such follow-ups and caution against the continuous use of steroids are made.
Study site: Queen Elizabeth Hospital, Kota Kinabalu, Sabah, Malaysia

Matched MeSH terms: Malaysia/ethnology
Fulltext Cardiovascular diseases in Chinese, Malays, and Indians in Singapore. II. Differences in risk factor levels

Hughes K, Yeo PP, Lun KC, Thai AC, Sothy SP, Wang KW, et al.

J Epidemiol Community Health, 1990 Mar;44(1):29-35.
PMID: 2348145 DOI: 10.1136/jech.44.1.29

STUDY OBJECTIVE: The aim of the study was to examine cardiovascular risk factors to see how these might explain differences in cardiovascular disease mortality among Chinese, Malays, and Indians in the Republic of Singapore.
DESIGN: The study was a population based cross sectional survey. Stratified systematic sampling of census districts, reticulated units, and houses was used. The proportions of Malay and Indian households were increased to improve statistical efficiency, since about 75% of the population is Chinese.
SETTING: Subjects were recruited from all parts of the Republic of Singapore.
SUBJECTS: 2143 subjects aged 18 to 69 years were recruited (representing 60.3% of persons approached). There were no differences in response rate between the sexes and ethnic groups.
MEASUREMENTS AND MAIN RESULTS: Data on cardiovascular risk factors were collected by questionnaire. Measurements were made of blood pressure, serum cholesterol, low and high density lipoprotein cholesterol, fasting triglycerides and plasma glucose. In males the age adjusted cigarette smoking rate was higher in Malays (53.3%) than in Chinese (37.4%) or Indians (44.5%). In both sexes, Malays had higher age adjusted mean systolic blood pressure: males 124.6 mm Hg v 121.2 mm Hg (Chinese) and 121.2 mm Hg (Indians); females 122.8 mm Hg v 117.3 mm Hg (Chinese) and 118.4 mm Hg (Indians). Serum cholesterol, low density lipoprotein cholesterol and triglyceride showed no ethnic differences. Mean high density lipoprotein cholesterol in males (age adjusted) was lower in Indians (0.69 mmol/litre) than in Chinese (0.87 mmol/litre) and Malays (0.82 mmol/litre); in females the mean value of 0.95 mmol/litre in Indians was lower than in Chinese (1.05 mmol/litre) and Malays (1.03 mmol/litre). Rank prevalence of diabetes for males was Indians (highest), Malays and then Chinese; for females it was Malays, Indians, Chinese.
CONCLUSIONS: The higher mortality from ischaemic heart disease found in Indians in Singapore cannot be explained by the major risk factors of cigarette smoking, blood pressure and serum cholesterol; lower high density lipoprotein cholesterol and higher rates of diabetes may be part of the explanation. The higher systolic blood pressures in Malays may explain their higher hypertensive disease mortality.

Matched MeSH terms: Malaysia/ethnology
Hepatitis B virus markers in prostitutes in Singapore

Goh CL, Kamarudin A, Chan SH, Rajan VS

Genitourin Med, 1985 Apr;61(2):127-9.
PMID: 3980022

The prevalence of hepatitis B virus markers in 121 men and 239 women prostitutes was studied. Of 33 (9.7%) with hepatitis B surface antigen (HBsAg), nine (27.3%) also had hepatitis Be antigen, which was more prevalent in men than women. Antibodies to HBsAg (anti-HBs) and to hepatitis B core antigen (anti-HBc) were found in about 71% of men and women prostitutes. Hepatitis B virus markers were more prevalent in men than in women prostitutes. Compared with other people, prostitutes had a significantly greater prevalence of hepatitis B virus markers. This study strongly suggested the importance of sexual transmission of infection with hepatitis B virus in a country where infection is endemic.

Matched MeSH terms: Malaysia/ethnology
A cross-sectional study of hepatitis B immune status in Asian children in Singapore

Quak SH, Singh R, Oon CJ, Wong HB

Ann Trop Paediatr, 1982 Jun;2(2):53-6.
PMID: 6185078

A study of race-related distribution of hepatitis B markers was conducted in 458 children admitted consecutively to Singapore General Hospital. The positive rates for hepatitis B surface antigen (HBsAg) in Chinese, Malays and Indians were 11.2, 8.0 and 12.2% respectively and the corresponding figures for anti-HBs were 30.2, 12.0 and 14.6%. In Chinese children HBsAg prevalence was shown to be sex-related, being higher in males than females. The percentages of Chinese children positive for anti-HBs and anti-HBc were also higher than those of the Indians. This study confirmed that Singapore children were exposed to hepatitis B infection from early life. All three races were equally susceptible to this infection.

Matched MeSH terms: Malaysia/ethnology
Intergroup perception as a compromise between in-group bias and fair-mindedness

Singh R, Sharmini, Choo I

J Soc Psychol, 2004 Aug;144(4):373-87.
PMID: 15279328

Previously, perceived competence of and attraction toward targets categorized by race showed in-group bias and no bias, respectively. Consequently, previous investigators regarded intergroup perception as a compromise between the norms of in-group bias and fair-mindedness. An alternative hypothesis for such findings is that attraction is not as relevant a dimension for intergroup discrimination as is competence. To test contrasting predictions of these hypotheses, the present authors asked participants from the majority and minority groups in Singapore (ns = 320) to evaluate either competence of or attraction toward one of the five targets. Consistent with the hypothesis that intergroup perception is a compromise, both dimensions yielded a uniform but weak in-group bias. The participants' equating of the in-group with one out-group further illustrated fair-mindedness. The authors discussed implications of the findings.

Matched MeSH terms: Malaysia/ethnology
Prevalence of Parkinson disease in Singapore: Chinese vs Malays vs Indians

Tan LC, Venketasubramanian N, Hong CY, Sahadevan S, Chin JJ, Krishnamoorthy ES, et al.

Neurology, 2004 Jun 08;62(11):1999-2004.
PMID: 15184604

OBJECTIVE: To investigate the prevalence of Parkinson disease (PD) in Singapore and compare the rates between Singaporean Chinese, Malays, and Indians.
METHODS: A three-phase community-based survey among a disproportionate random sample of 15,000 individuals (9,000 Chinese, 3,000 Malays, 3,000 Indians) aged 50 years and above who live in central Singapore was conducted. In phase 1, trained interviewers conducted a door-to-door survey using a validated 10-question questionnaire. In phase 2, medical specialists examined participants who screened positive to any of the questions. Participants suspected to have PD had their diagnosis confirmed in phase 3 by a movement disorders specialist.
RESULTS: The participation rate was 67% among 22,279 eligible individuals. Forty-six participants with PD were identified of which 16 were newly diagnosed cases. The prevalence rate of PD for those aged 50 and above in Singapore was 0.30% (95% CI: 0.22 to 0.41), age-adjusted to US 1970 census. The prevalence rates increased significantly with age. The age-adjusted prevalence rates among Chinese (0.33%, 95% CI: 0.22 to 0.48), Malays (0.29%, 95% CI: 0.13 to 0.67), and Indians (0.28%, 95% CI: 0.12 to 0.67) were the same (p = 1.0).
CONCLUSIONS: The prevalence of PD in Singapore was comparable to that of Western countries. Race-specific rates were also similar to previously reported rates and similar among the three races. Environmental factors may be more important than racially determined genetic factors in the development of PD.

Matched MeSH terms: Malaysia/ethnology
Fulltext Ethnic variations in female vulnerability after an acute coronary event

Mak KH, Kark JD, Chia KS, Sim LL, Foong BH, Ding ZP, et al.

Heart, 2004 Jun;90(6):621-6.
PMID: 15145860

OBJECTIVE: To determine the ethnic variation of short and long term female vulnerability after an acute coronary event in a population of Chinese, Indians, and Malays.
DESIGN: Population based registry.
PATIENTS: Residents of Singapore between the ages of 20-64 years with coronary events. Case identification and classification procedures were modified from the MONICA (monitoring trends and determinants in cardiovascular disease) project.
MAIN OUTCOME MEASURES: Adjusted 28 day case fatality and long term mortality.
RESULTS: From 1991 to 1999, there were 16 320 acute coronary events, including 3497 women. Age adjusted 28 day case fatality was greater in women (51.5% v 38.6%, p < 0.001), with a larger sex difference evident among younger Malay patients. This inequality between the sexes was observed in both the pre-hospitalisation and post-admission periods. Among hospitalised patients, women were older, were less likely to have suffered from a previous Q wave or anterior wall myocardial infarction, and had lower peak creatine kinase concentrations. Case fatality was higher among women, with adjusted hazard ratios of 1.64 (95% confidence interval (CI) 1.43 to 1.88) and 1.50 (95% CI 1.37 to 1.64) for 28 day and mean four year follow up periods. There were significant interactions of sex and age with ethnic group (p = 0.017). The adjusted hazards for mortality among Chinese, Indian, and Malay women versus men were 1.30, 1.71, and 1.96, respectively. The excess mortality among women diminished with age.
CONCLUSION: In this multiethnic population, both pre-hospitalisation and post-admission case fatality rates were substantially higher among women. The sex discrepancy in long term mortality was greatest among Malays and in the younger age groups.

Matched MeSH terms: Malaysia/ethnology
Factors influencing health-related quality of life of Asians with anxiety disorders in Singapore

Luo N, Fones CS, Thumboo J, Li SC

Qual Life Res, 2004 Mar;13(2):557-65.
PMID: 15085928 DOI: 10.1023/B:QURE.0000018484.89711.e2

As little is known about health-related quality of life (HRQoL) in Asians with anxiety disorders, we assessed HRQoL in Singaporeans with anxiety disorders and identified factors influencing their HRQoL. Outpatients with anxiety disorders (n = 119) attending a hospital psychiatric clinic completed the Short Form 36 Health Survey (SF-36), Beck Anxiety Inventory (BAI) and General Health Questionnaire (GHQ-12). SF-36 score reduction from population norms (quantified as the number of standard deviations below the mean) in these subjects was compared with existing data on Singaporeans with various medical conditions and Americans with panic disorder (PD). Factors influencing HRQoL were examined using stepwise multiple linear regression models. SF-36 score reduction in these subjects (0.3-1.4 SD) was greater than that in Singaporeans with systemic lupus erythematosus or thyroid cancer survivors for seven scales but similar to that in Americans with PD (0.5-1.7 SD). BAI and GHQ-12 scores, presence of PD/generalized anxiety disorder, presence of chronic medical conditions, being married or increasing age accounted for 19-61% of the variance in six selected SF-36 scales. In conclusion, it can be said that Singaporeans with anxiety disorders experience clinically important reductions in HRQoL; both clinical and socio-demographic factors influence HRQoL in such subjects.
Study site: Neuroscience Psychiatric Clinic, tertiary referral hospital, Singapore

Matched MeSH terms: Malaysia/ethnology
Higher failures of amelogenin sex test in an Indian population group

Chang YM, Burgoyne LA, Both K

J Forensic Sci, 2003 Nov;48(6):1309-13.
PMID: 14640276

The human sex test in forensic multiplexes is based on the amelogenin gene on both the X and Y chromosomes commonly used in sex genotyping. In this study of 338 male individuals in a Malaysian population comprising Malays, Chinese and Indians, using the AmpFlSTR Profiler Plus kit, the amelogenin test gave a significant proportion of null alleles in the Indian ethnic group (3.6% frequency) and 0.88% frequency in the Malay ethnic group due to a deletion of the gene on the Y chromosome. This sex test also failed in a forensic casework sample. Failure of the amelogenin test highlights the need for more reliable sex determination than is offered by the amelogenin locus in the Malay and Indian populations. The gender of the Indian-Malay amelogenin nulls was confirmed by the presence of three Y-STR alleles (DYS438, DYS390 and DYS439). For the Indian ethnic group, one of the Y-STR forms a stable haplotype with the amelogenin null. The amelogenin-deletion individuals also showed a null with a male-specific minisatellite MSY1, indicating that a very large deletion was involved that included the amelogenin and the MSY1 loci on the short arm of the Y chromosomes (Yp).

Matched MeSH terms: Malaysia/ethnology
Chlamydia pneumoniae IgG seropositivity and clinical history of ischemic heart disease in Singapore

Koh WP, Taylor MB, Chew SK, Phoon MC, Kang KL, Chow VT

J Microbiol Immunol Infect, 2003 Sep;36(3):169-74.
PMID: 14582560

There is still substantial uncertainty concerning the association between Chlamydia pneumoniae and ischemic heart disease. This may partly be explained by the adjustment for potential confounders in different population studies. This is the first study in Singapore to look at the association of C. pneumoniae seropositivity with ischemic heart disease in a multivariate analysis. A random sample of 714 persons aged between 35 and 69 years was selected from the participants of the Singapore National Health Survey conducted in 1998. Data on clinical measurements and conditions were collected using biochemical tests and interviewer-based questionnaires. Ischemic heart disease was defined by the Rose questionnaire and included history suggestive of angina and/or myocardial infarction. Immunoglobulin G antibodies for C. pneumoniae were detected using an indirect microimmunofluorescence test, and seropositivity was defined as IgG titers > or = 1:16. There were no statistically significant differences in the prevalence rates of seropositivity to C. pneumoniae among the three ethnic groups, that is, Chinese (80.4%), Malays (74.0%), and Asian Indians (73.2%). There was no association between seropositivity and ischemic heart disease after adjustment for age alone (OR 1.00, 95% CI 0.54-1.83) or for age, sex, and other risk factors of atherosclerosis (OR 0.99, 95% CI 0.53-1.84). C. pneumoniae Immunoglobulin G seropositivity was not associated with an increased risk of ischemic heart disease as defined by the Rose angina questionnaire in Singapore.

Matched MeSH terms: Malaysia/ethnology
Single-nucleotide polymorphisms of the interleukin-18 gene promoter region in rheumatoid arthritis patients: protective effect of AA genotype

Sivalingam SP, Yoon KH, Koh DR, Fong KY

Tissue Antigens, 2003 Dec;62(6):498-504.
PMID: 14617033 DOI: 10.1046/j.1399-0039.2003.00137.x

Rheumatoid arthritis (RA) is a chronic arthritic condition that can lead to deformities and disabilities. Although numerous studies reported the association of human leukocyte antigen (HLA)-DRB1*04 and RA, other genes, e.g. cytokines genes, may contribute towards disease susceptibility. Interleukin-18 (IL-18) is a proinflammatory cytokine postulated to play a role in the acute and chronic inflammatory phases of RA. The IL-18 protein expression seems to be regulated by two single-nucleotide polymorphisms (SNPs) located at positions -607 and -137 in the promoter region of the gene. It is postulated that specific alleles may be associated with susceptibility to the development of RA. In the present study, we described the IL-18 gene promoter region genotypes and combined genotypes (-607/-137) in 106 RA patients and 273 unrelated healthy controls to evaluate the contributions of these alleles to RA predisposition in Chinese, Malays, and Indians. The genotyping were performed using sequence-specific polymerase chain reactions. Rheumatoid factors were assayed by enzyme-linked immunosorbent assay. Biodata were obtained through chart review. The controls had significantly higher frequency of AA genotype at position -607 when compared to RA patients. No significant differences were observed in the distribution of either allelic or genotypic frequencies at position -137. There was no association between the genotypes and the presence of rheumatoid factors. This study did not find evidence of a genetic susceptibility factor but demonstrated the novel finding that the AA genotype at position -607 is associated with a protective effect against development of RA in Chinese individuals. This protection may be mediated through inhibition of cyclic (Adenosine 3', 5'-cyclic monophosphate) AMP-responsive element (CRE)-binding protein by the disruption of the CRE consensus sequence.

Matched MeSH terms: Malaysia/ethnology
University students and mental health. Canada, Britain and Singapore

Gold JH

Int J Soc Psychiatry, 1979;25(2):84-91.
PMID: 511452

There are many crucial determinants of the individual outcome and benefit of a university education including the stressful interplay of cultural and socioeconomic factors which are of growing importance in the inflationary 1970's. An epidemiological study of university students from 1969-1972 in Canada, 1973-1974 in Britain, and 1975 in Singapore, attempted to identify stresses leading to mental ill-health in these students. Singapore was chosen as an example of a culture bridging the developed Northern and developing Southern nations of the world. Cultural differences affecting the results of the study are discussed as is the role of social change.

Matched MeSH terms: Malaysia/ethnology
BRCA1 c.2845insA is a recurring mutation with a founder effect in Singapore Malay women with early onset breast/ovarian cancer

Sng JH, Ali AB, Lee SC, Zahar D, Wong JE, Blake V, et al.

J Med Genet, 2003 Oct;40(10):e117.
PMID: 14569140
Matched MeSH terms: Malaysia/ethnology
Ancestry-informative marker (AIM) SNP panel for the Malay population

Yahya P, Sulong S, Harun A, Wangkumhang P, Wilantho A, Ngamphiw C, et al.

Int J Legal Med, 2020 Jan;134(1):123-134.
PMID: 31760471 DOI: 10.1007/s00414-019-02184-0

Ancestry-informative markers (AIMs) can be used to infer the ancestry of an individual to minimize the inaccuracy of self-reported ethnicity in biomedical research. In this study, we describe three methods for selecting AIM SNPs for the Malay population (Malay AIM panel) using different approaches based on pairwise FST, informativeness for assignment (In), and PCA-correlated SNPs (PCAIMs). These Malay AIM panels were extracted from genotype data stored in SNP arrays hosted by the Malaysian node of the Human Variome Project (MyHVP) and the Singapore Genome Variation Project (SGVP). In particular, genotype data from a total of 165 Malay individuals were analyzed, comprising data on 117 individual genotypes from the Affymetrix SNP-6 SNP array platform and data on 48 individual genotypes from the OMNI 2.5 Illumina SNP array platform. The HapMap phase 3 database (1397 individuals from 11 populations) was used as a reference for comparison with the Malay genotype data. The accuracy of each resulting Malay AIM panel was evaluated using a machine learning "ancestry-predictive model" constructed by using WEKA, a comprehensive machine learning platform written in Java. A total of 1250 SNPs were finally selected, which successfully identified Malay individuals from other world populations with an accuracy of 90%, but the accuracy decreased to 80% using 157 SNPs according to the pairwise FST method, while a panel of 200 SNPs selected using In and PCAIMs could be used to identify Malay individuals with an accuracy of approximately 80%.

Matched MeSH terms: Malaysia/ethnology
Fulltext Calculation of free and bioavailable vitamin D and its association with bone mineral density in Malaysian women

Thambiah SC, Wong TH, Das Gupta E, Radhakrishnan AK, Gun SC, Chembalingam G, et al.

Malays J Pathol, 2018 Dec;40(3):287-294.
PMID: 30580359

INTRODUCTION: Low 25-hydroxyvitamin D [25(OH)D] levels have not been consistently associated with bone mineral density (BMD). It has been suggested that calculation of the free/bioavailable 25(OH)D may correlate better with BMD. We examined this hypothesis in a cohort of Malaysian women.

MATERIALS AND METHODS: A cross-sectional study of 77 patients with rheumatoid arthritis (RA) and 29 controls was performed. Serum 25(OH)D was measured using the Roche Cobas E170 immunoassay. Serum vitamin D binding protein (VDBP) was measured using a monoclonal enzyme-linked immunosorbent assay (ELISA). Free/bioavailable 25(OH)D were calculated using both the modified Vermuelen and Bikle formulae.

RESULTS: Since there were no significant differences between RA patients and controls for VDBP and 25(OH)D, the dataset was analysed as a whole. Calculated free 25(OH)D by Vermeulen was strongly correlated with Bikle (r = 1.00, p < 0.001). A significant positive correlation was noted between measured total 25(OH)D with free/bioavailable 25(OH)D (r = 0.607, r = 0.637, respectively, p < 0.001). Median free/bioavailable 25(OH)D values were significantly higher in Chinese compared with Malays and Indians, consistent with their median total 25(OH)D. Similar to total 25(OH)D, the free/bioavailable 25(OH)D did not correlate with BMD.

CONCLUSION: In this first study of a multiethnic female Malaysian population, free/bioavailable 25(OH)D were found to reflect total 25(OH)D, and was not superior to total 25(OH)D in its correlation with BMD. Should they need to be calculated, the Bikle formula is easier to use but only calculates free 25(OH)D. The Vermuelen formula calculates both free/bioavailable 25(OH)D but is more complex to use.

Matched MeSH terms: Malaysia/ethnology
The population genomic landscape of human genetic structure, admixture history and local adaptation in Peninsular Malaysia

Deng L, Hoh BP, Lu D, Fu R, Phipps ME, Li S, et al.

Hum Genet, 2014 Sep;133(9):1169-85.
PMID: 24916469 DOI: 10.1007/s00439-014-1459-8

Peninsular Malaysia is a strategic region which might have played an important role in the initial peopling and subsequent human migrations in Asia. However, the genetic diversity and history of human populations--especially indigenous populations--inhabiting this area remain poorly understood. Here, we conducted a genome-wide study using over 900,000 single nucleotide polymorphisms (SNPs) in four major Malaysian ethnic groups (MEGs; Malay, Proto-Malay, Senoi and Negrito), and made comparisons of 17 world-wide populations. Our data revealed that Peninsular Malaysia has greater genetic diversity corresponding to its role as a contact zone of both early and recent human migrations in Asia. However, each single Orang Asli (indigenous) group was less diverse with a smaller effective population size (N(e)) than a European or an East Asian population, indicating a substantial isolation of some duration for these groups. All four MEGs were genetically more similar to Asian populations than to other continental groups, and the divergence time between MEGs and East Asian populations (12,000--6,000 years ago) was also much shorter than that between East Asians and Europeans. Thus, Malaysian Orang Asli groups, despite their significantly different features, may share a common origin with the other Asian groups. Nevertheless, we identified traces of recent gene flow from non-Asians to MEGs. Finally, natural selection signatures were detected in a batch of genes associated with immune response, human height, skin pigmentation, hair and facial morphology and blood pressure in MEGs. Notable examples include SYN3 which is associated with human height in all Orang Asli groups, a height-related gene (PNPT1) and two blood pressure-related genes (CDH13 and PAX5) in Negritos. We conclude that a long isolation period, subsequent gene flow and local adaptations have jointly shaped the genetic architectures of MEGs, and this study provides insight into the peopling and human migration history in Southeast Asia.

Matched MeSH terms: Malaysia/ethnology

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