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Chua kek heng

University of Malaya, Malaysia, Biomedical Science, Faculty Member

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Professor Dr. Chua Kek Heng is a professor of molecular biology at the Department of Biomedical Science, Faculty of Medicine, University of Malaya. Prof Chua is a molecular marker expert where his research areas include various disease polymorphism studies, mutation investigation studies, characterization of bacterial virulence factors and diagnostic kit development.
Address: Department of Biomedical Science, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, MALAYSIA.

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Papers by Chua kek heng

Association of JAK2 gene polymorphisms in Malaysian patients with Crohn’s disease

Crohn’s disease (CD) is one of the prominent subtypes of inflammatory bowel disease (IBD). It af... more Crohn’s disease (CD) is one of the prominent subtypes of inflammatory bowel disease (IBD). It affects any part of the gastrointestinal (GI) tract, especially colon and ileum. CD is on a rising trend in Asia, with prevalence of 26 cases per 100,000 population in Malaysia. To date, there is no cure available for CD. Although the exact cause of CD remains ambiguous, genetic factor has been shown to play a very important role in the development of CD. Janus kinase 2 (JAK2) is the key protein in JAK/STAT signalling pathway that regulates inflammatory response in mucosal barrier. Alteration of the JAK2 protein due to the changes in its gene could lead to unregulated inflammations that result in the onset of CD. Thus, we aim to study the association of JAK2 gene polymorphisms in Malaysian CD patients. A total of 99 CD patients and 297 matching controls were recruited from University Malaya Medical Centre. Venous blood was drawn and genomic DNA was extracted via a conventional phenol-c...

Detection of Helminth Eggs and Identification of Hookworm Species in Stray Cats, Dogs and Soil from Klang Valley, Malaysia

PloS one, 2015

The present study was conducted to determine the prevalence of helminth eggs excreted in the faec... more The present study was conducted to determine the prevalence of helminth eggs excreted in the faeces of stray cats, dogs and in soil samples. A total of 505 fresh samples of faeces (from 227 dogs and 152 cats) and soil were collected. The egg stage was detected via microscopy after the application of formalin-ether concentration technique. Genomic DNA was extracted from the samples containing hookworm eggs and used for further identification to the species level using real-time polymerase chain reaction coupled with high resolution melting analysis. Microscopic observation showed that the overall prevalence of helminth eggs among stray cats and dogs was 75.7% (95% CI = 71.2%-79.9%), in which 87.7% of dogs and 57.9% of cats were infected with at least one parasite genus. Five genera of heliminth eggs were detected in the faecal samples, including hookworms (46.4%), Toxocara (11.1%), Trichuris (8.4%), Spirometra (7.4%) and Ascaris (2.4%). The prevalence of helminth infections among str...

Bioinformatics in molecular immunology laboratories demonstrated: Modeling an anti-CMV scFv antibody

A scFv (single chain variable fragment) antibody clone from anti-CMV (anti-cucumber mosaic virus)... more A scFv (single chain variable fragment) antibody clone from anti-CMV (anti-cucumber mosaic virus) was successfully constructed from immunized mouse and the DNA sequence was submitted to GenBank (AY337618 and AY337619). The expression of a 32 kDa recombinant antibody in bacteria was verified using ELISA (enzyme-linked immunoassay) and western blot. However, elucidation of specific anti-CMV scFv function requires detailed and time consuming immuno-assays. Alternatively, useful functional information on anti-CMV scFV antibody can be obtained using available Bioinformatics tools and techniques without performing tedious assays. Here, we use the commonly used Bioinformatics tools and databases such as BLAST (basic local alignment search tool), GenBank, PDB (protein databank), KABAT numbering, SWISS-MODEL and Insight II to gain specific functional insights into anti-CMV scFv.

Multiple-Locus Variable-Number Tandem-Repeat Analysis for Clonal Identification of Vibrio parahaemolyticus Isolates by Using Capillary Electrophoresis

Applied and Environmental Microbiology, 2009

Epidemics of Vibrio parahaemolyticus in Chile have occurred since 1998. Direct genome restriction... more Epidemics of Vibrio parahaemolyticus in Chile have occurred since 1998. Direct genome restriction enzyme analysis (DGREA) using conventional gel electrophoresis permitted discrimination of different V. parahaemolyticus isolates obtained from these outbreaks and showed that this species consists of a highly diverse population. A multiple-locus variable-number tandem-repeat (VNTR) analysis (MLVA) approach was developed and applied to 22 clinical and 91 environmental V. parahaemolyticus isolates from Chile to understand their clonal structures. To this end, an advanced molecular technique was developed by applying multiplex PCR, fluorescent primers, and capillary electrophoresis, resulting in a high-resolution and high-throughput (HRHT) genotyping method. The genomic basis of this HRHT method was eight VNTR loci described previously by Kimura et al. (J. Microbiol. Methods 72:313-320, 2008) and two new loci which were identified by a detailed molecular study of 24 potential VNTR loci on...

Genetic diversity of circumsporozoite protein in Plasmodium knowlesi isolates from Malaysian Borneo and Peninsular Malaysia

Background Understanding the genetic diversity of candidate genes for malaria vaccines such as ci... more Background Understanding the genetic diversity of candidate genes for malaria vaccines such as circumsporozoite protein (csp) may enhance the development of vaccines for treating Plasmodium knowlesi. Hence, the aim of this study is to investigate the genetic diversity of non-repeat regions of csp in P. knowlesi from Malaysian Borneo and Peninsular Malaysia. Methods A total of 46 csp genes were subjected to polymerase chain reaction amplification. The genes were obtained from P. knowlesi isolates collected from different divisions of Sabah, Malaysian Borneo, and Peninsular Malaysia. The targeted gene fragments were cloned into a commercial vector and sequenced, and a phylogenetic tree was constructed while incorporating 168 csp sequences retrieved from the GenBank database. The genetic diversity and natural evolution of the csp sequences were analysed using MEGA6 and DnaSP ver. 5.10.01. A genealogical network of the csp haplotypes was generated using NETWORK ver. 4.6.1.3. Results The...

Amelioration of hyperglycemia-induced oxidative damage in ARPE-19 cells by myricetin derivatives isolated from Syzygium malaccense

Journal of Functional Foods, 2020

Myricetin derivatives (F2) isolated from leaf extract of Syzygium malaccense (Malay apple) which ... more Myricetin derivatives (F2) isolated from leaf extract of Syzygium malaccense (Malay apple) which contains myricitrin predominantly, could potentially serve as functional food ingredient based on previous findings. The present study aimed to investigate the protective effects of F2 against hyperglycemia-induced oxidative stress in ARPE-19 (retinal pigment epithelium) cells; a diabetic retinopathy (DR) model. F2 showed effective inhibition of advanced glycation end products (AGE) formation. The derivatives attenuated high glucose (30 mM)-induced stress condition in ARPE-19 cells by reducing intracellular reactive oxygen species (ROS). At transcriptional level, F2 activated Nrf2 pathway besides upregulating antioxidant enzymes and other protective factors. In addition, protective effect of F2 against formation of AGE correlated with its ability to downregulate gene expression of inflammatory factor, NFkB1 and receptor for AGE. The findings showed that F2 was effective in preventing oxidative damage-induced by high glucose in ARPE-19 and could be developed as an adjuvant to manage DR. Oxidative stress is well known to play a major role in the

Confirmation of five novel susceptibility loci for Systemic Lupus Erythematosus (SLE) and integrated network analysis of 82 SLE susceptibility loci

Human molecular genetics, Mar 20, 2017

We recently identified ten novel SLE susceptibility loci in Asians and uncovered several addition... more We recently identified ten novel SLE susceptibility loci in Asians and uncovered several additional suggestive loci requiring further validation. This study aimed to replicate five of these suggestive loci in a Han Chinese cohort from Hong Kong, followed by meta-analysis (11,656 cases and 23,968 controls) on previously reported Asian and European populations, and perform bioinformatic analyses on all 82 reported SLE loci to identify shared regulatory signatures. We performed a battery of analyses for these five loci, as well as joint analyses on all 82 SLE loci. All five loci passed genome-wide significance: MYNN (rs10936599, Pmeta=1.92x10(-13), OR = 0.88), ATG16L2 (rs11235604, Pmeta=8.87x10(-12), OR = 0.78), CCL22 (rs223881, Pmeta=5.87x10(-16), OR = 0.87), ANKS1A (rs2762340, Pmeta=4.93x10(-15), OR = 0.87) and RNASEH2C (rs1308020, Pmeta=2.96x10(-19), OR = 0.84) and co-located with annotated gene regulatory elements. The novel loci share genetic signatures with other reported SLE loc...

Significant Genotype Difference in the CYP2E1 PstI Polymorphism of Indigenous Groups in Sabah, Malaysia with Asian and Non-Asian Populations

Asian Pacific Journal of Cancer Prevention, 2014

CYP2E1 PstI polymorphism G-1259C (rs3813867) genotype distributions vary significantly among diff... more CYP2E1 PstI polymorphism G-1259C (rs3813867) genotype distributions vary significantly among different populations and are associated with both diseases, like cancer, and adverse drug effects. To date, there have been limited genotype distributions and allele frequencies of this polymorphism reported in the three major indigenous ethnic groups (KadazanDusun, Bajau, and Rungus) in Sabah, also known as North Borneo. The aim of this study was to investigate the genotype distributions and allele frequencies of the CYP2E1 PstI polymorphism G-1259C in these three major indigenous peoples in Sabah. A total of 640 healthy individuals from the three dominant indigenous groups were recruited for this study. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) at G-1259C polymorphic site of CYP2E1 gene was performed using the Pst I restriction enzyme. Fragments were analyzed using agarose gel electrophoresis and confirmed by direct sequencing. Overall, the allele frequencies were 90.3% for c1 allele and 9.7% for c2 allele. The genotype frequencies for c1/c1, c1/c2 and c2/c2 were observed as 80.9%, 18.8%, and 0.3%, respectively. A highly statistical significant difference (p<0.001) was observed in the genotype distributions between indigenous groups in Sabah with all Asian and non-Asian populations. However, among these three indigenous groups, there was no statistical significant difference (p>0.001) in their genotype distributions. The three major indigenous ethnic groups in Sabah show unique genotype distributions when compared with other populations. This finding indicates the importance of establishing the genotype distributions of CYP2E1 PstI polymorphism in the indigenous populations.

Variant Alleles in XRCC1 Arg194Trp and Arg399Gln Polymorphisms Increase Risk of Gastrointestinal Cancer in Sabah, North Borneo

Asian Pacific Journal of Cancer Prevention, 2016

Background: The XRCC1 protein facilitates various DNA repair pathways; single-nucleotide polymorp... more Background: The XRCC1 protein facilitates various DNA repair pathways; single-nucleotide polymorphisms (SNPs) in this gene are associated with a risk of gastrointestinal cancer (GIC) with inconsistent results, but no data have been previously reported for the Sabah, North Borneo, population. We accordingly investigated the XRCC1 Arg194Trp and Arg399Gln SNPs in terms of GIC risk in Sabah. Materials and Methods: We performed genotyping for both SNPs for 250 GIC patients and 572 healthy volunteers using a polymerase chain reactionrestriction fragment length polymorphism approach. We validated heterozygosity and homozygosity for both SNPs using direct sequencing. Results: The presence of a variant 194Trp allele in the Arg194Trp SNP was significantly associated with a higher risk of GIC, especially with gastric and colorectal cancers. We additionally found that the variant 399Gln allele in Arg399Gln SNP was associated with a greater risk of developing gastric cancer. Our combined analysis revealed that inheritance of variant alleles in both SNPs increased the GIC risk in Sabah population. Based on our etiological analysis, we found that subjects ≥50 years and males who carrying the variant 194Trp allele, and Bajau subjects carrying the 399Gln allele had a significantly increased risk of GIC. Conclusions: Our findings suggest that inheritance of variant alleles in XRCC1 Arg194Trp and Arg399Gln SNPs may act as biomarkers for the early detection of GIC, especially for gastric and colorectal cancers in the Sabah population.

Association of NOD1, CXCL16, STAT6 and TLR4 gene polymorphisms with Malaysian patients with Crohn's disease

PeerJ, 2016

Crohn's disease (CD) is a prominent type of inflammatory bowel disease (IBD) that can affect ... more Crohn's disease (CD) is a prominent type of inflammatory bowel disease (IBD) that can affect any part of the gastrointestinal tract. CD is known to have higher prevalence in the Western countries, but the number of cases has been increasing in the past decades in Asia, including Malaysia. Therefore, there is a need to investigate the underlining causes of CD that may shed light on its prevention and treatment. In this study, genetic polymorphisms in NOD1 (rs2075820), CXCL16 (rs2277680), STAT6 (rs324015) and TLR4 (rs4986791) genes were examined in a total of 335 individuals (85 CD patients and 250 healthy controls) with PCR-RFLP approach. There was no significant association observed between NOD1 rs2075820 and STAT6 rs324015 with the onset of CD in the studied cohort. However, the G allele of CXCL16 rs2277680 was found to have a weak association with CD patients (P = 0.0482; OR = 1.4310). The TLR4 rs4986791 was also significantly associated to CD. Both the homozygous C genotype (...

Attenuation of Inflammatory Mediators (TNF-α and Nitric Oxide) and Up-Regulation of IL-10 by Wild and Domesticated Basidiocarps of Amauroderma rugosum (Blume & T. Nees) Torrend in LPS-Stimulated RAW264.7 Cells

PLOS ONE, 2015

Amauroderma rugosum, commonly known as "Jia ˇzī " in China, is a wild mushroom traditionally used... more Amauroderma rugosum, commonly known as "Jia ˇzī " in China, is a wild mushroom traditionally used by the Chinese to reduce inflammation, to treat diuretic and upset stomach, and to prevent cancer. It is also used by the indigenous communities in Malaysia to prevent epileptic episodes and incessant crying by babies. The aim of this study was to compare the wild and domesticated basidiocarps of A. rugosum for antioxidant and in vitro anti-inflammatory effects in LPS-stimulated RAW264.7 cells. The wild basidiocarps of A. rugosum were collected from the Belum Forest, Perak, Malaysia and the domesticated basidiocarps of A. rugosum were cultivated in the mushroom house located in the University of Malaya, Kuala Lumpur, Malaysia. Both the wild and domesticated basidiocarps were subjected to ethanolic extraction and the extracts were tested for antioxidant and anti-inflammatory activities. In this study, the crude ethanolic extract of wild (WB) and domesticated (DB) basidiocarps of A. rugosum had comparable total phenolic content and DPPH scavenging activity. However, WB (EC 50 = 222.90 μg/mL) displayed a better ABTS cation radical scavenging activity than DB (EC 50 = 469.60 μg/mL). Both WB and DB were able to scavenge nitric oxide (NO) radical and suppress the NO production in LPS-stimulated RAW264.7 cells and this effect was mediated through the down-regulation of inducible nitric oxide synthase (iNOS) gene. In addition, both WB and DB caused down-regulation of the inflammatory gene TNF-α and the up-regulation of the anti-inflammatory gene IL-10. There was no inhibitory effect of WB and DB on nuclear translocation of NF-κB p65. In conclusion, the wild and domesticated basidiocarps of A. rugosum possessed antioxidant and in vitro anti-inflammatory properties.

Association between PDCD1 Gene Polymorphisms and Risk of Systemic Lupus Erythematosus in Three Main Ethnic Groups of the Malaysian Population

International Journal of Molecular Sciences, 2015

The programmed cell death 1 (PDCD1) gene encodes for the PD-1 (programmed death 1) molecule, whic... more The programmed cell death 1 (PDCD1) gene encodes for the PD-1 (programmed death 1) molecule, which negatively regulates self-reactive T-and B-cells in the maintenance of peripheral tolerance. A previous report had shown the development of lupus-like phenotypes in PD-1-deficient C57BL/6 mice, was suggestive to the role of PDCD1 in predisposing to systemic lupus erythematosus (SLE). Hence, we aimed to investigate the association between PDCD1 and SLE susceptibility in the Malaysian population. A TaqMan-based real-time PCR was employed to screen for PD1.1, PD1.3, PD1.5 and PD1.6 in both SLE and healthy control groups of 200 samples each. The observed frequency for PD1.5C/C genotype was significantly higher in Indian SLE patients and Malay controls (p < 0.01). On the other hand, the PD1.5C/T genotype might predispose the Malays to SLE, but confer a protective effect among the Indians (p < 0.01). The PD1.1, PD1.3 and PD1.6 were, however, not correlated to genetic predisposition of SLE in our Malaysian population.

DNA fingerprinting of human isolates of Burkholderia pseudomallei from different geographical regions of Malaysia

Tropical biomedicine, 2010

Melioidosis is an infectious disease caused by Burkholderia pseudomallei and endemic in Southeast... more Melioidosis is an infectious disease caused by Burkholderia pseudomallei and endemic in Southeast Asia. One hundred and forty six clinical isolates of B. pseudomallei from different states in Malaysia were obtained and molecular typing was carried out using pulsed-field gel electrophoresis (PFGE). Overall, nine clusters were successfully identified. Burkholderia pseudomallei isolates used in this study were found to be genetically diverse and there were differences in the clusters of isolates from peninsular and east Malaysia. BS9 cluster was the most common cluster and found in all the states while BS2 cluster only existed in a particular state. Based on the PFGE analysis, the distribution of different B. pseudomallei clinical isolates in Malaysia was mapped.

Correlation between gut microbiota composition and parasitic infection of pre-adolescence in Malaysia

Journal of Microbiology, Immunology and Infection, 2015

conducted by infecting both colonies with dengue type 1 virus. Mosquitoes were dissected on day 2... more conducted by infecting both colonies with dengue type 1 virus. Mosquitoes were dissected on day 2, 4, 8, 12 and 16 post infection to obtain salivary glands, midguts and ovaries. After extraction, presence of Wolbachia were determine using PCR and dengue virus load were determined using qPCR. Results: Wolbachia infected colonies had higher fecundity and egg viability compared to Wolbachia uninfected colony. Female lifespan for infected colony were slightly higher whereas male lifespan was significantly higher for Wolbachia uninfected colony. Virus titre load was the highest on day 12 for all three organs. Uninfected colony had higher viral amount on day 12 for salivary glands and midgut. The viral load in the ovaries were different at all intervals between Wolbachia infected and uninfected colonies. Conclusion: Wolbachia infected colonies had higher fecundity, longevity and egg viability compared to Wolbachia uninfected colonies but male lifespan were higher in Wolbachia uninfected colonies. Differences were noticeable in viral load pattern between Wolbachia infected and uninfected colonies for dengue type 1.

Whole-Genome Analysis of Aeromonas hydrophila Strain 187, Exhibiting Quorum-Sensing Activity

Genome announcements, 2014

Aeromonas hydrophila is a quorum-sensing (QS) bacterium that causes diarrhea in humans upon infec... more Aeromonas hydrophila is a quorum-sensing (QS) bacterium that causes diarrhea in humans upon infection. Here, we report the genome of pathogenic Aeromonas hydrophila strain 187, which possesses a QS gene responsible for signaling molecule N-acyl homoserine lactone (AHL) synthesis and has been found to be located at contig 36.

Insight into Gene Polymorphisms Involved in Toll-Like Receptor/Interferon Signalling Pathways for Systemic Lupus Erythematosus in South East Asia

Journal of Immunology Research, 2014

Polymorphisms in genes involved in toll-like receptor/interferon signalling pathways have been re... more Polymorphisms in genes involved in toll-like receptor/interferon signalling pathways have been reported previously to be associated with SLE in many populations. This study aimed to investigate the role of seven single nucleotide polymorphisms withinTNFAIP3,STAT4,andIRF5, which are involved in upstream and downstream pathways of type I interferon production, in SLE in the South East Asian populations. Genotyping of 360 Malaysian SLE patients and 430 normal healthy individuals revealed that minor alleles ofSTAT4rs7574865 and rs10168266 were associated with elevated risk of SLE in the Chinese and Malay patients, respectively (P=0.028, odds ratio(OR)=1.42;P=0.035,OR=1.80, respectively). Polymorphisms inTNFAIP3andIRF5did not show significant associations with SLE in any of the ethnicities. Combined analysis of the Malays, Chinese, and Indians for each SNP indicated thatSTAT4rs10168266 was significantly associated with the Malaysian SLE as a whole (P=0.014;OR=1.435). The meta-analysis of...

Plasmodium ovale infection in Malaysia: first imported case

Malaria journal, Jan 8, 2010

Plasmodium ovale infection is rarely reported in Malaysia. This is the first imported case of P. ... more Plasmodium ovale infection is rarely reported in Malaysia. This is the first imported case of P. ovale infection in Malaysia which was initially misdiagnosed as Plasmodium vivax. Peripheral blood sample was first examined by Giemsa-stained microscopy examination and further confirmed using a patented in-house multiplex PCR followed by sequencing. Initial results from peripheral blood smear examination diagnosed P. vivax infection. However further analysis using a patented in-house multiplex PCR followed by sequencing confirmed the presence of P. ovale. Given that Anopheles maculatus and Anopheles dirus, vectors of P. ovale are found in Malaysia, this finding has significant implication on Malaysia's public health sector. The current finding should serve as an alert to epidemiologists, clinicians and laboratory technicians in the possibility of finding P. ovale in Malaysia. P. ovale should be considered in the differential diagnosis of imported malaria cases in Malaysia due to th...

Increased detection of Plasmodium knowlesi in Sandakan division, Sabah as revealed by PlasmoNex™

Malaria Journal, 2013

Background Plasmodium knowlesi is a simian malaria parasite that is widespread in humans in Malay... more Background Plasmodium knowlesi is a simian malaria parasite that is widespread in humans in Malaysian Borneo. However, little is known about the incidence and distribution of this parasite in the Sandakan division, Malaysian Borneo. Therefore, the aim of the present epidemiological study was to investigate the incidence and distribution of P. knowlesi as well as other Plasmodium species in this division based on a most recent developed hexaplex PCR system (PlasmoNex™). Methods A total of 189 whole blood samples were collected from Telupid Health Clinic, Sabah, Malaysia, from 2008 to 2011. All patients who participated in the study were microscopically malaria positive before recruitment. Complete demographic details and haematological profiles were obtained from 85 patients (13 females and 72 males). Identification of Plasmodium species was conducted using PlasmoNex™ targeting the 18S ssu rRNA gene. Results A total of 178 samples were positive for Plasmodium species by using PlasmoN...

Transfusion-Dependent Thalassemia in Northern Sarawak: A Molecular Study to Identify Different Genotypes in the Multi-Ethnic Groups and the Importance of Genomic Sequencing in Unstudied Populations

Public Health Genomics, 2014

Background: Although thalassemia is a genetic hemoglobinopathy in Malaysia, there is limited data... more Background: Although thalassemia is a genetic hemoglobinopathy in Malaysia, there is limited data on thalassemia mutations in the indigenous groups. This study aims to identify the types of globin gene mutations in transfusion-dependent patients in Northern Sarawak. Methods: Blood was collected from 32 patients from the Malay, Chinese, Kedayan, Bisayah, Kadazandusun, Tagal, and Bugis populations. The α- and β-globin gene mutations were characterized using DNA amplification and genomic sequencing. Results: Ten β- and 2 previously reported α-globin defects were identified. The Filipino β-deletion represented the majority of the β-thalassemia alleles in the indigenous patients. Homozygosity for the deletion was observed in all Bisayah, Kadazandusun and Tagal patients. The β-globin gene mutations in the Chinese patients were similar to the Chinese in West Malaysia. Hb Adana (HBA2:c.179G>A) and the -α3.7/αα deletion were detected in 5 patients. A novel 24-bp deletion in the α2-globin ...

High Throughput Molecular Confirmation of β-Thalassemia Mutations Using Novel TaqMan Probes

Sensors, 2013

β-Thalassemia is a public health problem where 4.5% of Malaysians are β-thalassemia carriers. The... more β-Thalassemia is a public health problem where 4.5% of Malaysians are β-thalassemia carriers. The genetic disorder is caused by defects in the β-globin gene complex which lead to reduced or complete absence of β-globin chain synthesis. Five TaqMan genotyping assays were designed and developed to detect the common β-thalassemia mutations in Malaysian Malays. The assays were evaluated with 219 "blinded" DNA samples and the results showed 100% sensitivity and specificity. The in-house designed TaqMan genotyping assays were found to be cost-and time-effective for characterization of β-thalassemia mutations in the Malaysian population.