Displaying publications 1 - 20 of 121 in total

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  1. Zainuddin N, Jaafar H, Isa MN, Abdullah JM
    PMID: 16124450
    Frequent loss of heterozygosity (LOH) and mutations of the tumor suppressor gene PTEN (phosphatase and tensin homologue deleted from chromosome 10) have been found in sporadic gliomas. The most documented regions of allelic losses include 9p21, 10q23-25 and 17p1 3 whereas PTEN aberrations are preferentially found in glioblastoma multiformes. This research aimed to detect the incidence of allelic losses on chromosomes 10q, 9p, 17p and 13q and mutations on exons 5, 6 and 8 of PTEN in malignant gliomas. Malignant glioma specimens obtained were classified histopathologically according to the WHO criteria. Each tumor was then subjected to polymerase chain reaction (PCR)-LOH analysis using microsatellite markers and single-stranded conformational polymorphism (SSCP) analysis. Twelve of 23 (52%) malignant glioma cases showed allelic losses whereas 7 of 23 (30%) samples showed aberrant band patterns and mutations of PTEN. Four of these cases showed LOH in 10q23 and mutations of PTEN. The data on LOH indicated the involvement of different genes in the genesis of glioma whereas mutations of PTEN indicated the role of PTEN tumor suppressor gene in the progression of glioma in Malay population.
    Matched MeSH terms: Mutation/genetics
  2. Zainuddin N, Jaafart H, Isa MN, Abdullah JM
    Neurol Res, 2004 Jan;26(1):88-92.
    PMID: 14977064
    Recent advances in neuro-oncology have revealed different pathways of molecular oncogenesis in malignant gliomas including loss of heterozygosity on chromosomal regions harboring tumor suppressor genes. In the present study, we performed polymerase chain reaction-loss of heterozygosity (PCR-LOH) analysis using microsatellite markers to identify loss of heterozygosity on chromosomes 10q, 9p, 17p and 13q in the Malays with malignant gliomas. Of 12 cases with allelic losses, seven (58.3%) cases showed LOH on chromosome 10q, three (25.0%) cases showed LOH on chromosome 9p, four (33.3%) cases showed LOH on chromosome 17p and two (16.7%) cases showed LOH on chromosome 13q. The cases include five (41.7%) cases of glioblastoma multiforme, three (25.0%) cases of anaplastic astrocytoma, three (25.0%) cases of anaplastic oligodendroglioma and one (8.3%) case of anaplastic ependymoma. Four cases showed loss of heterozygosity on more than one locus. Our findings showed that loss of heterozygosity on specific chromosomal regions contributes to the molecular pathway of glioma progression in Malay population. In addition, these data provide useful evidence of molecular genetic alterations of malignant glioma in South East Asian patients, particularly in the East Coast of Malaysia.
    Matched MeSH terms: Mutation/genetics*
  3. Zahary MN, Kaur G, Hassan MR, Sidek AS, Singh H, Yeh LY, et al.
    Int J Colorectal Dis, 2014 Feb;29(2):261-2.
    PMID: 24072394 DOI: 10.1007/s00384-013-1770-1
    Matched MeSH terms: Germ-Line Mutation/genetics*
  4. Yusoff AA, Abdullah J, Abdullah MR, Mohd Ariff AR, Isa MN
    Acta Neurochir (Wien), 2004 Jun;146(6):595-601.
    PMID: 15168228
    Alteration of the tumor suppressor gene p53 is considered to be a critical step in the development of human cancer. Changes in this gene have been detected in a wide range of human tumours, including gliomas. In glioma, the presence of p53 gene alterations has been associated with worse prognosis.
    Matched MeSH terms: Frameshift Mutation/genetics; Point Mutation/genetics
  5. Yunus NM, Johan MF, Ali Nagi Al-Jamal H, Husin A, Hussein AR, Hassan R
    Asian Pac J Cancer Prev, 2015;16(12):4869-72.
    PMID: 26163606
    BACKGROUND: Mutations of the FMS-like tyrosine kinase-3 (FLT3) receptor gene may promote proliferation via activation of multiple signaling pathways. FLT3-internal tandem duplication (FLT3-ITD) is the most common gene alteration found in patients diagnosed with acute myeloid leukaemia (AML) and has been associated with poor prognosis.

    MATERIALS AND METHODS: We performed mutational analysis of exons 14-15 and 20 of the FLT3 gene in 54 AML patients using PCR-CSGE (conformational sensitive gel electrophoresis) followed by sequencing analysis to characterise FLT3 mutations in adult patients diagnosed with AML at Hospital USM, Kelantan, Northeast Peninsular Malaysia.

    RESULTS: FLT3 exon 14-15 mutations were identified in 7 of 54 patients (13%) whereas no mutation was found in FLT3 exon 20. Six ITDs and one non-ITD mutation were found in exon 14 of the juxtamembrane (JM) domain of FLT3. FLT3-ITD mutations were associated with a significantly higher blast percentage (p-value=0.008) and white blood cell count (p-value=0.023) but there was no significant difference in median overall survival time for FLT3-ITD+/FLT3-ITD- within 2 years (p-value=0.374).

    CONCLUSIONS: The incidence of FLT3-ITD in AML patients in this particular region of Malaysia is low compared to the Western world and has a significant association with WBC and blast percentage.

    Matched MeSH terms: Mutation/genetics*
  6. Yenchitsomanus PT, Sawasdee N, Paemanee A, Keskanokwong T, Vasuvattakul S, Bejrachandra S, et al.
    J Hum Genet, 2003;48(9):451-456.
    PMID: 12938018 DOI: 10.1007/s10038-003-0059-6
    We have previously demonstrated that compound heterozygous (SAO/G701D) and homozygous (G701D/G701D) mutations of the anion exchanger 1 (AE1) gene, encoding erythroid and kidney AE1 proteins, cause autosomal recessive distal renal tubular acidosis (AR dRTA) in Thai patients. It is thus of interest to examine the prevalence of these mutations in the Thai population. The SAO and G701D mutations were examined in 844 individuals from north, northeast, central, and south Thailand. Other reported mutations including R602H, DeltaV850, and A858D were also examined in some groups of subjects. The SAO mutation was common in the southern Thai population; its heterozygote frequency was 7/206 and estimated allele frequency 1.70%. However, this mutation was not observed in populations of three other regions of Thailand. In contrast, the G701D mutation was not found in the southern population but was observed in the northern, northeastern, and central populations, with heterozygote frequencies of 1/216, 3/205, and 1/217, and estimated allele frequencies of 0.23%, 0.73%, and 0.23%, respectively. The higher allele frequency of the G701D mutation in the northeastern Thai population corresponds to our previous finding that all Thai patients with AR dRTA attributable to homozygous G701D mutation originate from this population. This suggests that the G701D allele that is observed in this region might arise in northeastern Thailand. The presence of patients with compound heterozygous SAO/G701D in southern Thailand and Malaysia and their apparently absence in northeastern Thailand indicate that the G701D allele may have migrated to the southern peninsular region where SAO is common, resulting in pathogenic allelic interaction.
    Matched MeSH terms: Mutation/genetics*
  7. Yatabe Y, Kerr KM, Utomo A, Rajadurai P, Tran VK, Du X, et al.
    J Thorac Oncol, 2015 Mar;10(3):438-45.
    PMID: 25376513 DOI: 10.1097/JTO.0000000000000422
    The efficacy of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors in EGFR mutation-positive non-small-cell lung cancer (NSCLC) patients necessitates accurate, timely testing. Although EGFR mutation testing has been adopted by many laboratories in Asia, data are lacking on the proportion of NSCLC patients tested in each country, and the most commonly used testing methods.
    Matched MeSH terms: Mutation/genetics*
  8. Yap PS, Cheng WH, Chang SK, Lim SE, Lai KS
    Cells, 2022 Sep 26;11(19).
    PMID: 36230959 DOI: 10.3390/cells11192995
    There has been a resurgence in the clinical use of polymyxin antibiotics such as colistin due to the limited treatment options for infections caused by carbapenem-resistant Enterobacterales (CRE). However, this last-resort antibiotic is currently confronted with challenges which include the emergence of chromosomal and plasmid-borne colistin resistance. Colistin resistance in Klebsiella pneumoniae is commonly caused by the mutations in the chromosomal gene mgrB. MgrB spans the inner membrane and negatively regulates PhoP phosphorylation, which is essential for bacterial outer membrane lipid biosynthesis. The present review intends to draw attention to the role of mgrB chromosomal mutations in membrane permeability in K. pneumoniae that confer colistin resistance. With growing concern regarding the global emergence of colistin resistance, deciphering physical changes of the resistant membrane mediated by mgrB inactivation may provide new insights for the discovery of novel antimicrobials that are highly effective at membrane penetration, in addition to finding out how this can help in alleviating the resistance situation.
    Matched MeSH terms: Mutation/genetics
  9. Xiao B, Deng X, Ng EY, Allen JC, Lim SY, Ahmad-Annuar A, et al.
    JAMA Neurol, 2018 01 01;75(1):127-128.
    PMID: 29131875 DOI: 10.1001/jamaneurol.2017.3363
    Matched MeSH terms: Mutation/genetics*
  10. Wu YH, Cheong LC, Meon S, Lau WH, Kong LL, Joseph H, et al.
    Arch Virol, 2013 Jun;158(6):1407-10.
    PMID: 23397332 DOI: 10.1007/s00705-013-1624-8
    A 246-nt variant of Coconut cadang-cadang viroid (CCCVd) has been identified and described from oil palms with orange spotting symptoms in Malaysia. Compared with the 246-nt form of CCCVd from coconut, the oil palm variant substituted C(31)→U in the pathogenicity domain and G(70)→C in the central conserved domain. This is the first sequence reported for a 246-nt variant of CCCVd in oil palms expressing orange spotting symptoms.
    Matched MeSH terms: Point Mutation/genetics
  11. Wolf NI, Toro C, Kister I, Latif KA, Leventer R, Pizzino A, et al.
    Neurology, 2015 Jan 20;84(3):226-30.
    PMID: 25527264 DOI: 10.1212/WNL.0000000000001157
    To describe the expanding clinical spectrum of a recently described hereditary leukoencephalopathy, hypomyelination with brainstem and spinal cord involvement and leg spasticity, which is caused by mutations in the aspartyl tRNA-synthetase encoding gene DARS, including patients with an adolescent onset.
    Matched MeSH terms: Mutation/genetics*
  12. Wei GZ, Martin KA, Xing PY, Agrawal R, Whiley L, Wood TK, et al.
    Proc Natl Acad Sci U S A, 2021 Jul 06;118(27).
    PMID: 34210797 DOI: 10.1073/pnas.2021091118
    While modulatory effects of gut microbes on neurological phenotypes have been reported, the mechanisms remain largely unknown. Here, we demonstrate that indole, a tryptophan metabolite produced by tryptophanase-expressing gut microbes, elicits neurogenic effects in the adult mouse hippocampus. Neurogenesis is reduced in germ-free (GF) mice and in GF mice monocolonized with a single-gene tnaA knockout (KO) mutant Escherichia coli unable to produce indole. External administration of systemic indole increases adult neurogenesis in the dentate gyrus in these mouse models and in specific pathogen-free (SPF) control mice. Indole-treated mice display elevated synaptic markers postsynaptic density protein 95 and synaptophysin, suggesting synaptic maturation effects in vivo. By contrast, neurogenesis is not induced by indole in aryl hydrocarbon receptor KO (AhR-/-) mice or in ex vivo neurospheres derived from them. Neural progenitor cells exposed to indole exit the cell cycle, terminally differentiate, and mature into neurons that display longer and more branched neurites. These effects are not observed with kynurenine, another AhR ligand. The indole-AhR-mediated signaling pathway elevated the expression of β-catenin, Neurog2, and VEGF-α genes, thus identifying a molecular pathway connecting gut microbiota composition and their metabolic function to neurogenesis in the adult hippocampus. Our data have implications for the understanding of mechanisms of brain aging and for potential next-generation therapeutic opportunities.
    Matched MeSH terms: Mutation/genetics
  13. Veno J, Rahman RNZRA, Masomian M, Ali MSM, Kamarudin NHA
    Molecules, 2019 Aug 30;24(17).
    PMID: 31480403 DOI: 10.3390/molecules24173169
    Thermostability remains one of the most desirable traits in many lipases. Numerous studies have revealed promising strategies to improve thermostability and random mutagenesis often leads to unexpected yet interesting findings in engineering stability. Previously, the thermostability of C-terminal truncated cold-adapted lipase from Staphylococcus epidermidis AT2 (rT-M386) was markedly enhanced by directed evolution. The newly evolved mutant, G210C, demonstrated an optimal temperature shift from 25 to 45 °C and stability up to 50 °C. Interestingly, a cysteine residue was randomly introduced on the loop connecting the two lids and accounted for the only cysteine found in the lipase. We further investigated the structural and mechanistic insights that could possibly cause the significant temperature shift. Both rT-M386 and G210C were modeled and simulated at 25 °C and 50 °C. The results clearly portrayed the effect of cysteine substitution primarily on the lid stability. Comparative molecular dynamics simulation analysis revealed that G210C exhibited greater stability than the wild-type at high temperature simulation. The compactness of the G210C lipase structure increased at 50 °C and resulted in enhanced rigidity hence stability. This observation is supported by the improved and stronger non-covalent interactions formed in the protein structure. Our findings suggest that the introduction of a single cysteine residue at the lid region of cold-adapted lipase may result in unexpected increased in thermostability, thus this approach could serve as one of the thermostabilization strategies in engineering lipase stability.
    Matched MeSH terms: Mutation/genetics*
  14. Tsai MH, Muir AM, Wang WJ, Kang YN, Yang KC, Chao NH, et al.
    Neuron, 2020 Apr 22;106(2):237-245.e8.
    PMID: 32097630 DOI: 10.1016/j.neuron.2020.01.027
    Lissencephaly (LIS), denoting a "smooth brain," is characterized by the absence of normal cerebral convolutions with abnormalities of cortical thickness. Pathogenic variants in over 20 genes are associated with LIS. The majority of posterior predominant LIS is caused by pathogenic variants in LIS1 (also known as PAFAH1B1), although a significant fraction remains without a known genetic etiology. We now implicate CEP85L as an important cause of posterior predominant LIS, identifying 13 individuals with rare, heterozygous CEP85L variants, including 2 families with autosomal dominant inheritance. We show that CEP85L is a centrosome protein localizing to the pericentriolar material, and knockdown of Cep85l causes a neuronal migration defect in mice. LIS1 also localizes to the centrosome, suggesting that this organelle is key to the mechanism of posterior predominant LIS.
    Matched MeSH terms: Mutation/genetics
  15. Tiong KH, Mohammed Yunus NA, Yiap BC, Tan EL, Ismail R, Ong CE
    PLoS One, 2014;9(1):e86230.
    PMID: 24475091 DOI: 10.1371/journal.pone.0086230
    Human cytochrome P450 2A6 (CYP2A6) is a highly polymorphic isoform of CYP2A subfamily. Our previous kinetic study on four CYP2A6 allelic variants (CYP2A6 15, CYP2A6 16, CYP2A6 21 and CYP2A6 22) have unveiled the functional significance of sequence mutations in these variants on coumarin 7-hydroxylation activity. In the present study, we further explored the ability of a typical CYP2A6 inhibitor, 8-methoxypsoralen (8-MOP), in inhibition of these alleles and we hypothesized that translational mutations in these variants are likely to give impact on 8-MOP inhibitory potency. The CYP2A6 variant and the wild type proteins were subjected to 8-MOP inhibition to yield IC50 values. In general, a similar trend of change in the IC50 and Km values was noted among the four mutants towards coumarin oxidation. With the exception of CYP2A6 16, differences in IC50 values were highly significant which implied compromised interaction of the mutants with 8-MOP. Molecular models of CYP2A6 were subsequently constructed and ligand-docking experiments were performed to rationalize experimental data. Our docking study has shown that mutations have induced enlargement of the active site volume in all mutants with the exception of CYP2A6 16. Furthermore, loss of hydrogen bond between 8-MOP and active site residue Asn297 was evidenced in all mutants. Our data indicate that the structural changes elicited by the sequence mutations could affect 8-MOP binding to yield differential enzymatic activities in the mutant CYP2A6 proteins.
    Matched MeSH terms: Mutation/genetics
  16. Thong MK, Tan JA, Tan KL, Yap SF
    J Trop Pediatr, 2005 Dec;51(6):328-33.
    PMID: 15967770 DOI: 10.1093/tropej/fmi052
    beta-thalassaemia major, an autosomal recessive hemoglobinopathy, is one of the most common single gene disorders in multi-racial Malaysia. The control of beta-thalassaemia major requires a multi-disciplinary approach that includes population screening, genetic counselling, prenatal diagnosis and the option of termination of affected pregnancies. To achieve this objective, the molecular characterisation of the spectrum of beta-globin gene mutations in each of the affected ethnic groups is required. We studied 88 consecutive unrelated individuals and their respective families with beta-thalassaemia (74 beta-thalassaemia major, 12 HbE-beta-thalassaemia, 2 with HbE homozygotes) and four individuals with beta-thalassaemia trait that contributed a total 180 alleles for study. Using a 2-step molecular diagnostic strategy consisting of amplification refractory mutation system (ARMS) to identify the 8 most common mutations followed by other DNA-based diagnostic techniques, a total of 177 (98.3 per cent) of the 180 beta-thalassaemia alleles were characterised. One out of 91 (1 per cent) of the Chinese alleles, one out of 46 (2.2 per cent) Malay alleles and one out of two Indian alleles remained unknown. A 100 per cent success rate was achieved in studying the Kadazandusun community in this study. A strategy to identify beta-globin gene mutations in Malaysians with beta-thalassaemia is proposed based on this outcome.
    Matched MeSH terms: Mutation/genetics*
  17. Thevarajah M, Nadzimah MN, Chew YY
    Clin Biochem, 2009 Mar;42(4-5):430-4.
    PMID: 19026622 DOI: 10.1016/j.clinbiochem.2008.10.015
    Glycated hemoglobin, measured as HbA1c is used as an index of mean glycemia in diabetic patients over the preceding 2-3 months. Various assay methods are used to measure HbA1c and many factors may interfere with its measurement according to assay method used, causing falsely high or low results.
    Matched MeSH terms: Mutation/genetics*
  18. Tay YW, Tan AH, Lim JL, Lohmann K, Ibrahim KA, Abdul Aziz Z, et al.
    Parkinsonism Relat Disord, 2023 Jun;111:105399.
    PMID: 37209484 DOI: 10.1016/j.parkreldis.2023.105399
    BACKGROUND: About 5-10% of Parkinson's disease (PD) cases are early onset (EOPD), with several genes implicated, including GBA1, PRKN, PINK1, and SNCA. The spectrum and frequency of mutations vary across populations and globally diverse studies are crucial to comprehensively understand the genetic architecture of PD. The ancestral diversity of Southeast Asians offers opportunities to uncover a rich PD genetics landscape, and identify common regional mutations and new pathogenic variants.

    OBJECTIVES: This study aimed to investigate the genetic architecture of EOPD in a multi-ethnic Malaysian cohort.

    METHODS: 161 index patients with PD onset ≤50 years were recruited from multiple centers across Malaysia. A two-step approach to genetic testing was used, combining a next-generation sequencing-based PD gene panel and multiplex ligation-dependent probe amplification (MLPA).

    RESULTS: Thirty-five patients (21.7%) carried pathogenic or likely pathogenic variants involving (in decreasing order of frequency): GBA1, PRKN, PINK1, DJ-1, LRRK2, and ATP13A2. Pathogenic/likely pathogenic variants in GBA1 were identified in thirteen patients (8.1%), and were also commonly found in PRKN and PINK1 (11/161 = 6.8% and 6/161 = 3.7%, respectively). The overall detection rate was even higher in those with familial history (48.5%) or age of diagnosis ≤40 years (34.8%). PRKN exon 7 deletion and the PINK1 p.Leu347Pro variant appear to be common among Malay patients. Many novel variants were found across the PD-related genes.

    CONCLUSIONS: This study provides novel insights into the genetic architecture of EOPD in Southeast Asians, expands the genetic spectrum in PD-related genes, and highlights the importance of diversifying PD genetic research to include under-represented populations.

    Matched MeSH terms: Mutation/genetics
  19. Tan LL, Lau TY, Timothy W, Prabakaran D
    ScientificWorldJournal, 2014;2014:935846.
    PMID: 25574497 DOI: 10.1155/2014/935846
    Chloroquine resistance (CQR) in falciparum malaria was identified to be associated with several mutations in the chloroquine resistance transporter gene (pfcrt) that encodes the transmembrane transporter in digestive vacuole membrane of the parasite. This study aimed to investigate the point mutations across the full-length pfcrt in Plasmodium falciparum isolates in Sabah, Malaysia. A total of 31 P. falciparum positive samples collected from Keningau, Kota Kinabalu, and Kudat, Sabah, were analyzed. pfcrt was PCR amplified and cloned prior to sequence analysis. This study showed that all the previously described 10 point mutations associated with CQR at codons 72, 74, 75, 76, 97, 220, 271, 326, 356, and 371 were found with different prevalence. Besides, two novel point mutations, I166V and H273N, were identified with 22.5% and 19.3%, respectively. Three haplotypes, namely, CVMNK (29%), CVIET (3.2%), and SVMNT (67.7%), were identified. High prevalence of SVMNT among P. falciparum isolates from Sabah showed that these isolates are closer to the P. falciparum isolates from Papua New Guinea rather than to the more proximal Southeast Asian CVIET haplotype. Full-length analysis of pfcrt showed that chloroquine resistant P. falciparum in Sabah is still prevalent despite the withdrawal of chloroquine usage since 1979.
    Matched MeSH terms: Point Mutation/genetics
  20. Tan KL, Tan JA, Wong YC, Wee YC, Thong MK, Yap SF
    Genet. Test., 2001;5(1):17-22.
    PMID: 11336396 DOI: 10.1089/109065701750168626
    Beta-thalassemia major patients have chronic anemia and are dependent on blood transfusions to sustain life. Molecular characterization and prenatal diagnosis of beta3-thalassemia is essential in Malaysia because about 4.5% of the population are heterozygous carriers for beta-thalassemia. The high percentage of compound heterozygosity (47.62%) found in beta-thalassemia major patients in the Thalassaemia Registry, University of Malaya Medical Centre (UMMC), Malaysia, also supports a need for rapid, economical, and sensitive protocols for the detection of beta-thalassemia mutations. Molecular characterization of beta-thalassemia mutations in Malaysia is currently carried out using ARMS, which detects a single beta-thalassemia mutation per PCR reaction. We developed and evaluated Combine amplification refractory mutation system (C-ARMS) techniques for efficient molecular detection of two to three beta-thalassemia mutations in a single PCR reaction. Three C-ARMS protocols were evaluated and established for molecular characterization of common beta-thalassemia mutations in the Malay and Chinese ethnic groups in Malaysia. Two C-ARMS protocols (cd 41-42/IVSII #654 and -29/cd 71-72) detected the beta-thalassemia mutations in 74.98% of the Chinese patients studied. The CARMS for cd 41-42/IVSII #654 detected beta-thalassemia mutations in 72% of the Chinese families. C-ARMS for cd 41-42/IVSI #5/cd 17 allowed detection of beta-thalassemia mutations in 36.53% of beta-thalassemia in the Malay patients. C-ARMS for cd 41-42/IVSI #5/cd 17 detected beta-thalassemia in 45.54% of the Chinese patients. We conclude that C-ARMS with the ability to detect two to three mutations in a single reaction provides more rapid and cost-effective protocols for beta-thalassemia prenatal diagnosis and molecular analysis programs in Malaysia.
    Matched MeSH terms: Mutation/genetics*
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