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Fulltext Computational discovery and RT-PCR validation of novel Burkholderia conserved and Burkholderia pseudomallei unique sRNAs

Khoo JS, Chai SF, Mohamed R, Nathan S, Firdaus-Raih M

BMC Genomics, 2012;13 Suppl 7:S13.
PMID: 23282220 DOI: 10.1186/1471-2164-13-S7-S13

The sRNAs of bacterial pathogens are known to be involved in various cellular roles including environmental adaptation as well as regulation of virulence and pathogenicity. It is expected that sRNAs may also have similar functions for Burkholderia pseudomallei, a soil bacterium that can adapt to diverse environmental conditions, which causes the disease melioidosis and is also able to infect a wide variety of hosts.
Fulltext Whole-genome comparative analysis of Malaysian Burkholderia pseudomallei clinical isolates

Ghazali AK, Eng SA, Khoo JS, Teoh S, Hoh CC, Nathan S

Microb Genom, 2021 02;7(2).
PMID: 33565959 DOI: 10.1099/mgen.0.000527

Burkholderia pseudomallei, a soil-dwelling Gram-negative bacterium, is the causative agent of the endemic tropical disease melioidosis. Clinical manifestations of B. pseudomallei infection range from acute or chronic localized infection in a single organ to fulminant septicaemia in multiple organs. The diverse clinical manifestations are attributed to various factors, including the genome plasticity across B. pseudomallei strains. We previously characterized B. pseudomallei strains isolated in Malaysia and noted different levels of virulence in model hosts. We hypothesized that the difference in virulence might be a result of variance at the genome level. In this study, we sequenced and assembled four Malaysian clinical B. pseudomallei isolates, UKMR15, UKMPMC2000, UKMD286 and UKMH10. Phylogenomic analysis showed that Malaysian subclades emerged from the Asian subclade, suggesting that the Malaysian strains originated from the Asian region. Interestingly, the low-virulence strain, UKMH10, was the most distantly related compared to the other Malaysian isolates. Genomic island (GI) prediction analysis identified a new island of 23 kb, GI9c, which is present in B. pseudomallei and Burkholderia mallei, but not Burkholderia thailandensis. Genes encoding known B. pseudomallei virulence factors were present across all four genomes, but comparative analysis of the total gene content across the Malaysian strains identified 104 genes that are absent in UKMH10. We propose that these genes may encode novel virulence factors, which may explain the reduced virulence of this strain. Further investigation on the identity and role of these 104 proteins may aid in understanding B. pseudomallei pathogenicity to guide the design of new therapeutics for treating melioidosis.
RNA-Seq transcriptome profiling of Nile rat livers reveals novel insights on the anti-diabetic mechanisms of Water-Soluble Palm Fruit Extract

Leow SS, Khoo JS, Lee WK, Hoh CC, Fairus S, Sambanthamurthi R, et al.

J Appl Genet, 2024 Dec;65(4):867-895.
PMID: 38890243 DOI: 10.1007/s13353-024-00880-1

Water-Soluble Palm Fruit Extract (WSPFE) has been shown to confer anti-diabetic effects in the Nile rat (NR) (Arvicanthis niloticus). Liquid and powder WSPFE both deterred diabetes onset in NRs fed a high-carbohydrate (hiCHO) diet, but the liquid form provided better protection. In this study, NRs were fed either a hiCHO diet or the same diet added with liquid or powder WSPFE. Following feeding of the diets for 8 weeks, random blood glucose levels were measured to categorize NRs as either diabetes-resistant or diabetes-susceptible, based on a cut-off value of 75 mg/dL. Livers were then obtained for Illumina HiSeq 4000 paired end RNA-sequencing (RNA-Seq) and the data were mapped to the reference genome. Consistent with physiological and biochemical parameters, the gene expression data obtained indicated that WSPFE was associated with protection against diabetes. Among hepatic genes upregulated by WSPFE versus controls, were genes related to insulin-like growth factor binding protein, leptin receptor, and processes of hepatic metabolism maintenance, while those downregulated were related to antigen binding, immunoglobulin receptor, inflammation- and cancer-related processes. WSPFE supplementation thus helped inhibit diabetes progression in NRs by increasing insulin sensitivity and reducing both the inflammatory effects of a hiCHO diet and the related DNA-damage compensatory mechanisms contributing to liver disease progression. In addition, the genetic permissiveness of susceptible NRs to develop diabetes was potentially associated with dysregulated compensatory mechanisms involving insulin signaling and oxidative stress over time. Further studies on other NR organs associated with diabetes and its complications are warranted.
Identification of reference genes for real-time polymerase chain reaction gene expression studies in Nile rats fed Water-Soluble Palm Fruit Extract

Leow SS, Lee WK, Khoo JS, Teoh S, Hoh CC, Fairus S, et al.

Mol Biol Rep, 2020 Dec;47(12):9409-9427.
PMID: 33222119 DOI: 10.1007/s11033-020-06003-3

The Nile rat (Arvicanthis niloticus) is a novel diurnal carbohydrate-sensitive rodent useful for studies on type 2 diabetes mellitus (T2DM) and the metabolic syndrome. Hepatic responses to T2DM and any interventions thereof can be evaluated via transcriptomic gene expression analysis. However, the study of gene expression via real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) requires identification of stably expressed reference genes for accurate normalisation. This study describes the evaluation and identification of stable reference genes in the livers from Control Nile rats as well as those supplemented with Water-Soluble Palm Fruit Extract, which has been previously shown to attenuate T2DM in this animal model. Seven genes identified as having stable expression in RNA-Sequencing transcriptome analysis were chosen for verification using real-time RT-qPCR. Six commonly used reference genes from previous literature and two genes from a previous microarray gene expression study in Nile rats were also evaluated. The expression data of these 15 candidate reference genes were analysed using the RefFinder software which incorporated analyses performed by various algorithms. The Hpd, Pnpla6 and Vpp2 genes were identified as the most stable across the 36 samples tested. Their applicability was demonstrated through the normalisation of the gene expression profiles of two target genes, Cela1 and Lepr. In conclusion, three novel reference genes which can be used for robust normalisation of real-time RT-qPCR data were identified, thereby facilitating future hepatic gene expression studies in the Nile rat.
Fulltext Exome sequencing identifies SLC26A4, GJB2, SCARB2 and DUOX2 mutations in 2 siblings with Pendred syndrome in a Malaysian family

Chow YP, Abdul Murad NA, Mohd Rani Z, Khoo JS, Chong PS, Wu LL, et al.

Orphanet J Rare Dis, 2017 Feb 21;12(1):40.
PMID: 28222800 DOI: 10.1186/s13023-017-0575-7

BACKGROUND: Pendred syndrome (PDS, MIM #274600) is an autosomal recessive disorder characterized by congenital sensorineural hearing loss and goiter. In this study, we describing the possible PDS causal mutations in a Malaysian family with 2 daughters diagnosed with bilateral hearing loss and hypothyroidism.
METHODS AND RESULTS: Whole exome sequencing was performed on 2 sisters with PDS and their unaffected parents. Our results showed that both sisters inherited monoallelic mutations in the 2 known PDS genes, SLC26A4 (ENST00000265715:c.1343C > T, p.Ser448Leu) and GJB2 (ENST00000382844:c.368C > A, p.Thr123Asn) from their father, as well as another deafness-related gene, SCARB2 (ENST00000264896:c.914C > T, p.Thr305Met) from their mother. We postulated that these three heterozygous mutations in combination may be causative to deafness, and warrants further investigation. Furthermore, we also identified a compound heterozygosity involving the DUOX2 gene (ENST00000603300:c.1588A > T:p.Lys530* and c.3329G > A:p.Arg1110Gln) in both sisters which are inherited from both parents and may be correlated with early onset of goiter. All the candidate mutations were predicted deleterious by in silico tools.
CONCLUSIONS: In summary, we proposed that PDS in this family could be a polygenic disorder which possibly arises from a combination of heterozygous mutations in SLC26A4, GJB2 and SCARB2 which associated with deafness, as well as compound heterozygous DUOX2 mutations which associated with thyroid dysfunction.
Fulltext Genome Analysis of the First Extensively Drug-Resistant (XDR) Mycobacterium tuberculosis in Malaysia Provides Insights into the Genetic Basis of Its Biology and Drug Resistance

Kuan CS, Chan CL, Yew SM, Toh YF, Khoo JS, Chong J, et al.

PLoS One, 2015;10(6):e0131694.
PMID: 26110649 DOI: 10.1371/journal.pone.0131694

The outbreak of extensively drug-resistant tuberculosis (XDR-TB) has become an increasing problem in many TB-burdened countries. The underlying drug resistance mechanisms, including the genetic variation favored by selective pressure in the resistant population, are partially understood. Recently, the first case of XDR-TB was reported in Malaysia. However, the detailed genotype family and mechanisms of the formation of multiple drugs resistance are unknown. We sequenced the whole genome of the UM 1072388579 strain with a 2-kb insert-size library and combined with that from previously sequenced 500-bp-insert paired-end reads to produce an improved sequence with maximal sequencing coverage across the genome. In silico spoligotyping and phylogenetic analyses demonstrated that UM 1072388579 strain belongs to an ancestral-like, non-Beijing clade of East Asia lineage. This is supported by the presence of a number of lineage-specific markers, including fadD28, embA, nuoD and pks7. Polymorphism analysis showed that the drug-susceptibility profile is correlated with the pattern of resistance mutations. Mutations in drug-efflux pumps and the cell wall biogenesis pathway such as mmpL, pks and fadD genes may play an important role in survival and adaptation of this strain to its surrounding environment. In this work, fifty-seven putative promoter SNPs were identified. Among them, we identified a novel SNP located at -4 T allele of TetR/acrR promoter as an informative marker to recognize strains of East Asian lineage. Our work indicates that the UM 1072388579 harbors both classical and uncommon SNPs that allow it to escape from inhibition by many antibiotics. This study provides a strong foundation to dissect the biology and underlying resistance mechanisms of the first reported XDR M. tuberculosis in Malaysia.
Fulltext Genomic insight into pathogenicity of dematiaceous fungus Corynespora cassiicola

Looi HK, Toh YF, Yew SM, Na SL, Tan YC, Chong PS, et al.

PeerJ, 2017;5:e2841.
PMID: 28149676 DOI: 10.7717/peerj.2841

Corynespora cassiicola is a common plant pathogen that causes leaf spot disease in a broad range of crop, and it heavily affect rubber trees in Malaysia (Hsueh, 2011; Nghia et al., 2008). The isolation of UM 591 from a patient's contact lens indicates the pathogenic potential of this dematiaceous fungus in human. However, the underlying factors that contribute to the opportunistic cross-infection have not been fully studied. We employed genome sequencing and gene homology annotations in attempt to identify these factors in UM 591 using data obtained from publicly available bioinformatics databases. The assembly size of UM 591 genome is 41.8 Mbp, and a total of 13,531 (≥99 bp) genes have been predicted. UM 591 is enriched with genes that encode for glycoside hydrolases, carbohydrate esterases, auxiliary activity enzymes and cell wall degrading enzymes. Virulent genes comprising of CAZymes, peptidases, and hypervirulence-associated cutinases were found to be present in the fungal genome. Comparative analysis result shows that UM 591 possesses higher number of carbohydrate esterases family 10 (CE10) CAZymes compared to other species of fungi in this study, and these enzymes hydrolyses wide range of carbohydrate and non-carbohydrate substrates. Putative melanin, siderophore, ent-kaurene, and lycopene biosynthesis gene clusters are predicted, and these gene clusters denote that UM 591 are capable of protecting itself from the UV and chemical stresses, allowing it to adapt to different environment. Putative sterigmatocystin, HC-toxin, cercosporin, and gliotoxin biosynthesis gene cluster are predicted. This finding have highlighted the necrotrophic and invasive nature of UM 591.
Bursal transcriptome profiling of different inbred chicken lines reveals key differentially expressed genes at 3 days post-infection with very virulent infectious bursal disease virus

Farhanah MI, Yasmin AR, Mat Isa N, Hair-Bejo M, Ideris A, Powers C, et al.

J Gen Virol, 2018 Jan;99(1):21-35.
PMID: 29058656 DOI: 10.1099/jgv.0.000956

Infectious bursal disease is a highly contagious disease in the poultry industry and causes immunosuppression in chickens. Genome-wide regulations of immune response genes of inbred chickens with different genetic backgrounds, following very virulent infectious bursal disease virus (vvIBDV) infection are poorly characterized. Therefore, this study aims to analyse the bursal tissue transcriptome of six inbred chicken lines 6, 7, 15, N, O and P following infection with vvIBDV strain UK661 using strand-specific next-generation sequencing, by highlighting important genes and pathways involved in the infected chicken during peak infection at 3 days post-infection. All infected chickens succumbed to the infection without major variations among the different lines. However, based on the viral loads and bursal lesion scoring, lines P and 6 can be considered as the most susceptible lines, while lines 15 and N were regarded as the least affected lines. Transcriptome profiling of the bursa identified 4588 genes to be differentially expressed, with 2985 upregulated and 1642 downregulated genes, in which these genes were commonly or uniquely detected in all or several infected lines. Genes that were upregulated are primarily pro-inflammatory cytokines, chemokines and IFN-related. Various genes that are associated with B-cell functions and genes related to apoptosis were downregulated, together with the genes involved in p53 signalling. In conclusion, bursal transcriptome profiles of different inbred lines showed differential expressions of pro-inflammatory cytokines and chemokines, Th1 cytokines, JAK-STAT signalling genes, MAPK signalling genes, and their related pathways following vvIBDV infection.
Fulltext Expression of fatty acid and triacylglycerol synthesis genes in interspecific hybrids of oil palm

Ting NC, Sherbina K, Khoo JS, Kamaruddin K, Chan PL, Chan KL, et al.

Sci Rep, 2020 10 01;10(1):16296.
PMID: 33004875 DOI: 10.1038/s41598-020-73170-5

Evaluation of transcriptome data in combination with QTL information has been applied in many crops to study the expression of genes responsible for specific phenotypes. In oil palm, the mesocarp oil extracted from E. oleifera × E. guineensis interspecific hybrids is known to have lower palmitic acid (C16:0) content compared to pure African palms. The present study demonstrates the effectiveness of transcriptome data in revealing the expression profiles of genes in the fatty acid (FA) and triacylglycerol (TAG) biosynthesis processes in interspecific hybrids. The transcriptome assembly yielded 43,920 putative genes of which a large proportion were homologous to known genes in the public databases. Most of the genes encoding key enzymes involved in the FA and TAG synthesis pathways were identified. Of these, 27, including two candidate genes located within the QTL associated with C16:0 content, showed differential expression between developmental stages, populations and/or palms with contrasting C16:0 content. Further evaluation using quantitative real-time PCR revealed that differentially expressed patterns are generally consistent with those observed in the transcriptome data. Our results also suggest that different isoforms are likely to be responsible for some of the variation observed in FA composition of interspecific hybrids.
Whole genome sequencing of Malaysian colorectal cancer patients reveals specific druggable somatic mutations

Mohd Yunos RI, Ab Mutalib NS, Khoo JS, Saidin S, Ishak M, Syafruddin SE, et al.

Front Mol Biosci, 2022;9:997747.
PMID: 36866106 DOI: 10.3389/fmolb.2022.997747

The incidences of colorectal cancer (CRC) are continuously increasing in some areas of the world, including Malaysia. In this study, we aimed to characterize the landscape of somatic mutations using the whole-genome sequencing approach and identify druggable somatic mutations specific to Malaysian patients. Whole-genome sequencing was performed on the genomic DNA obtained from 50 Malaysian CRC patients' tissues. We discovered the top significantly mutated genes were APC, TP53, KRAS, TCF7L2 and ACVR2A. Four novel, non-synonymous variants were identified in three genes, which were KDM4E, MUC16 and POTED. At least one druggable somatic alteration was identified in 88% of our patients. Among them were two frameshift mutations in RNF43 (G156fs and P192fs) predicted to have responsive effects against the Wnt pathway inhibitor. We found that the exogenous expression of this RNF43 mutation in CRC cells resulted in increased cell proliferation and sensitivity against LGK974 drug treatment and G1 cell cycle arrest. In conclusion, this study uncovered our local CRC patients' genomic landscape and druggable alterations. It also highlighted the role of specific RNF43 frameshift mutations, which unveil the potential of an alternative treatment targeting the Wnt/β-Catenin signalling pathway and could be beneficial, especially to Malaysian CRC patients.

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