H. M. Asif

Current trends in chloroplast genome research

Chloroplast is an important cellular organelle of autotrophs which has an independent, circular, doublestranded DNA molecule termed as chloroplast genome. The chloroplast DNA (cpDNA) contains essential genes for its maintenance and operation. Several components of the photosystems and proteins involved in biosynthetic pathways are also encoded by the chloroplast genome. Exploring the genetic repository of this organelle is vital due to its conserved nature, small size, persistent gene organization and promising ability for transgenic expression. Therefore, cpDNA sequence information has been instrumental in phylogenetic studies and molecular taxonomy of plants. Chloroplast genome sequencing efforts have being initiated with conventional cloning and chain-termination sequencing technologies. Dedicated databases such as CGDB and GOBASE among others have been established as more and more complete cpDNA sequences are being reported. Presently, elegant molecular biology techniques including shotgun sequencing, rolling circle amplification (RCA), Amplification, Sequencing and Annotation of Plasteome (ASAP) and Next generation sequencing are being used to accelerate data output. Owing to many fold increase in submission of cpDNA sequences in nucleotide databases, challenges of in-depth data analysis stimulated the emergence of devoted annotation, assembling and phylogenetic software. Recently, reported bioinformatics software for chloroplast genome studies comprise of DOGMA for annotation, SCAN-SE, ARAGON and PREP suit for RNA analyses and CG viewer for circular map construction/comparative analysis. Faster algorithms for gene-order based phylogenetic reconstruction and bootstrap analysis have attracted the attention of research community. Current trends in sequencing strategies and bioinformatics with reference to chloroplast genomes hold great potential to illuminate more hidden corners of this ancient cell organelle.

Complete genome sequencing and variant analysis of a Pakistani individual

We sequenced the genome of a Pakistani male at 25.5x coverage using massively parallel sequencing technology. More than 90% of the sequence reads were mapped to the human reference genome. In subsequent analysis, we identified 3 224 311 single-nucleotide polymorphisms (SNPs), of which 388 532 (12% of the total SNPs) had not been previously recorded in single nucleotide polymorphism database (dbSNP) or the 1000 Genomes Project database. The 5991 non-synonymous coding variants were screened for deleterious or disease-associated SNPs. Analysis of genes with deleterious SNPs identified ‘retinoic acid signaling’ and ‘regulation of transcription’ as the enriched Gene Ontology terms. Scanning of non-synonymous SNPs against the OMIM revealed several disease and phenotype-associated variants in Pakistani genome. Comparative analysis with Indian genome sequence revealed >1.8 million shared SNPs; 32% of which were annotated in ∼14 000 genes. Gene Ontology (GO) terms analysis of these genes identified ‘response to jasmonic acid stimulus’, ‘aminoglycoside antibiotic metabolic process’ and ‘glycoside metabolic process’ with considerable enrichment. A total of 59 558 of small indels (1–5 bp) and 16 063 large structural variations were found; 54% of which was novel. Substantial number of novel structural variations discovered in Pakistani genome enforced previous inferences that (a) structural variations are major type of variation in the genome and (b) compared with SNPs, they putatively exhibit equivalent or superior functional roles. This genome sequence information will be an important reference for population-wide genomics studies of ethnically diverse South Asian subcontinent.

Genome characterization of a novel Burkholderia cepacia complex genomovar isolated from dieback affected mango orchards

We characterized the genome of the antibiotic resistant, caseinolytic and non-hemolytic Burkholderia sp. strain TJI49, isolated from mango trees (Mangifera indica L.) with dieback disease. This isolate produced severe disease symptoms on the indicator plants. Next generation DNA sequencing and short-read assembly generated the 60X deep 7,631,934 nucleotide draft genome of Burkholderia sp. TJI49 which comprised three chromosomes and at least one mega plasmid. Genome annotation studies revealed a total 8,992 genes, out of which 8,940 were protein coding genes. Comparative genomics and phylogenetics identified Burkholderia sp. TJI49 as a distinct species of Burkholderia cepacia complex (BCC), closely related to B.multivorans ATCC17616. Genome-wide sequence alignment of this isolate with replicons of BCC members showed conservation of core function genes but considerable variations in accessory genes. Subsystem-based gene annotation identified the active presence of wide spread colonization island and type VI secretion system in Burkholderia sp. TJI49. Sequence comparisons revealed (a) 28 novel ORFs that have no database matches and (b) 23 ORFs with orthologues in species other than Burkholderia, indicating horizontal gene transfer events. Fold recognition of novel ORFs identified genes encoding pertactin autotransporter-like proteins (a constituent of type V secretion system) and Hap adhesion-like proteins (involved in cell–cell adhesion) in the genome of Burkholderia sp. TJI49. The genomic characterization of this isolate provided additional information related to the ‘pan-genome’ of Burkholderia species.

Revisiting antithrombotic therapeutics; sculptin, a novel specific, competitive, reversible, scissile and tight binding inhibitor of thrombin

Thrombin is a multifunctional enzyme with a key role in the coagulation cascade. Its functional modulation can culminate into normal blood coagulation or thrombosis. Thus, the identification of novel potent inhibitors of thrombin are of immense importance. Sculptin is the first specific thrombin inhibitor identified in the transcriptomics analysis of tick’s salivary glands. It consists of 168 residues having four similar repeats and evolutionary diverged from hirudin. Sculptin is a competitive, specific and reversible inhibitor of thrombin with a Ki of 18.3 ± 1.9 pM (kon 4.04 ± 0.03 × 107 M−1 s−1 and koff 0.65 ± 0.04 × 10−3 s−1). It is slowly consumed by thrombin eventually losing its activity. Contrary, sculptin is hydrolyzed by factor Xa and each polypeptide fragment is able to inhibit thrombin independently. A single domain of sculptin alone retains ~45% of inhibitory activity, which could bind thrombin in a bivalent fashion. The formation of a small turn/helical-like structure by active site binding residues of sculptin might have made it a more potent thrombin inhibitor. In addition, sculptin prolongs global coagulation parameters. In conclusion, sculptin and its independent domain(s) have strong potential to become novel antithrombotic therapeutics.

Expanding the clinical and genetic spectrum of G6PD deficiency: The occurrence of BCGitis and novel missense mutation

Glucose-6-phosphate dehydrogenase (G6PD) is a key enzyme in the pentose phosphate pathway that ensures sufficient production of coenzyme nicotinamide adenine dinucleotide phosphate (NADPH) by catalyzing the reduction of NADP+ to NADPH. Noteworthy, the latter mediates the production of reactive oxygen species (ROS) by phagocytic cells such as neutrophils and monocytes. Therefore, patients with severe forms of G6PD deficiency may present impaired NADPH oxidase activity and become susceptible to recurrent infections. This fact, highlights the importance to characterize the immunopathologic mechanisms underlying the susceptibility to infections in patients with G6PD deficiency. Here we report the first two cases of G6PD deficiency with Bacille Calmette-Guérin (BCG) adverse effect, besides jaundice, hemolytic anemia and recurrent infections caused by Staphylococcus aureus. The qualitative G6PD screening was performed and followed by oxidative burst analysis using flow cytometry. Genetic and in silico analyses were carried out by Sanger sequencing and mutation pathogenicity predicted using bioinformatics tools, respectively. Activated neutrophils and monocytes from patients displayed impaired oxidative burst. The genetic analysis revealed the novel missense mutation c.1157T>A/p.L386Q in G6PD. In addition, in silico analysis indicated that this mutation is pathogenic, thereby hampering the oxidative burst of neutrophils and monocytes from patients. Our data expand the clinical and genetic spectrum of G6PD deficiency, and suggest that impaired oxidative burst in this severe primary immune deficiency is an underlying immunopathologic mechanism that predisposes to mycobacterial infections.

Drugs Targeting SNPrs35753505 of the NRG1 Gene May Prevent the Association of Neurological Disorder Schizophrenia in a Pakistani Population

The Neuregulin 1 (NRG1) gene has been associated with schizophrenia in several populations, and all four types of NRG1 genes are linked with neurotransmitters activities. In this study for the first time we have demonstrated an association between NRG1 mutation and schizophrenia in Pakistani population. We examined the relationship of three genetic variants SNPs: rs3924999, rs2954041 and rs35753505 of NRG1 gene with the onset of disease. Genomic DNA samples were obtained from the blood of 100 patients and 80 matched controls. All three NRG1 SNPs were genotyped by polymerase chain reaction-restriction fragment length polymorphism method and further confirmed by DNA sequencing. The SNPs frequencies were estimated by Hardy-Weinberg equilibrium and Chi-square tests. Our study established a significant association of rs35753505 with schizophrenia but no association with rs3924999 and rs2954041. The frequency of risk allele C was significantly higher (62.5%) in rs35753505 patients when compared to controls (28.13%). Genotype frequency by Hardy-Weinberg equilibrium for SNPrs3924999 in patients was GG 77.4%, GA 21.12% and AA 1.44% and showed no association with the disease. Similarly, no genotype association was observed in rs2954041: GG 92.98%, GT 6.89%, TT 0.13% of NRG1. However, one unexpected G allele, 100% guanine (G) with no adenine (A) was found to be present in SNP rs35753505 in both patients and controls. This is an interesting finding that both cohorts display only allele G peak but no peak for allele A in the electropherogram for this SNP. Our results suggest that SNP rs35753505 of NRG1 plays an important role in conferring susceptibility to the schizophrenia in a Pakistani population.

Comparative genomics of an endophytic Pseudomonas putida isolated from mango orchard

Abstract We analyzed the genome sequence of an endophytic bacterial strain Pseudomonas putida TJI51 isolated from mango bark tissues. Next generation DNA sequencing and short read de novo assembly generated the 5,805,096 bp draft genome of P. putida TJI51. Out of 6,036 protein coding genes in P. putida TJI51 sequences, 4,367 (72%) were annotated with functional specifications, while the remaining encoded hypothetical proteins. Comparative genome sequence analysis revealed that the P. putida TJI51genome contains several regions, not identified in so far sequenced P. putida genomes. Some of these regions were predicted to encode enzymes, including acetylornithine deacetylase, betaine aldehyde dehydrogenase, aldehyde dehydrogenase, benzoylformate decarboxylase, hydroxyacylglutathione hydrolase, and uroporphyrinogen decarboxylase. The genome of P. putida TJI51 contained three nonribosomal peptide synthetase gene clusters. Genome sequence analysis of P. putidaTJI51 identified this bacterium as an endophytic resident. The endophytic fitness might be linked with alginate, which facilitates bacterial colonization in plant tissues. Genome sequence analysis shed light on the presence of a diverse spectrum of metabolic activities and adaptation of this isolate to various niches.