Rubina Tabassum Siddiqui

Distribution of common genetic subgroups in childhood acute lymphoblastic leukemia in four developing countries

An international project was conducted to identify the common acute lymphoblastic leukemia (ALL)-specific fusion genes (ETV6-RUNX1,MLL-AF4,TCF3-PBX1, and BCR-ABL1) in developing countries to provide additional prognostic information at diagnosis. A total of 181 children with newly diagnosed ALL were tested by reverse transcriptase-polymerase chain reaction at laboratories in India, Pakistan, Myanmar, and Sudan, following a common protocol. To our knowledge, this report is novel in its report from these countries, except India. Across the four countries, the ETV6-RUNX1 (TEL-AML1) fusion gene was present in only 5% of cases. All the positive samples were from children aged 1 to 10 years, in whom the prevalence of this fusion gene, which is associated with good prognosis, was 7.4% (9 out of 121 samples), a much lower rate than reported from Western populations. In the 18 ALL cases tested in Sudan, a notable excess of MLL-AF4 (17%) and BCR-ABL1 (22%) fusion genes was found. This study highlights the need for wider international surveys of the molecular epidemiology of ALL.

Two different point mutations in ABL gene ATP-binding domain conferring Primary Imatinib resistance in a Chronic Myeloid Leukemia (CML) patient: A case report

Imatinib (Gleevec) is the effective therapy for BCR-ABL positive CML patients. Point mutations have been detected in ATP-binding domain of ABL gene which disturbs the binding of Gleevec to this target leading to resistance. Detection of mutations is helpful in clinical management of imatinib resistance. We established a very sensitive (ASO) PCR to detect mutations in an imatinib-resistant CML patient. Mutations C944T and T1052C were detected which cause complete partial imatinib resistance, respectively. This is the first report of multiple point mutations conferring primary imatinib resistance in same patient at the same time. Understanding the biological reasons of primary imatinib resistance is one of the emerging issues of pharmacogenomics and will be helpful in understanding primary resistance of molecularly-targeted cancer therapies. It will also be of great utilization in clinical management of imatinib resistance. Moreover, this ASO-PCR assay is very effective in detecting mutations related to imatinib resistance.

Genomics and Machine Learning for Taxonomy Consensus: The Mycobacterium tuberculosis Complex Paradigm

Infra-species taxonomy is a prerequisite to compare features such as virulence in different pathogen lineages. Mycobacterium tuberculosis complex taxonomy has rapidly evolved in the last 20 years through intensive clinical isolation, advances in sequencing and in the description of fast-evolving loci (CRISPR and MIRU-VNTR). On-line tools to describe new isolates have been set up based on known diversity either on CRISPRs (also known as spoligotypes) or on MIRU-VNTR profiles. The underlying taxonomies are largely concordant but use different names and offer different depths. The objectives of this study were 1) to explicit the consensus that exists between the alternative taxonomies, and 2) to provide an on-line tool to ease classification of new isolates. Genotyping (24-VNTR, 43-spacers spoligotypes, IS6110-RFLP) was undertaken for 3,454 clinical isolates from the Netherlands (2004-2008). The resulting database was enlarged with African isolates to include most human tuberculosis diversity. Assignations were obtained using TB-Lineage, MIRU-VNTRPlus, SITVITWEB and an algorithm from Borile et al. By identifying the recurrent concordances between the alternative taxonomies, we proposed a consensus including 22 sublineages. Original and consensus assignations of the all isolates from the database were subsequently implemented into an ensemble learning approach based on Machine Learning tool Weka to derive a classification scheme. All assignations were reproduced with very good sensibilities and specificities. When applied to independent datasets, it was able to suggest new sublineages such as pseudo-Beijing. This Lineage Prediction tool, efficient on 15-MIRU, 24-VNTR and spoligotype data is available on the web interface “TBminer.” Another section of this website helps summarizing key molecular epidemiological data, easing tuberculosis surveillance. Altogether, we successfully used Machine Learning on a large dataset to set up and make available the first consensual taxonomy for human Mycobacterium tuberculosis complex. Additional developments using SNPs will help stabilizing it.

Quick and cheap MIRU-VNTR typing of Mycobacterium tuberculosis species complex using duplex PCR

While minisatellites are usually typed using capillary sequencers or qiaplex systems in developed countries, many low-resource regions cannot afford it. We propose an optimized agarose gel electrophoresis method to genotype Mycobacterium tuberculosis species complex minisatellites in their standardized format (24 MIRU-VNTR). It is based on duplex PCRs combining VNTR loci harboring distinct amplicon sizes whatever the repetition number of each locus. This method performs well both on DNA extracts of good quality and on thermolysates while reducing workload and reagents costs.

Case study of primary imatinib resistance and correlation of BCR-ABL multiple mutations in chronic myeloid leukemia

Background: The kinase inhibitor, imatinib (Gleevec™, Novartis) has proven to be an effective treatment for chronic myeloid leukemia, providing proof-of-principle for a molecularly targeted approach in oncology. Despite its success in BCR-ABL-positive chronic myeloid leukemia patients, primary imatinib resistance has emerged, resulting in disease relapse. Little is known about the underlying genetic causes of resistance, however, with emerging pharmacogenomic approaches, a more comprehensive picture is developing. In imatinib-resistant patients, point mutations have been detected in an ATP-binding domain of the ABL gene, which disturbs the binding of imatinib to this target leading to resistance. However, it remains to be determined whether these mutations confer primary imatinib resistance. Methods: Primary imatinib resistance was observed in a chronic myeloid leukemia patient with no hematological, cytogenetic and molecular response to 9 months treatment with 400 mg imatinib/day. A highly sensitive allele-specific oligonucleotide polymerase chain reaction was established to detect point mutations in BCR-ABL adenosine triphosphate-binding domain. Results: C944T and T1052C mutations were detected which cause complete and partial imatinib resistance, respectively. Conclusions: This is a case study of multiple point mutations conferring primary imatinib resistance in one patient at the same time. Elucidating the biological mechanisms of primary imatinib resistance will improve the ability to predict patient responsiveness and provide effective clinical management. Furthermore, the allele-specific oligonucleotide-polymerase chain reaction assay is very effective in detecting mutations related to imatinib resistance.

Reverse line probe assay for cheap detection of Single Nucleotide Polymorphisms in Mycobacterium tuberculosis

More and more Single Nucleotide Polymosrphisms of interest among pathogenic organisms are described with the advent of Whole Genome Sequencing but WGS approach is still too expensive, time consuming, and relying on bioinformatical means that are not available in many developing countries. This study presents a low-cost reverse hybridization line probe technique for detecting SNPs in Mycobacterium tuberculosis. The proposed test is able to detect mutations in the RRDR of rpoB gene in M. tuberculosis with specificity and sensitivity of 98% and 100%, respectively and for an average cost of less than €3 per sample. The technique proved efficient not only on pure DNA samples extracted from culture isolates but also on crude extracts from clinical samples. The flexibility of the platform allows to get it transformed to any kind of test detection, hence, building a bridge between rich countries performing SNP discovery and countries with high burden that can target these SNPs on the collected samples.