Rashna S Dastur

Bio: Rashna S Dastur is an academic researcher from Bombay Hospital, Indore. The author has contributed to research in topics: Muscular dystrophy & Dysferlinopathy. The author has an hindex of 7, co-authored 12 publications receiving 176 citations.

Genetic landscape and novel disease mechanisms from a large LGMD cohort of 4656 patients.

Abstract: Author(s): Nallamilli, Babi Ramesh Reddy; Chakravorty, Samya; Kesari, Akanchha; Tanner, Alice; Ankala, Arunkanth; Schneider, Thomas; da Silva, Cristina; Beadling, Randall; Alexander, John J; Askree, Syed Hussain; Whitt, Zachary; Bean, Lora; Collins, Christin; Khadilkar, Satish; Gaitonde, Pradnya; Dastur, Rashna; Wicklund, Matthew; Mozaffar, Tahseen; Harms, Matthew; Rufibach, Laura; Mittal, Plavi; Hegde, Madhuri | Abstract: ObjectiveLimb-girdle muscular dystrophies (LGMDs), one of the most heterogeneous neuromuscular disorders (NMDs), involves predominantly proximal-muscle weakness with g30 genes associated with different subtypes. The clinical-genetic overlap among subtypes and with other NMDs complicate disease-subtype identification lengthening diagnostic process, increases overall costs hindering treatment/clinical-trial recruitment. Currently seven LGMD clinical trials are active but still no gene-therapy-related treatment is available. Till-date no nation-wide large-scale LGMD sequencing program was performed. Our objectives were to understand LGMD genetic basis, different subtypes' relative prevalence across US and investigate underlying disease mechanisms.MethodsA total of 4656 patients with clinically suspected-LGMD across US were recruited to conduct next-generation sequencing (NGS)-based gene-panel testing during June-2015 to June-2017 in CLIA-CAP-certified Emory-Genetics-Laboratory. Thirty-five LGMD-subtypes-associated or LGMD-like other NMD-associated genes were investigated. Main outcomes were diagnostic yield, gene-variant spectrum, and LGMD subtypes' prevalence in a large US LGMD-suspected population.ResultsMolecular diagnosis was established in 27% (1259 cases; 95% CI, 26-29%) of the patients with major contributing genes to LGMD phenotypes being: CAPN3(17%), DYSF(16%), FKRP(9%) and ANO5(7%). We observed an increased prevalence of genetically confirmed late-onset Pompe disease, DNAJB6-associated LGMD subtype1E and CAPN3-associated autosomal-dominant LGMDs. Interestingly, we identified a high prevalence of patients with pathogenic variants in more than one LGMD gene suggesting possible synergistic heterozygosity/digenic/multigenic contribution to disease presentation/progression that needs consideration as a part of diagnostic modality.InterpretationOverall, this study has improved our understanding of the relative prevalence of different LGMD subtypes, their respective genetic etiology, and the changing paradigm of their inheritance modes and novel mechanisms that will allow for improved timely treatment, management, and enrolment of molecularly diagnosed individuals in clinical trials.

Ancestral founder mutations in calpain-3 in the Indian Agarwal community: historical, clinical, and molecular perspective.

Abstract: Introduction Clinical heterogeneity of limb-girdle muscular dystrophies (LGMDs, 24 known subtypes), which includes overlapping phenotypes and varying ages of onset and morbidity, adds complexity to clinical and molecular diagnoses. Methods To diagnose LGMD subtype, protein analysis, using immunohistochemistry (IHC) and immunoblotting, was followed by gene sequencing through a panel approach (simultaneous sequencing of known LGMD genes) in 9 patients from unrelated families of the Indian Agarwal community. Haplotype studies were performed by targeted SNP genotyping to establish mutation segregation. Results We identified 2 founder mutations in CAPN3, a missense (c.2338G>C; p.D780H) and a splice-site (c.2099-1G>T) mutation, on 2 different haplotype backgrounds. The patients were either heterozygous for both or homozygous for either of these mutations. Conclusions Founder mutations have immediate clinical application, at least in selected population groups. Clinically available gene panels may provide a definitive molecular diagnosis for heterogeneous disorders such as LGMD. Muscle Nerve 47: 931–937, 2013

Clinical and Genomic Evaluation of 207 Genetic Myopathies in the Indian Subcontinent.

Abstract: Objective: Inherited myopathies comprise more than 200 different individually rare disease-subtypes, but when combined together they have a high prevalence of 1 in 6,000 individuals across the world. Our goal was to determine for the first time the clinical- and gene-variant spectrum of genetic myopathies in a substantial cohort study of the Indian subcontinent. Methods: In this cohort study, we performed the first large clinical exome sequencing (ES) study with phenotype correlation on 207 clinically well-characterized inherited myopathy-suspected patients from the Indian subcontinent with diverse ethnicities. Results: Clinical-correlation driven definitive molecular diagnosis was established in 49% (101 cases; 95% CI, 42-56%) of patients with the major contributing pathogenicity in either of three genes, GNE (28%; GNE-myopathy), DYSF (25%; Dysferlinopathy), and CAPN3 (19%; Calpainopathy). We identified 65 variant alleles comprising 37 unique variants in these three major genes. Seventy-eight percent of the DYSF patients were homozygous for the detected pathogenic variant, suggesting the need for carrier-testing for autosomal-recessive disorders like Dysferlinopathy that are common in India. We describe the observed clinical spectrum of myopathies including uncommon and rare subtypes in India: Sarcoglycanopathies (SGCA/B/D/G), Collagenopathy (COL6A1/2/3), Anoctaminopathy (ANO5), telethoninopathy (TCAP), Pompe-disease (GAA), Myoadenylate-deaminase-deficiency-myopathy (AMPD1), myotilinopathy (MYOT), laminopathy (LMNA), HSP40-proteinopathy (DNAJB6), Emery-Dreifuss-muscular-dystrophy (EMD), Filaminopathy (FLNC), TRIM32-proteinopathy (TRIM32), POMT1-proteinopathy (POMT1), and Merosin-deficiency-congenital-muscular-dystrophy-type-1 (LAMA2). Thirteen patients harbored pathogenic variants in >1 gene and had unusual clinical features suggesting a possible role of synergistic-heterozygosity/digenic-contribution to disease presentation and progression. Conclusions: Application of clinically correlated ES to myopathy diagnosis has improved our understanding of the clinical and genetic spectrum of different subtypes and their overlaps in Indian patients. This, in turn, will enhance the global gene-variant-disease databases by including data from developing countries/continents for more efficient clinically driven molecular diagnostics.

Becker muscular dystrophy in Indian patients: analysis of dystrophin gene deletion patterns.

Abstract: Background: Becker muscular dystrophy (BMD) is caused by mutations in the dystrophin gene with variable phenotypes. Becker muscular dystrophy patients have low levels of nearly full-length dystrophin and carry in-frame mutations, which allow partial functioning of the protein. Aim: To study the deletion patterns of BMD and to correlate the same with reading frame rule and different phenotypes. Setting: A tertiary care teaching hospital. Design: This is a prospective hospital-based study. Materials and Methods: Thirty-two exons spanning different hot spot regions using Multiplex PCR techniques were studied in 347 patients. Two hundred and twenty-two showed deletions in one or more of the 32 exons. Out of these, 46 diagnosed as BMD patients were analyzed. Results: Forty-six BMD patients showed deletions in both regions of the dystrophin gene. Out of these 89.1% (41/46) were in-frame deletions. Deletions starting with Exon 45 were found in 76.1% (35/46) of the cases. Mutations in the majority of cases i.e. 39/46 (84.8%) were seen in 3' downstream region (Exon 45-55, distal rod domain). Few, i.e. 5/46 (10.8%) showed deletions in 5' upstream region (Exons 3-20, N-terminus and proximal rod domain) of the gene, while in 2/46 (4.4%) large mutations (>40 bp) spanning both regions (Exons 3-55) were detected. Conclusion: This significant gene deletion analysis has been carried out for BMD patients particularly from Western India using 32 exons.

Correlation between deletion patterns of SMN and NAIP genes and the clinical features of spinal muscular atrophy in Indian patients.

Abstract: Background: Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder involving degeneration of anterior horn cells of spinal cord resulting in progressive muscle weakness and atrophy. Aims: The molecular analysis of two marker genes for spinal muscular atrophy (SMA) i.e., the survival motor neuron gene (SMN) and the neuronal apoptosis inhibitory protein gene (NAIP) was conducted in 39 Indian patients with clinical symptoms of SMA. Out of these, 28 showed homozygous deletions and the phenotypic features of these SMA patients were compared with the corresponding genotypes. Settings: A tertiary care teaching Hospital. Design: This is a prospective hospital based study. Materials and Methods: Polymerase chain reaction (PCR) combined with restriction fragment length polymorphism (RFLP) was used to detect the deletion of exon 7 and exon 8 of SMN1 gene, as well as multiplex PCR for exon 5 and 13 of NAIP gene. Results: Exons 7 and 8 of SMN and NAIP (exon 5) were homozygously deleted in 73% of SMA I and 27% of SMA II patients. SMN exon 7 and 8 deletions without NAIP deletions were seen in 27% of type I SMA and 46% of SMA type II patients. Two patients of type III SMA showed single deletion of SMN exon 7 along with 27% of SMA type II patients. Conclusion: With the advent of molecular biology techniques, SMN gene deletion studies have become the first line of investigation for confirmation of a clinical diagnosis of SMA. The findings of homozygous deletions of exons 7 and/or 8 of SMN1 gene confirms the diagnosis of SMA, even in patients with atypical clinical features. Deletions of NAIP gene were mainly seen in severely affected patients, hence is useful for predicting the prognosis.

Genetic landscape and novel disease mechanisms from a large LGMD cohort of 4656 patients.

Abstract: Author(s): Nallamilli, Babi Ramesh Reddy; Chakravorty, Samya; Kesari, Akanchha; Tanner, Alice; Ankala, Arunkanth; Schneider, Thomas; da Silva, Cristina; Beadling, Randall; Alexander, John J; Askree, Syed Hussain; Whitt, Zachary; Bean, Lora; Collins, Christin; Khadilkar, Satish; Gaitonde, Pradnya; Dastur, Rashna; Wicklund, Matthew; Mozaffar, Tahseen; Harms, Matthew; Rufibach, Laura; Mittal, Plavi; Hegde, Madhuri | Abstract: ObjectiveLimb-girdle muscular dystrophies (LGMDs), one of the most heterogeneous neuromuscular disorders (NMDs), involves predominantly proximal-muscle weakness with g30 genes associated with different subtypes. The clinical-genetic overlap among subtypes and with other NMDs complicate disease-subtype identification lengthening diagnostic process, increases overall costs hindering treatment/clinical-trial recruitment. Currently seven LGMD clinical trials are active but still no gene-therapy-related treatment is available. Till-date no nation-wide large-scale LGMD sequencing program was performed. Our objectives were to understand LGMD genetic basis, different subtypes' relative prevalence across US and investigate underlying disease mechanisms.MethodsA total of 4656 patients with clinically suspected-LGMD across US were recruited to conduct next-generation sequencing (NGS)-based gene-panel testing during June-2015 to June-2017 in CLIA-CAP-certified Emory-Genetics-Laboratory. Thirty-five LGMD-subtypes-associated or LGMD-like other NMD-associated genes were investigated. Main outcomes were diagnostic yield, gene-variant spectrum, and LGMD subtypes' prevalence in a large US LGMD-suspected population.ResultsMolecular diagnosis was established in 27% (1259 cases; 95% CI, 26-29%) of the patients with major contributing genes to LGMD phenotypes being: CAPN3(17%), DYSF(16%), FKRP(9%) and ANO5(7%). We observed an increased prevalence of genetically confirmed late-onset Pompe disease, DNAJB6-associated LGMD subtype1E and CAPN3-associated autosomal-dominant LGMDs. Interestingly, we identified a high prevalence of patients with pathogenic variants in more than one LGMD gene suggesting possible synergistic heterozygosity/digenic/multigenic contribution to disease presentation/progression that needs consideration as a part of diagnostic modality.InterpretationOverall, this study has improved our understanding of the relative prevalence of different LGMD subtypes, their respective genetic etiology, and the changing paradigm of their inheritance modes and novel mechanisms that will allow for improved timely treatment, management, and enrolment of molecularly diagnosed individuals in clinical trials.

Emery–Dreifuss Muscular Dystrophy

Abstract: Emery–Dreifuss muscular dystrophy (EDMD) is an early life muscular dystrophy characterised by early contractures, progressive muscular weakness and cardiac involvement. The transmission is usually X-linked but autosomal forms occur. The condition results from abnormalities of three groups of proteins together referred to as protein envelopathies. Therapy revolves around management of cardiac issues and maintenance of mobility and strategies for contractures.

Neuromuscular Diseases Due to Chaperone Mutations: A Review and Some New Results.

Abstract: Skeletal muscle and the nervous system depend on efficient protein quality control, and they express chaperones and cochaperones at high levels to maintain protein homeostasis. Mutations in many of these proteins cause neuromuscular diseases, myopathies, and hereditary motor and sensorimotor neuropathies. In this review, we cover mutations in DNAJB6, DNAJB2, αB-crystallin (CRYAB, HSPB5), HSPB1, HSPB3, HSPB8, and BAG3, and discuss the molecular mechanisms by which they cause neuromuscular disease. In addition, previously unpublished results are presented, showing downstream effects of BAG3 p.P209L on DNAJB6 turnover and localization.

Protein and genetic diagnosis of limb girdle muscular dystrophy type 2A: The yield and the pitfalls

Abstract: Limb girdle muscular dystrophy type 2A (LGMD2A) is the most frequent form of LGMD worldwide. Comprehensive clinical assessment and laboratory testing is essential for diagnosis of LGMD2A. Muscle immunoblot analysis of calpain-3 is the most useful tool to direct genetic testing, as detection of calpain-3 deficiency has high diagnostic value. However, calpain-3 immunoblot testing lacks sensitivity in about 30% of cases due to gene mutations that inactivate the enzyme. The best diagnostic strategy should be determined on a case-by-case basis, depending on which tissues are available, and which molecular and/or genetic methods are adopted. In this work we survey the current knowledge, advantages, limitations, and pitfalls of protein testing and mutation detection in LGMD2A and provide an update of genetic epidemiology.