Research Projects

Inborn errors of metabolism (IEM) are rare heterogenous group of inherited disorders which result from disruption of activity in the metabolic pathway leading to either deficiency or accumulation of a specific metabolite. Though IEMs are individually rare, they are collectively common with a reported prevalence of 1:2497 live births in India. IEMs left undiagnosed and untreated leads to significant morbidity, mortality and contributes to 0.4% of deaths globally. As majority have treatment potential it is important for the clinicians to recognize and diagnose IEMs early. Till date, around 1450 IEMs have been described by ICIMD advisory group with 116 treatable neurometabolic disorders (139 genes) being discovered in the last decade. Molecular diagnosis becomes crucial for family planning, prenatal diagnostic testing, carrier testing, to monitor the disease prognosis and offer appropriate treatment options. The challenges encountered are even after extensive molecular investigations with whole exome sequencing and whole genome sequencing, still around 40 to 50% of children with neurometabolic disorders remain undiagnosed. The reason being, in spite of the rationally assembled ACMG/AMP guidelines to interpret variants, the molecular consequences are less well predicted for many variants or they are conflicting. Association of such variants to disease causation becomes difficult without support from further functional studies which is often difficult to perform on a routine basis. Even in a well curated database such as ClinVar over 50% of the variants have been placed under the category of Variants of uncertain significance (VUS). Of the VUS reported in ClinVar, majority are missense changes and many are intronic or in the regulatory regions with a small percentage of loss of function variants. Many of these variants are predicted to cause aberrant RNA transcript events (RNA phenotypes) such as aberrant expression, aberrant splicing or allelic imbalance. RNA-sequencing (RNA-seq) has evolved as a time-tested technique to solve one-third of cases in rare mendelian disorders. There exists a lack of understanding regarding the role of RNA-seq in exome negative neurometabolic disorders in children. To address this knowledge gap, the present study is being proposed to gain insights into the role of RNA-seq in the diagnostic yield of exome negative undiagnosed pediatric patients with neurometabolic disorders. Further, the gene transcripts obtained shall be correlated with the clinical phenotypes. We also attempt to study the pathological mechanism of mitochondrial abnormalities in subset of patients with mitochondrial disorders by analysis of mitochondrial bioenergetics, morphology, dynamics, electron transport complex protein expression and its calcium dynamics. This study will provide important and novel insights into the diagnostic utility of RNA seq and disease mechanisms in subset of patients with mitochondrial disorders.