One of the multitasking proteins, transactive response DNA-binding protein 43 (tdp43) plays a key role in RNA regulation and the two pathogenic mutations such as D169G and K263E, located at the RNA Recognition Motif (RRM) of tdp43, are reported to cause neurological disorders such as Amyotrophic Lateral Sclerosis and FrontoTemporal Lobar Degeneration. As the exploration of the proteinopathy demands both structural and functional characterizations of mutants, a comparative analysis on the wild type and mutant tdp43 (D169G and K263E) and their complexes with RNA has been performed using computational approaches. Molecular dynamics simulations revealed comparatively stable mutant structures compared to wild type tdp43. Both mutants show lesser binding affinity toward RNA molecule when compared to the wild type tdp43. Some of the observed features, including the increased solvent-accessible surface area, conformational flexibility as well as unfolding of tdp43, and the altered RNA conformation in tp43-RNA complex, reveal the susceptibility of these mutants to induce conformational changes in tdp43 for a possible aggregation in the cytoplasm. Particularly, the enhanced aggregation propensity of both mutants also evidences the higher probability of cytoplasmic aggregation of tdp43 mutants. Hence, the present analysis highlighting the structural and functional aspects of wild and mutant tdp43 will form the basis to gain insight into the proteinopathy of tdp43 and the related structure-based drug discovery. Thus, tdp43 can be used as target to develop novel therapeutic approaches or drug designing.

The human Argonaute2 protein (Ago2) is a key player in RNA interference pathway and small RNA recognition by Ago2 is the crucial step in siRNA mediated gene silencing mechanism. The present study highlights the structural and functional dynamics of human Ago2 and the interaction mechanism of Ago2 with a set of seven siRNAs for the first time. The human Ago2 protein adopts two conformations such as “open” and “close” during the simulation of 25 ns. One of the domains named as PAZ, which is responsible for anchoring the 3′-end of siRNA guide strand, is observed as a highly flexible region. The interaction between Ago2 and siRNA, analyzed using a set of siRNAs (targeting at positions 128, 251, 341, 383, 537, 1113, and 1115 of mRNA) designed to target tdp43 mutants causing Amyotrophic Lateral Sclerosis (ALS) disease, revealed the stable and strong recognition of siRNA by the Ago2 protein during dynamics. Among the studied siRNAs, the siRNA341 is identified as a potent siRNA to recognize Ago2 and hence could be used further as a possible siRNA candidate to target the mutant tdp43 protein for the treatment of ALS patients.

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Tau is a microtubule-associated protein whose C-terminal domain consisting of four repeat regions R1, R2, R3 and R4 binds to microtubules to stabilize them. In several neurodegenerative diseases, tau detaches from microtubules to form insoluble aggregates leading to tauopathy. Microtubules are made up of αβ tubulin subunits. Seven α-tubulin and nine β-tubulin isotypes have been reported to be present in humans till date. These tubulin isotypes show residue composition variations mainly at C-terminal region and bind to motor proteins and anti-mitotic drugs differently. These tubulin isotypes show tissue specific expression as their relative proportion varies significantly in different type of cells. It is also known that tau binds differently to different cell lines and can either promote or demote microtubule polymerization. However, the relative binding affinity of tau to the different β-tubulin isotypes present in different cell lines is completely unknown. Here, we study relative binding affinity of Tau repeat region R2 to neuronal specific tubulin isotypes βI, βIIb, and βIII using molecular modelling approach. The order of binding energy of tau with tubulin is βIII > βIIb > βI. Our strategy can be potentially adapted to understand differential binding affinity of tau towards β-tubulin isotypes present in other cell lines.

Background Vitamin D dependent rickets type 1 (VDDR1) is a rare disease due to pathogenic variants in 1-α hydroxylase gene. We describe our experience with systematic review of world literature to describe phenotype and genotype. Methods Seven patients from six unrelated families with genetically proven VDDR1 from our cohort and 165 probands from systematic review were analyzed retrospectively. The clinical features, biochemistry, genetics, management, and long-term outcome were retrieved. Results In our cohort, the median age at presentation and diagnosis was 11(4–18) and 40(30–240) months. The delayed diagnoses were due to misdiagnoses as renal tubular acidosis and hypophosphatemic rickets. Four had hypocalcemic seizures in infancy whereas all had rickets by 2 years. All patients had biochemical response to calcitriol, however two patients diagnosed post-puberty had persistent deformity. Genetic analysis revealed two novel (p.Met260Arg, p.Arg453Leu) and a recurring variant (p.Phe443Profs*24). Systematic review showed that seizures as most common presentation in infancy, whereas delayed motor milestones and deformities after infancy. Diagnosis was delayed in 27 patients. Patients with unsatisfactory response despite compliance were >12 years at treatment initiation. Inappropriately normal 1,25(OH)2D may be present, however suppressed ratio of 1,25(OH)2 D/25(OH)D may provide a clue to diagnosis. Various region specific and hot-spot recurrent variants are described. Patients with truncating variants had higher daily calcitriol requirement and greatly suppressed ratio of 1,25(OH)2D/25(OH)D. Conclusion Delayed diagnosis may lead to permanent short stature and deformities. Truncating variants tend to have severe disease as compared to non-truncating variants. Diagnostic accuracy of 1,25(OH)2 D/25(OH)D ratio needs further validation.