Biology subjects

Joshi, H.

Publications and source records attributed to Joshi, H..

26 records · Page 2Linked to original sources

bioRxiv2023

Estimation of Interaction and Growth Parameters to Develop a Computational Model for Gut Bacteria

The relevance of gut bacterial balance to human health can not be overemphasized. The gut bacterial balance delicately relies on several factors inherent to the person as well as to the environment. As the volume of evidences for the gut bacterial influence on health and the clinical data on the variance of the bacterial population across cohorts continue to grow exponentially, it is important to develop a theoretical model for gut bacteria. In this work, we suggest a new computational method for estimating the interaction parameters from the cross-sectional data of bacterial abundances in a cohort, without requiring a longitudinal followup. We introduce a nutrient type based bacterial growth model and use the Monte Carlo approach to estimate the matrix of interaction parameters for the 14 major bacterial species. These parameters were used in a comprehensive first-level computational model we developed for the large intestine to understand the patterns of re-establishing balance with different nutrient types.

biophysics↗

bioRxiv2022

Lossless end-to-end transport of small molecules through micron-length DNA nanochannels

Designed and engineered protein and DNA nanopores can sense and characterize single molecules and control transmembrane transport of molecular species. However, designed biomolecular pores are less than 100 nm in length and are used primarily for transport across lipid membranes. Nanochannels that span longer distances could be used as conduits for molecules between non-adjacent compartments or cells. Here, we design microns-long, 7 nm diameter DNA nanochannels that small molecules can traverse according to the laws of continuum diffusion. Binding DNA origami caps to channel ends eliminates transport and demonstrates that molecules diffuse from one channel end to the other rather than permeating through channel walls. These micron-length nanochannels can also grow, form interconnects, and interface with living cells. This work thus shows how to construct multifunctional, dynamic agents that control molecular transport, opening new ways of studying intercellular signaling and modulating molecular transport between synthetic and living cells. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=130 SRC="FIGDIR/small/488239v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@fec963org.highwire.dtl.DTLVardef@157bb83org.highwire.dtl.DTLVardef@d7a274org.highwire.dtl.DTLVardef@ea961c_HPS_FORMAT_FIGEXP M_FIG C_FIG

synthetic biology↗

bioRxiv2021

DNA Origami Voltage Sensors for Transmembrane Potentials with Single-Molecule Sensitivity

Signal transmission in neurons goes along with changes in the transmembrane potential. To report them, different approaches including optical voltage-sensing dyes and genetically encoded voltage indicators have evolved. Here, we present a DNA nanotechnology-based system. Using DNA origami, we incorporate and optimize different properties such as membrane targeting and voltage sensing modularly. As a sensing unit, we use a hydrophobic red dye anchored to the membrane and an anionic green dye at the DNA connecting the DNA origami and the membrane dye anchor. Voltage-induced displacement of the anionic donor unit is read out by changes of Fluorescence Resonance Energy Transfer (FRET) of single sensors attached to liposomes. They show a FRET change of [~]5% for {Delta}{Psi}=100 mV and allow adapting the potential range of highest sensitivity. Further, the working mechanism is rationalized by molecular dynamics simulations. Our approach holds potential for the application as non-genetically encoded sensors at membranes.

biophysics↗

bioRxiv2021

Empirical prediction of variant-associated cryptic-donors with 87% sensitivity and 95% specificity

Predicting which cryptic-donors may be activated by a genetic variant is notoriously difficult. Through analysis of 5,145 cryptic-donors activated by 4,811 variants (versus 86,963 decoy-donors not used; any GT or GC), we define an empirical method predicting cryptic-donor activation with 87% sensitivity and 95% specificity. Strength (according to four algorithms) and proximity to the authentic-donor appear important determinants of cryptic-donor activation. However, other factors such as auxiliary splicing elements, which are difficult to identify, play an important role and are likely responsible for current prediction inaccuracies. We find that the most frequent mis-splicing events at each exon-intron junction, mined from 40,233 RNA-sequencing samples, predict with remarkable accuracy which cryptic-donor will be activated in rare disease. Aggregate RNA-Sequencing splice-junction data provides an accurate, evidence-based method to predict variant-activated cryptic-donors in genetic disorders, assisting pathology consideration of possible consequences of a variant for the encoded protein and RNA diagnostic testing strategies.

genetics↗

bioRxiv2021

Membrane activity of a DNA-based ion channel depends on the stability of its double-stranded structure.

Structural DNA nanotechnology has emerged as a promising method for designing spontaneously-inserting and fully-controllable synthetic ion channels. However, both insertion efficiency and stability of existing DNA-based ion channels leave much room for improvement. Here, we demonstrate an approach to overcoming the unfavorable DNA-lipid interactions that hinder the formation of a stable transmembrane pore. Our all-atom MD simulations and experiments show that the insertion-driving cholesterol modifications, when introduced at an end of a DNA strand, are likely to cause fraying of the terminal base pairs as the DNA nanostructure adopts its energy-minimum configuration in the membrane. We also find that fraying of base pairs distorts nicked DNA constructs when embedded in a lipid bilayer. Here, we show that DNA nanostructures that do not have discontinuities (nicks) in their DNA backbones form considerably more stable DNA-induced conductive pores and insert into lipid membranes with a higher efficiency than the equivalent nicked constructs. Moreover, lack of nicks allows to design and maintain membrane-spanning helices in a tilted orientation within lipid bilayer. Thus, reducing the conformational degrees of freedom of the DNA nanostructures enables better control over their function as synthetic ion channels.

synthetic biology↗

bioRxiv2020

Proteomic profiling of peripheral blood mononuclear cells isolated from patients with tuberculosis and diabetes copathogenesis -A pilot study

BackgroundDiabetes is an important risk factor for developing tuberculosis. This association leads to exacerbation of tuberculosis symptoms and delayed treatment of both the diseases. Molecular mechanism and biomarkers/drug targets related to copathogenesis of tuberculosis and diabetes, however, still remains to be poorly understood. In this study, proteomics based 2D-MALDI/MS approach was employed to identify host signature proteins which are altered during copathogenesis of tuberculosis and diabetes. MethodsComparative proteome of human peripheral blood mononuclear cells (PBMCs) from healthy controls, tuberculosis and diabetes patients in comparison to comorbid diabetes and tuberculosis patients was analyzed. Gel based proteomics approach followed by in gel trypsin digestion and peptide identification by mass spectrometry was used for signature protein identification. ResultsTotal of 18 protein spots with differential expression in TBDM patients in comparison to other groups were identified. These include Vimentin, tubulin beta chain protein, superoxide dismutase, Actin related protein 2/3 complex subunit 2, PDZ LIM domain protein, Rho-GDP dissociation inhibitor, Ras related protein Rab, dCTPpyrophosphatase 1, Transcription initiation factor TFIID subunit 12, coffilin 1, three isoforms of Peptidylprolylcis-trans isomerase A, three isoforms of Protein S100A9, Protein S100A8 and SH3 domain containing protein. These proteins belonged to four functional categories i.e. structural, cell cycle/growth regulation, signaling and intermediary metabolism. ConclusionProteins identified to be differentially expressed in TBDM patient can act as potent biomarkers and as predictors for copathogenesis of tuberculosis and diabetes.

molecular biology↗

bioRxiv2019

Prevalence and risk factors of postpartum depression among women living in urban slums of Dhaka, Bangladesh

Postpartum depression (PPD) is a serious pubic health concern and known to have the adverse effects on mothers perinatal wellbeing; and childs physical and codnitive development. There were limited literatures on PPD in Bangladesh, especially in urban slum context. The aim of this study was to assess the burden and risk factors of PPD among the urban slum women. A cross-sectional study was conducted between November-December 2017 in three urban slums on 376 women within first 12 months of postpartum. A validated Bangla version of Edinburgh Postnatal Depression Scale was used to measure the depression status. Respondents socio-economic characteristics and other risk factors were collected with structured validated questionaire by trained interviewers. Unadjusted Prevalence Ratio (PR) and Adjusted Prevalence Ratio (APR) were estimated with Generalized Linear Model(GLM) and Generalized Estimating Equation (GEE) respectively to identify the risk factors of PPD. The prevalence of PPD was 39.4% within first 12 months following the child birth. Job involvement after child delivery (APR=1.9, 95% CI= 1.1, 3.3), job loss due to pregnancy (APR=1.5, 95% CI= 1.0, 2.1), perinatal and postnatal death (APR=1.4, 95% CI= 0.97, 2.0), unintended pregnancy (APR=1.8, 95% CI= 1.3, 2.5), management of delivery cost by borrowing, selling or mortgaging assets (APR=1.3, 95% CI= 0.94, 1.9), depressive symptom during pregnancy (APR=2.5, 95% CI= 1.7, 3.8) and intimate partner violence (APR=2.0, 95% CI= 1.2, 3.3), were identified as risk factors. PPD was not associated with poverty, mother in law and any child related factors. The burden of postpartum depression is high in the urban slum of Bangladesh. Maternal mental health services should be integrated with existing maternal health services. Research is required for the innovation of effective, low cost and culturally appropriate PPD case management and preventive intervention in urban slum of Bangladesh.

epidemiology↗

bioRxiv2017

Genetic polymorphism of Cytochrome-P450-2C9 (CYP2C9) in Indian populations

Cytochrome-P450-2C9 (CYP2C9) metabolizes wide range of drugs and highly express in human liver. Various mutations of CYP2C9 (R144C, I359L etc.), associated with drug-response, are highly diverse. We aimed to investigate the genetic diversity of CYP2C9 in Indian-subcontinent, using 1278 subjects from 36 populations. High frequency of CYP2C9*3 (0-0.179) was observed, comparative to other populations, including Europeans. Subjects having CYP2C9*3/*3 requires lower dose of warfarin, comparative to CYP2C9*1/*3 or CYP2C9*1/*1. Since, Indians are practicing marriage among their caste system, we predicted and observed high frequency (0-0.05) of CYP2C9*3/*3. Out of 21 populations, living outside of Indian subcontinent, only Toscani and Southern Han-Chinese have 0.009 and 0.01 CYP2C9*3/*3, respectively, lower than Indians. We found a non-synonymous mutation (L362V), observed only in Indian-subcontinent, and have 0-0.056 allelic, 0-0.037 L/V and 00.037 V/V genotype frequency. We observed unfavorable interatomic interactions between hydroxylation sites of warfarin and reactive oxyferryl heme in mutant, comparative to wild-type CYP2C9, in molecular dynamic simulations; and predict lower kinetic activity.

evolutionary biology↗