Biology subjects

Bakshi, S.

Publications and source records attributed to Bakshi, S..

23 records · Page 2Linked to original sources

bioRxiv2020

Transcriptomic analysis of naïve human embryonic stem cells cultured in three-dimensional PEG scaffolds

Derivation of primed and naive human embryonic stem cells (ESCs) have prompted an increased interest in devising culture conditions for maintaining their pluripotency and differential potential. Naive ESCs are characterized by improved viability, proliferation, and differentiation capacity in comparison to primed ESCs. However, traditional two-dimensional (2-D) cell culture techniques fail to mimic the three-dimensional (3-D) in vivo microenvironment, which results in altered morphological and molecular characteristics of ESCs. Here, we describe the use of 3-D self-assembling scaffolds that support growth and maintenance of the naive state characteristics of human ESC line, Elf1. Scaffolds were formed via a Michael addition reaction upon combination of two 8-arm polyethylene glycol (PEG) polymers functionalized with thiol (PEG-8-SH) and acrylate (PEG-8-Acr) end groups. 3-D scaffolds not only maintained the naive state, but also supported long-term growth for up to 3 weeks without requiring routine passaging and manipulation. 3-D grown cells exhibited upregulation of core (OCT4, NANOG, and SOX2) and naive (KLF17, KLF4, TFCP2L1, DPPA3, and DNMT3L) genes. These genes returned to normal levels when 3-D grown cells were propagated under 2-D culture conditions. Examination of RNA-sequencing demonstrated significant changes in gene expression profiles between 2-D and 3-D grown Elf1 cells. Gene Ontology analysis revealed upregulation of biological processes involved in the regulation of transcription and translation, as well as {beta}-catenin-TCF complex assembly, extracellular matrix organization, and chromatin remodeling in 3-D grown Elf1 cells. 3-D culture conditions also induced upregulation of genes associated with several signaling pathways including Wnt signaling and focal adhesion. However, p53 signaling pathway associated genes were downregulated under these culture conditions. Our findings provide insight into the possible mechanisms of prolonged self-renewal as well as upregulation of pluripotent genes stimulated by the transduction of mechanical signals from the 3-D microenvironment.

cell 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↗

bioRxiv2020

Dynamic Regulation of Growth and Physiology of Microbes under Complex Changing Conditions

As bacteria transition from exponential to stationary phase they change greatly in size, morphology, growth and expression-profiles. These responses also vary between individual cells, but it has proven difficult to track cell lineages along the growth curve to determine the progression of events or correlations between how individual cells enter and exit dormancy. We developed a platform for tracking >105 parallel cell lineages in dense and changing cultures, independently validating that the imaged cells closely track batch populations. Initial applications show that for both Escherichia coli and Bacillus subtilis, growth changes from an adder mode in exponential phase to mixed adders-timers entering stationary phase, and then a near-perfect sizer upon exit - creating broadly distributed cell sizes in stationary phase but rapidly returning to narrowly distributed sizes upon exit. Furthermore, cells that undergo more divisions entering stationary phase suffer reduced survival after long periods of dormancy but are the only cells observed that persist against antibiotics.

microbiology↗

bioRxiv2018

Variability of bacterial behavior in the mammalian gut captured using a growth-linked single-cell synthetic gene oscillator

The dynamics of the bacterial population that comprises the gut microbiota plays key roles in overall mammalian health. However, a detailed understanding of bacterial growth within the gut is limited by the inherent complexity and inaccessibility of the gut environment. Here, we deploy an improved synthetic genetic oscillator to investigate dynamics of bacterial colonization and growth in the mammalian gut under both healthy and disease conditions. The synthetic oscillator, when introduced into both Escherichia coli and Salmonella Typhimurium maintains regular oscillations with a constant period in generations across growth conditions. We determine the phase of oscillation from individual bacteria using image analysis of resultant colonies and thereby infer the number of cell divisions elapsed. In doing so, we demonstrate robust functionality and controllability of the oscillator circuits activity during bacterial growth in vitro, in a simulated murine gut microfluidic environment, and in vivo within the mouse gut. We determine different dynamics of bacterial colonization and growth in the gut under normal and inflammatory conditions. Our results show that a precise genetic oscillator can function in a complex environment and reveal single cell behavior under diverse conditions where disease may create otherwise impossible-to-quantify variability in growth across the population.

synthetic biology↗

bioRxiv2018

Genetic determinants of risk and survival in pulmonary arterial hypertension

BackgroundPulmonary arterial hypertension (PAH) is a rare disorder leading to premature death. Rare genetic variants contribute to disease etiology but the contribution of common genetic variation to disease risk and outcome remains poorly characterized.\n\nMethodsWe performed two separate genome-wide association studies of PAH using data across 11,744 European-ancestry individuals (including 2,085 patients), one with genotypes from 5,895 whole genome sequences and another with genotyping array data from 5,849 further samples. Cross-validation of loci reaching genome-wide significance was sought by meta-analysis. We functionally annotated associated variants and tested associations with duration of survival.\n\nFindingsA locus at HLA-DPA1/DPB1 within the class II major histocompatibility (MHC) region and a second near SOX17 were significantly associated with PAH. The SOX17 locus contained two independent signals associated with PAH. Functional and epigenomic data indicate that the risk variants near SOX17 alter gene regulation via an enhancer active in endothelial cells. PAH risk variants determined haplotype-specific enhancer activity and CRISPR-inhibition of the enhancer reduced SOX17 expression. Analysis of median survival showed that PAH patients with two copies of the HLA-DPA1/DPB1 risk variant had a two-fold difference (>16 years versus 8 years), compared to patients homozygous for the alternative allele.\n\nInterpretationWe have found that common genetic variation at loci in HLA-DPA1/DPB1 and an enhancer near SOX17 are associated with PAH. Impairment of Sox17 function may be more common in PAH than suggested by rare mutations in SOX17. Allelic variation at HLA-DPB1 stratifies PAH patients for survival following diagnosis, with implications for future therapeutic trial design.\n\nFundingUK NIHR, BHF, UK MRC, Dinosaur Trust, NIH/NHLBI, ERS, EMBO, Wellcome Trust, EU, AHA, ACClinPharm, Netherlands CVRI, Dutch Heart Foundation, Dutch Federation of UMC, Netherlands OHRD and RNAS, German DFG, German BMBF, APH Paris, Inserm, Universite Paris-Sud, and French ANR.

genetics↗