Biology subjects

Majumdar, U.

Publications and source records attributed to Majumdar, U..

4 recordsLinked to original sources

bioRxiv2021

Inhibition of BKCa channels protects neonatal hearts against myocardial ischemia and reperfusion injury

BKCa channels are large-conductance calcium and voltage-activated potassium channels that are heterogeneously expressed in a wide array of cells. Activation of BKCa channels present in mitochondria of adult ventricular cardiomyocytes is implicated in cardioprotection against ischemia-reperfusion (IR) injury. However, the BKCa channels activity has never been detected in the plasma membrane of adult ventricular cardiomyocytes. In this study, we report the presence of the BKCa channel in the plasma membrane and mitochondria of neonatal murine and rodent cardiomyocytes which protects the heart on inhibition but not activation. Furthermore, K+ currents measured in neonatal cardiomyocyte (NCM) was sensitive to iberiotoxin (IbTx), suggesting the presence of BKCa channels in the plasma membrane. Neonatal hearts subjected to IR when post-conditioned with NS1619 during reoxygenation increased the myocardial infarction whereas IbTx reduced the infarct size. In agreement, isolated NCM also presented increased apoptosis on treatment with NS1619 during hypoxia and reoxygenation, whereas IbTx reduced TUNEL positive cells. In NCMs, activation of BKCa channels increased the intracellular reactive oxygen species post HR injury. Electrophysiological characterization of NCMs indicated that NS1619 increased the beat period, field, and action potential duration, and decreased the conduction velocity and spike amplitude. In contrast, IbTx had no impact on the electrophysiological properties of NCMs. Taken together, our data established that inhibition of plasma membrane BKCa channels in the NCM protects neonatal heart/cardiomyocytes from IR injury. Furthermore, the functional disparity observed towards the cardioprotective activity of BKCa channels in adults compared to neonatal heart could be attributed to their differential localization.

physiology↗

bioRxiv2021

Maternal hyperglycemia impedes second heart field-derived cardiomyocyte differentiation to elevate the risk of congenital heart defects

Congenital heart disease (CHD) is the most prevalent structural malformations of the heart affecting [~]1% of live births. To date, both damaging genetic variations and adverse environmental exposure such as maternal diabetes have been found to cause CHD. Clinical studies show [~]fivefold higher risk of CHD in the offspring of mothers with pregestational diabetes. Maternal pregestational diabetes affects the gene regulatory networks key to proper cardiac development in the fetus. However, the cell-type specificity of these gene regulatory responses to maternal diabetes and their association with the observed cardiac defects in the fetuses remains unknown. To uncover the transcriptional responses to maternal diabetes in the early embryonic heart, we used an established murine model of pregestational diabetes. In this model, we have previously demonstrated an increased incidence of CHD. Here, we show maternal hyperglycemia (matHG) elicits diverse cellular responses during heart development by single-cell RNA-sequencing in embryonic hearts exposed to control and matHG environment. Through differential gene-expression and pseudotime trajectory analyses of this data, we identified changes in lineage specifying transcription factors, predominantly affecting Isl1+ second heart field progenitors and Tnnt2+ cardiomyocytes with matHG. Using in vivo cell-lineage tracing studies, we confirmed that matHG exposure leads to impaired second heart field-derived cardiomyocyte differentiation. Finally, this work identifies matHG-mediated transcriptional determinants in cardiac cell lineages elevate CHD risk and show perturbations in Isl1-dependent gene-regulatory network (Isl1-GRN) affect cardiomyocyte differentiation. Functional analysis of this GRN in cardiac progenitor cells will provide further mechanistic insights into matHG-induced severity of CHD associated with diabetic pregnancies.

developmental biology↗

bioRxiv2020

Nitric oxide prevents aortic valve calcification by S-nitrosylation of USP9X to activate NOTCH signaling

Calcific aortic valve disease (CAVD) is an increasingly prevalent condition and endothelial dysfunction is implicated in its etiology. We previously identified nitric oxide (NO) as a calcification inhibitor by its activation of NOTCH1, which is genetically linked to human CAVD. Here, we show that NO rescues calcification by a S-nitrosylation-mediated mechanism in porcine aortic valve interstitial cells (pAVICs) and single cell RNA-seq demonstrated regulation of NOTCH pathway by NO. A unbiased proteomic approach to identify S-nitrosylated proteins in valve cells found enrichment of the ubiquitin proteasome pathway and implicated S-nitrosylation of USP9X in NOTCH regulation during calcification. Furthermore, S-nitrosylated USP9X was shown to deubiquitinate and stabilize MIB1 for NOTCH1 activation. Consistent with this, genetic deletion of Usp9x in mice demonstrated aortic valve disease and human calcified aortic valves displayed reduced S-nitrosylation of USP9X. These results demonstrate a novel mechanism by which S-nitrosylation dependent regulation of ubiquitin-associated pathway prevents CAVD.

cell biology↗

bioRxiv2018

A large-scale systemic RNAi screen in the red flour beetle Tribolium castaneum identifies novel genes involved in arthropod muscle development

Although muscle development has been widely studied in Drosophila melanogaster there are still many gaps in our knowledge, and it is not known to which extent this knowledge can be transferred to other insects. To help in closing these gaps we participated in a large-scale RNAi screen that used the red flour beetle, Tribolium castaneum, as a screening platform. The effects of systemic RNAi were screened upon double-stranded RNA injections into appropriate muscle-EGFP tester strains. Injections into pupae were followed by the analysis of the late embryonic/early larval muscle patterns, and injections into larvae by the analysis of the adult thoracic muscle patterns. Herein we describe the results of the first-pass screens with pupal and larval injections, which covered ~8,500 and ~5,000 genes, respectively, of a total of ~16,500 genes of the Tribolium genome. Apart from many genes known from Drosophila as regulators of muscle development, a collection of genes previously unconnected to muscle development yielded phenotypes in larval body wall and leg muscles as well as in indirect flight muscles. We then present the main candidates from the pupal injection screen that remained after being processed through a series of verification and selection steps. Further, we discuss why distinct though overlapping sets of genes are revealed by the Drosophila and Tribolium screening approaches.

developmental biology↗