Biology subjects

Vasudevan, M.

Publications and source records attributed to Vasudevan, M..

4 recordsLinked to original sources

bioRxiv2022

Differential structural organization and gene expression regulatory networks of lamin A Ig fold domain mutants of muscular dystrophy.

In metazoan cells, lamins form a proteinaceous meshwork as a major structural component of the nucleus and also play a role in regulating essential cellular processes. Lamins, along with their interactors, act as determinants for chromatin organization throughout the nucleus. The major dominant missense mutations responsible for autosomal dominant forms of muscular dystrophies reside in the Ig fold domain of lamin A. However, how lamin A contributes to the distribution of heterochromatin and balances euchromatin, and how it relocates epigenetic marks to shape chromatin states, remains poorly defined, making it difficult to draw conclusions about the prognosis of lamin A-mediated muscular dystrophies.In the first part of this report, we identified the in-vitro organization of full-length lamin A proteins due to two well-documented Ig LMNA mutations, R453W and W514R, through biophysical and electron microscopy observations. We further demonstrated that both lamin A/C mutant cells predominantly expressed nucleoplasmic aggregates with reduced amounts at the nuclear envelope. Labeling specific markers of epigenetics, such as H3K9me3, H3K27me3, H3K36me3, and HP1, allowed correlation of lamin A mutations with epigenetic mechanisms. Immunofluorescence and biochemical analyses indicated transcriptional upregulation. In addition to manipulating epigenetic mechanisms, our proteomic studies traced diverse expressions of transcription regulators, RNA synthesis and processing proteins, protein translation components, and posttranslational modifications. These data suggest severe perturbations in targeting other proteins to the nucleus.Our study also predicts specific structural configurations of lamin A determined by its interacting partners patterns. SignificanceO_LIThis study investigates the effects of two severe mutations in the LMNA gene associated with muscular dystrophies: R453W and W514R. C_LIO_LIThis research aims to provide new insights into the structural environment of full-length lamin A protein due to single-point mutations. C_LIO_LIOur study employs proteomics to map expression levels of regulators involved in epigenetic states, RNA synthesis and processing, and protein synthesis and processing. C_LIO_LIIt assesses potential effects on binding affinity and transcription, as well as alterations in heterochromatin protein distribution and RNA polymerase II functionality due to mutations affecting lamin A. C_LIO_LIA systematic investigation of lamin A interactors is conducted to explore their associations with other proteins. C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=67 SRC="FIGDIR/small/493956v2_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@10ac33dorg.highwire.dtl.DTLVardef@197fa20org.highwire.dtl.DTLVardef@a679daorg.highwire.dtl.DTLVardef@18a03a7_HPS_FORMAT_FIGEXP M_FIG Figure: Schematic diagram representing the results. Mutations in lamin A protein evicts the nucleosome from nuclear periphery and consequently promotes aberrant gene expression. C_FIG

biochemistry↗

bioRxiv2022

Interconnection between molecular regulators in LMNA related muscular dystrophy

Nuclear lamina is composed of different A-type and B-type lamin proteins and acts as major regulator of DNA replication, transcription, heterochromatin-euchromatin machinery. The majority of mutations in A type lamin are associated with some forms of muscular dystrophies,that majorly distinguishable by a common clinical feature : progressive skeletal muscle wasting. This speculates impaired skeletal muscle differentiation during development and after injury with the influence of myriad of signalling pathways. The molecular mechanism behind phenotypes of lamin A associated muscular dystrophies are still elusive . Here, we used genome wide expression analysis platform during the differentiation of murine C2C12 skeletal muscle cells to investigate the factors have been attributed to the disease. We compared the expression levels of the components of pathways that indicates important role of skeletal muscle as well as identified gene regulatory networks at two different time points of muscle differentiation in wild type and mutant cells. We also report significant perturbations in the expression and activation of Wnt signalling pathway in mutant cells among 40 dysregulated signalling pathways , presenting pronounced regulation of normal downstream myogenic signalling . Finally, with this largest data sets we evaluate in depth characterization of molecular effectors for myogenic differentiation, which could allow greater insight into development of therapeutic strategies for the remission of patients with LMNA linked muscle - related pathologies.

cell biology↗

bioRxiv2022

Evaluation of lamin A/C mechanotransduction under different surface topography in LMNA related muscular dystrophy.

Most of the single point mutations of the LMNA gene are associated with distinct muscular dystrophies, marked by heterogenous phenotypes but primarily the loss and symmetric weakness of skeletal muscle tissue. The molecular mechanism and phenotype-genotype relationships in these muscular dystrophies are poorly understood. An effort has been here to delineating the adaptation of mechanical inputs into biological response by mutant cells of lamin A associated muscular dystrophy. In this study we implement engineered smooth and pattern surfaces of particular young modulus to mimic muscle physiological range. Using fluorescence and atomic force microscopy we present distinct architecture of the actin filament along with abnormally distorted cell and nuclear shape in mutants, which showed a tendency to deviate from wild type cells. Topographic features of pattern surface antagonizes the binding of the cell with it. Correspondingly, from the analysis of genome wide expression data in wild type and mutant cells, we report differential expression of the gene products of the structural components of cell adhesion as well as LINC (linkers of nucleoskeleton and cytoskeleton) protein complexes. This study also reveals mis expressed downstream signaling processes in mutant cells, which could potentially lead to onset of the disease upon the application of engineered materials to substitute the role of conventional cues in instilling cellular behaviors in muscular dystrophies. Collectively, these data support the notion that lamin A is essential for proper cellular mechanotransduction from extracellular environment to the genome and impairment of the muscle cell differentiation in the pathogenic mechanism for lamin A associated muscular dystrophy.

cell biology↗

bioRxiv2021

EP300 (p300) mediated histone butyrylation is critical for adipogenesis

ObjectiveThe master epigenetic enzyme EP300 (p300) besides having lysine acetyltransferase activity can also catalyse other acylation modifications (propionylation, butyrylation, crotonylation etc.), the physiological implications of which are yet to be established fully. We hypothesized that p300 catalysed histone butyrylation may have a causal relationship with adipogenesis and the consequent obesity. MethodsHistone butyrylation pattern was investigated in 3T3L1 cells upon adipogenesis by immunoblotting and chromatin immunoprecipitation experiments. A small molecule modulator that could specifically inhibit p300 catalysed butyrylation without affecting its canonical acetyltransferase activity was screened from a series of compounds and then administered in differentiating 3T3L1 adipocytes as well as high fat diet-induced and genetically obese mice to validate the importance of butyrylation in adipogenesis. ResultsHistone butyrylation was increased upon adipogenesis both globally and locally in the promoters of pro-adipogenic genes along with an upregulation in the expression of acyl CoA generating enzyme Acss2, knockdown of which led to reduced butyrylation. Treatment of differentiating 3T3L1 cells with the p300 specific butyrylation inhibitor LTK-14A led to abrogation of adipogenesis with reduced expression of pro-adipogenic genes and inhibition of H4K5 butyrylation. LTK-14A administration could also attenuate weight gain in both mice models of obesity by preventing adipocyte hypertrophy via H4K5 butyrylation inhibition. ConclusionOur results indicate that p300 catalysed histone butyrylation may have a causal relationship with the process of adipogenesis. Site specific inhibition of butyrylation could lead to adipogenesis repression and hence this epigenetic modification could be targeted for obesity treatment. HighlightsO_LIHistone butyrylation has been established as a new epigenetic signature in the context of adipogenesis. C_LIO_LITo the best of our knowledge, this is the first report of a selective inhibitor of p300 catalysed histone acylation (butyrylation) without affecting its canonical acetyltransferase activity. C_LIO_LISpecific inhibition of H4K5 butyrylation could be a possible mechanism for inhibiting adipogenesis and hepatic steatosis leading to better control of obesity. C_LIO_LILTK-14A class of molecule could be developed as anti-obesity therapeutics. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=195 HEIGHT=200 SRC="FIGDIR/small/454641v3_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@1f29b35org.highwire.dtl.DTLVardef@abc5fcorg.highwire.dtl.DTLVardef@1534388org.highwire.dtl.DTLVardef@176d706_HPS_FORMAT_FIGEXP M_FIG Proposed model for the role of p300-mediated histone butyrylation in adipogenesis: In pre-adipocytes, there exists a basal level of histone acetylation while butyrylation is present to a much lesser extent owing to low stoichiometric levels of butyryl CoA. Induction of adipogenesis causes a simultaneous upregulation of histone acetylation and butyrylation marks leading to increased rate of adipogenesis and concomitant transcriptional activation of pro-adipogeneic genes. Onset of obesity in mice, either due to excess energy intake through high fat diet consumption or increased de novo synthesis of fatty acids due to leptin receptor gene mutation leading to hyperphagic behavior, is accompanied by adipocyte hyperplasia and hypertrophy. Both the organs of adipose tissue and liver were found to have enhanced levels of H4K5 butyrylation during obesity. LTK-14A, a butyrylation specific inhibitor could efficiently prevent the processes of adipogenesis and adipocyte hypertrophy due to inhibition of H4K5 butyrylation in these organs. Thus the compound could attenuate weight gain by selective inhibition of butyrylation without affecting acetylation, thereby highlighting the importance of histone butyrylation in adipogenesis and obesity. C_FIG

molecular biology↗