Biology subjects

Jagannathan, R.

Publications and source records attributed to Jagannathan, R..

4 recordsLinked to original sources

bioRxiv2025

TEAD1 is a novel regulator of NRF2 and oxidative stress response in cardiomyocytes

BACKGROUNDTEAD1, the mammalian Hippo pathway-regulated transcription factor, plays a critical and non-redundant role in maintaining cardiomyocyte (CM) homeostasis. However, the specific cellular pathways regulated by TEAD1 in CMs remain poorly defined. We hypothesized that TEAD1 has an essential, cell-autonomous role in the CM oxidative stress response by directly regulating the transcription of NRF2, the master regulator of oxidative stress response. METHODS AND RESULTSTamoxifen-induced conditional CM-specific TEAD1 deletion in adult mice leads to acute heart failure (HF) and altered expression of antioxidant genes. In silico analysis of publicly available RNA-seq data from human hearts with end-stage dilated (DCM) and ischemic (ICM) cardiomyopathy revealed significant downregulation of TEAD1 transcript levels and a positive correlation between TEAD1 and NRF2 gene expression. ChIP-seq and ATAC-seq in adult mouse hearts confirmed TEAD1 occupancy at promoter/enhancer elements within open chromatin regions of multiple antioxidant genes, including NRF2 and its targets. Ex vivo and in vitro TEAD1 knockout in primary neonatal and adult murine CMs, as well as in H9C2 cells, resulted in significantly increased cellular and mitochondrial ROS le, accompanied by a marked decrease in NRF2 expression and promoter-luciferase activity, under both basal and oxidative stress conditions. Mosaic, conditional deletion of TEAD1 in [~]40-50% of murine heart CMs provided a novel in vivo model for studying TEAD1-regulated pathways in the heart, independent of the confounding effects of HF. This model demonstrated reduced NRF2 expression and heightened oxidative stress in neonatal and adult TEAD1 mosaic knockout hearts. Notably, 8OHdG staining identified oxidative DNA damage in TEAD1-deficient CMs compared to TEAD1-expressing CMs within the mosaic knockout hearts. Upon in vivo AngII infusion, TEAD1 mosaic knockout hearts showed a significant increase in oxidative stress markers and an impaired NRF2 response. Overexpression of human TEAD1 restored NRF2 activity and mitigated ROS accumulation in TEAD1 knockout CMs in vitro. Furthermore, TEAD1 deletion in human iPSC-derived CMs resulted in increased oxidative stress and downregulation of NRF2 expression and functional activity, confirming the requirement of TEAD1 in NRF2-mediated oxidative stress response in human CMs. Collectively, these findings establish that TEAD1 is essential for NRF2 expression and activity under both basal and AngII-induced conditions and plays a crucial role in the oxidative stress response in CMs. CONCLUSIONSTEAD1 is a cell-autonomous, direct transcriptional regulator of NRF2 and the cardiomyocyte (CM) oxidative stress response. Its gene expression, which directly correlates with NRF2 transcript levels in the human myocardium, is significantly downregulated in human end-stage heart failure, potentially compromising the oxidative stress response in the failing heart.

molecular biology↗

bioRxiv2024

Hypomorphic NOTCH1 Expression Alters Cardiomyocyte Cellular Architecture in Hypoplastic Left Heart Syndrome

NOTCH1 is a protein involved in cardiac development and mutations in NOTCH1 are implicated in left sided congenital heart disease, including hypoplastic left heart syndrome (HLHS). Therapeutic advances for HLHS patients have been hampered by the absence of suitable experimental models. Here, using human induced pluripotent stem cells (hiPSCs), we have generated a series of CRISPR-edited complex heterozygous hypomorphic mutations in NOTCH1 that recapitulate mutations seen in HLHS patients. These cells demonstrate the downregulation of genes associated with mitochondria, the actin cytoskeleton, and cardiomyocyte development. In addition, these hypomorphic NOTCH1 hiPSCs cells showed an increased propensity to differentiate towards non-cardiomyocyte lineages such as fibroblasts and smooth muscle cells, a finding confirmed in HLHS patient-derived myocardial tissue. Abnormalities in sarcomeric and mitochondrial architecture contributed to decreased ATP production, abnormal calcium transients, and reduced contractility. Using a split nano-luciferase system as a NOTCH1 intracellular reporter, we screened a library of FDA-approved compounds. Auranofin, an agent currently employed for rheumatoid arthritis, was identified as a candidate drug that could rescue impaired differentiation and contractility seen in the hypomorphic NOTCH1 model. These findings point to cell-autonomous abnormalities in hypomorphic NOTCH1 pre-cardiomyocyte cells that can be leveraged to identify potential therapeutic strategies for patients with severe congenital cardiac abnormalities. HighlightsO_LICRISPR edited and patient-derived iPSCs with hypomorphic NOTCH1 expression were used to characterize a cell-based model of hypoplastic left heart syndrome. C_LIO_LIHypomorphic NOTCH1 iPSCs have abnormalities in pathways associated with mitochondrial function, actin cytoskeleton, and cardiomyocyte development. C_LIO_LIHypomorphic NOTCH1 iPSCs have less pluripotency and tend to skew differentiation away from cardiomyocytes and towards fibroblasts and smooth muscle cells. C_LIO_LINOTCH1 is required for cardiac cytoskeletal and mitochondrial architecture, and to preserve contractility and ATP production. C_LIO_LIA high-throughput drug screen identified auranofin as an agent that may benefit patients with hypoplastic left heart syndrome. C_LI

cell biology↗

bioRxiv2020

Bromodomain protein inhibition protects β-cells from cytokine-induced death and dysfunction via antagonism of NF-κB pathway.

Cytokine induced {beta}-cell apoptosis is the major pathogenic mechanism in type 1 diabetes (T1D). Despite significant advances in understanding underlying mechanisms, few drugs have been translated to protect {beta}-cells in T1D. Epigenetic modulators such as bromodomain-containing BET (Bromo- and Extra-Terminal) proteins are important regulators of immune responses. Pre-clinical studies have demonstrated a protective effect of BET inhibitors in NOD (non-obese diabetes) mouse model of T1D. However, the role of BET proteins in {beta}-cell function in response to cytokines is unknown. Here we demonstrate that I-BET, a BET protein inhibitor, protected {beta}-cells from cytokine induced dysfunction and death. In vivo administration of I-BET to mice exposed to low-dose STZ (streptozotocin), a model of T1D, significantly reduced {beta}-cell apoptosis and preserved {beta}-cell mass, suggesting a cytoprotective function of I-BET. Furthermore, human islets treated with I-BET displayed better glucose stimulated insulin secretion compared to controls, when exposed to cytokines. Mechanistically, RNA-Seq analysis revealed I-BET treatment suppressed pathways involved in apoptosis, including NF-kB signaling, while maintaining the expression of genes critical for {beta}-cell function, such as Pdx1 and Ins1. Taken together, this study demonstrates that I-BET is effective in protecting {beta}-cells from cytokine-induced dysfunction and apoptosis, and may have potential therapeutic values in T1D.

molecular biology↗

bioRxiv2020

Tead1 reciprocally regulates adult β-cell proliferation and function

Proliferative quiescence in {beta}-cells is required to maintain functional competence. While this presents a significant hurdle in regenerative therapy for diabetes, the molecular underpinnings of this reciprocal relationship remain unclear. Here, we demonstrate that TEAD1, the transcription effector of the mammalian-Hippo pathway, drives developmental stage-specific {beta}-cell proliferative capacity in conjunction with its functional maturation. TEAD1 promotes adult {beta}-cell mature identity by direct transcriptional control of a network of critical {beta}-cell transcription factors, including, Pdx1, Nkx6.1, and MafA, while its regulation of Cdkn2a maintains proliferative quiescence. Consequently, mice with either constitutive or inducible genetic deletion of TEAD1 in {beta}-cells developed overt diabetes due to a severe loss of secretory function despite induction of proliferation. Furthermore, we show that TEAD1 has a similar regulatory role in human {beta}-cells. Consistent with this function in {beta}-cells, variants in TEAD1 have been associated with c-HOMA-B in American Indians. We propose that TEAD1 is an essential intrinsic molecular switch coordinating adult {beta}-cell proliferative quiescence with mature identity and its differential modulation may be necessary to overcome the challenge of inducing proliferation with functional competence in human beta cells.

molecular biology↗