Browsing by Author "Singh, Sandhya"

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    Musashi-2 causes cardiac hypertrophy and heart failure by inducing mitochondrial dysfunction through destabilizing Cluh and Smyd1 mRNA
    (Springer Nature Publishing AG, 2023) Singh, Sandhya; Gaur, Aakash; Sharma, Rakesh Kumar; Kumari, Renu; Prakash, Shakti; Kumari, Sunaina; Chaudhary, Ayushi Devendrasingh; Prasun, Pankaj; Pant, Priyanka; Hunkler, Hannah; Thum, Thomas; Jagavelu, Kumaravelu; Bharati, Pragya; Hanif, Kashif; Chitkara, Pragya; Kumar, Shailesh; Mitra, Kalyan; Gupta, Shashi Kumar
    Regulation of RNA stability and translation by RNA-binding proteins (RBPs) is a crucial process altering gene expression. Musashi family of RBPs comprising Msi1 and Msi2 is known to control RNA stability and translation. However, despite the presence of MSI2 in the heart, its function remains largely unknown. Here, we aim to explore the cardiac functions of MSI2. We confirmed the presence of MSI2 in the adult mouse, rat heart, and neonatal rat cardiomyocytes. Furthermore, Msi2 was significantly enriched in the heart cardiomyocyte fraction. Next, using RNA-seq data and isoform-specific PCR primers, we identified Msi2 isoforms 1, 4, and 5, and two novel putative isoforms labeled as Msi2 6 and 7 to be expressed in the heart. Overexpression of Msi2 isoforms led to cardiac hypertrophy in cultured cardiomyocytes. Additionally, Msi2 exhibited a significant increase in a pressure-overload model of cardiac hypertrophy. We selected isoforms 4 and 7 to validate the hypertrophic effects due to their unique alternative splicing patterns. AAV9-mediated overexpression of Msi2 isoforms 4 and 7 in murine hearts led to cardiac hypertrophy, dilation, heart failure, and eventually early death, confirming a pathological function for Msi2. Using global proteomics, gene ontology, transmission electron microscopy, seahorse, and transmembrane potential measurement assays, increased MSI2 was found to cause mitochondrial dysfunction in the heart. Mechanistically, we identified Cluh and Smyd1 as direct downstream targets of Msi2. Overexpression of Cluh and Smyd1 inhibited Msi2-induced cardiac malfunction and mitochondrial dysfunction. Collectively, we show that Msi2 induces hypertrophy, mitochondrial dysfunction, and heart failure.
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    The RNA-binding protein Quaking is essential for cardiac homeostasis and function by regulating Morf4l2 splicing
    (Elsevier B.V., 2026) Kumari, Sunaina; Shashi; Singh, Sandhya; Swain, Abinash; Prakash, Shakti; Chitkara, Pragya; Sharma, Rakesh Kumar; Agarwal, Pratyush; Kundu, Samprikta; Gaur, Aakash; Kumari, Renu; Sinha, Abhipsa; Chatterjee, Shambhabi; Prasun, Pankaj; Hummel, Oliver; Pant, Bhaskar; Srivastava, Kinshuk Raj; Hübner, Norbert; Datta, Dipak; Mitra, Kalyan; Mishra, Durga Prasad; Guha, Rajdeep; Thum, Thomas; Kumar, Shailesh; Gupta, Shashi Kumar
    Background: Lower levels of Qki were reported in human and mouse-failing hearts, implicating its involvement in cardiac diseases. However, the molecular and functional effects of its downregulation in adult myocardium remain largely unknown. Objective: We aim to uncover the effects of Qki knockdown in adult hearts. Methods & results: Here we show that AAV9-mediated knockdown of Qki by shRNAs in the hearts of adult BALB/c mice led to cardiac malfunction, atrophy, apoptosis, heart failure, and death within two weeks. Global transcriptomic analysis of Qki knockdown hearts revealed significant dysregulation of 996 alternative splicing events upon Qki knockdown. Mechanistically, we discovered that loss of Qki promotes the exclusion of the third exon of Morf4l2, leading to higher expression of exon three excluded variant (Morf4l2Δex3). Like rodents, the RNA-seq dataset from 108 human hearts revealed a lower splice junction count of MORF4L2 exon three in hearts with low levels of QKI compared to subjects with higher QKI levels. Specific knockdown of Morf4l2Δex3 rescues Qki knockdown-induced cardiac cachexia and improves cardiac function. Moreover, Morf4l2Δex3 was increased in the colon cancer-induced cardiac cachexia mouse model, and its inhibition prevented cardiac cachexia and improved cardiac function. Mechanistically, exon three of Morf4l2 lies in the 5'UTR, and its exclusion leads to higher expression of MORF4L2 upon Qki knockdown due to the lack of a G2-quadruplex. Importantly, MORF4L2 protein sequence and localization were not affected by alternative splicing as exon three lies in the 5'UTR. We found that MORF4L2 is a chromatin-bound protein and regulates H3K27ac. Conclusion: Qki knockdown in the adult heart leads to cardiac cachexia due to the alteration of Morf4l2 splicing. Inhibition of Morf4l2Δex3 inhibits cancer-induced cardiac cachexia, demonstrating it as a potential therapeutic target.