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.

RNA 结合蛋白 (RBP) 对 RNA 稳定性和翻译的调节是改变基因表达的关键过程。 Musashi 家族 RBP 包含Msi1和Msi2 ，已知可控制 RNA 稳定性和翻译。然而，尽管心脏中存在 MSI2，但其功能仍然很大程度上未知。在这里，我们的目的是探讨 MSI2 的心脏功能。我们证实成年小鼠、大鼠心脏和新生大鼠心肌细胞中存在 MSI2。此外， Msi2在心脏心肌细胞部分中显着富集。接下来，使用 RNA-seq 数据和异构体特异性 PCR 引物，我们鉴定了Msi2异构体 1、4 和 5，以及标记为Msi2 6 和 7 的两种新的假定异构体，将在心脏中表达。 Msi2同种型的过度表达导致培养的心肌细胞中的心脏肥大。此外， Msi2在心脏肥大的压力超负荷模型中表现出显着增加。我们选择同工型 4 和 7 来验证其独特的选择性剪接模式的肥大效应。 AAV9介导的Msi2亚型4和7在小鼠心脏中的过度表达导致心脏肥大、扩张、心力衰竭，并最终早期死亡，证实了Msi2的病理功能。使用全局蛋白质组学、基因本体论、透射电子显微镜、海马和跨膜电位测量分析，发现 MSI2 增加会导致心脏线粒体功能障碍。从机制上讲，我们将Cluh和Smyd1确定为Msi2的直接下游靶标。 Cluh和Smyd1的过度表达抑制Msi2诱导的心脏功能障碍和线粒体功能障碍。总的来说，我们发现Msi2会诱导肥大、线粒体功能障碍和心力衰竭。