Impaired vitamin D signaling causes LMNA mutation-related cardiomyopathy

Mutations of the lamin A/C gene (LMNA) cause a variety of diseases including dilated cardiomyopathy (DCM). LMNA-related DCM often leads to severe heart failure, but the underlying pathophysiology is unknown. Here we show that vitamin D receptor (VDR) signaling is critically involved in LMNA-related DCM. We established iPS cells from DCM patients with an LMNA mutation and found that the iPS cell-derived cardiomyocytes (iPSCMs) showed remarkable DNA damage and reduced contractility compared with the isogenic control. Screening of a chemical library revealed that vitamin D2 reduced DNA damage of the mutant iPSCMs. RNA sequencing analysis showed that expression levels of putative downstream genes of VDR including DNA repair factors were downregulated in the mutant iPSCMs, which were upregulated by vitamin D2. Protein-protein interaction screening revealed that the binding of VDR to mutant LMNA was more robust than to wild-type LMNA, resulting in attenuated VDR signaling in the mutant iPSCMs. Vitamin D2 administration reduced DNA damage and improved cardiac function in pressure overload-induced heart failure mice. These results indicate that impaired DNA repair caused by reduced transcriptional activity of VDR induces cardiac dysfunction of LMNA-related DCM and suggest that VDR signaling is a potential therapeutic target for patients with DCM and heart failure. Overall design: Bulk RNA-seq analysis in LMNA mutant iPS cell-derived cardiomyocytes.

核纤层蛋白A/C基因（lamin A/C gene, LMNA）的突变可引发包括扩张型心肌病（dilated cardiomyopathy, DCM）在内的多种疾病。LMNA相关扩张型心肌病常导致严重心力衰竭，但其潜在病理生理机制至今尚未阐明。本研究证实，维生素D受体（vitamin D receptor, VDR）信号通路在LMNA相关扩张型心肌病中发挥关键调控作用。
我们从携带LMNA突变的扩张型心肌病患者体内构建了诱导多能干细胞（induced pluripotent stem cells, iPS），并发现该类干细胞分化而来的心肌细胞（iPS cell-derived cardiomyocytes, iPSCMs）相较于同基因对照细胞，出现了显著的DNA损伤，且收缩功能明显受损。
化学小分子文库筛选结果显示，维生素D2可有效降低突变型iPSCMs的DNA损伤水平。RNA测序分析表明，突变型iPSCMs中包括DNA修复因子在内的VDR潜在下游基因的表达水平显著下调，而维生素D2处理可显著上调这些基因的表达。蛋白质相互作用筛选实验证实，突变型LMNA与VDR的结合亲和力高于野生型LMNA，进而导致突变型iPSCMs中VDR信号通路活性被削弱。向压力负荷诱导的心力衰竭小鼠给予维生素D2，可降低其体内DNA损伤水平并改善心功能。
上述研究结果表明，VDR转录活性降低所引发的DNA修复功能受损，可诱发LMNA相关扩张型心肌病的心功能障碍，同时提示VDR信号通路可作为扩张型心肌病及心力衰竭患者的潜在治疗靶点。
整体实验设计：对携带LMNA突变的iPS细胞分化心肌细胞开展批量RNA测序（bulk RNA-seq）分析。