Cerebral palsy (CP) is a pediatric onset disorder with poorly understood molecular causes and progression, making early diagnosis difficult. Circular RNAs (circRNAs) are regulatory RNAs that show promise as biomarkers in various diseases but the role of circRNAs in CP is beginning to be understood. This study identified the role of circNFIX in regulating the expression of MEF2C, an important transcription factor for sarcomere development. We found that circNFIX is downregulated in the muscle cells of individuals with CP, and its localization shifts towards the nucleus as visualized using single molecule resolution imaging. The decreased expression of circNFIX, MEF2C, and MEF2C targets persisted throughout myoblasts to myotubes differentiation, and in the skeletal muscle tissue. Bioinformatic and experimental validation confirmed that circNFIX acts as a sponge for miR373-3p, a microRNA that represses MEF2C translation. In normal muscle, circNFIX de-represses MEF2C translation by sponging miR373-3p, allowing for normal sarcomere generation. In CP, reduced circNFIX expression results in loss of miRNA sponging, leading to lower MEF2C expression and downregulation of sarcomere genes, potentially causing shortened and dysfunctional muscle fibers. Knockdown of circNFIX (KD) reduced myogenic capacity of myoblasts to fuse and form myotubes similar to CP cells evident from the lower fusion index in CP and KD as compared to control myotubes. This the first study reporting reduction of MEF2C in CP and single molecule resolution imaging of circNFIX's subcellular distribution and its role in CP, suggesting circNFIX as a potential therapeutic target and biomarker for early CP diagnosis.

中文翻译：

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环状 RNA circNFIX 调节痉挛性脑瘫肌肉卫星细胞中 MEF2C 的表达。


脑瘫 （CP） 是一种儿科发病疾病，分子原因和进展知之甚少，因此难以早期诊断。环状 RNA （circRNA） 是调节 RNA，有望作为各种疾病的生物标志物，但 circRNA 在 CP 中的作用开始被了解。本研究确定了 circNFIX 在调节肌节发育的重要转录因子 MEF2C 表达中的作用。我们发现 circNFIX 在 CP 个体的肌肉细胞中下调，并且其定位向细胞核移动，如使用单分子分辨率成像所显示的那样。circNFIX 、 MEF2C 和 MEF2C 靶标的表达降低在整个成肌细胞到肌管分化以及骨骼肌组织中持续存在。生物信息学和实验验证证实，circNFIX 充当 miR373-3p 的海绵，miR373-3p 是一种抑制 MEF2C 翻译的 microRNA。在正常肌肉中，circNFIX 通过海绵 miR373-3p 去抑制 MEF2C 翻译，从而允许正常的肌节生成。在 CP 中，circNFIX 表达降低导致 miRNA 海绵丢失，导致 MEF2C 表达降低和肌节基因下调，可能导致肌纤维缩短和功能失调。敲除 circNFIX （KD） 降低了成肌细胞融合并形成类似于 CP 细胞的肌管的能力，与对照肌管相比，CP 和 KD 的融合指数较低，这很明显。这是第一项报告 CP 中 MEF2C 减少的研究和 circNFIX 亚细胞分布及其在 CP 中的作用的单分子分辨率成像，表明 circNFIX 是早期 CP 诊断的潜在治疗靶点和生物标志物。