Jennings Katherine, Lindquist Diana, Poonia Ankita, Schoser Benedikt, Schneider-Gold Christiane, Timchenko Nikolai A, Timchenko Lubov
Division of Neurology, Cincinnati Children's Hospital, 3333 Burnet Ave, Cincinnati, OH 45229, United States.
Imaging Research Center, Cincinnati Children's Hospital, 3333 Burnet Ave, Cincinnati, OH 45229, United States.
Hum Mol Genet. 2025 Mar 7;34(6):512-522. doi: 10.1093/hmg/ddaf002.
Myotonic Dystrophy type 2 (DM2) is a multisystem disease affecting many tissues, including skeletal muscle, heart, and brain. DM2 is caused by unstable expansion of CCTG repeats in an intron 1 of a gene coding for cellular nuclear binding protein (CNBP). The expanded CCTG repeats cause DM2 pathology due to the accumulation of RNA CCUG repeats, which affect RNA processing in patients' cells. We have previously shown that mutant CCUG repeats reduce CNBP protein in DM2 patients. Reducing Cnbp in Cnbp KO mouse model causes late skeletal muscle atrophy. In this study, we examined if the reduction of Cnbp affects the Central Nervous System (CNS). MRI and DTI analyses showed that total brain volume and grey matter are reduced in Cnbp KO mice, while mean, radial and axonal brain diffusivity is increased. The morphological changes in the brains of Cnbp KO mice are accompanied by reduced stereotypic behavior, anxiety and neuromotor defects. These findings suggest that the reduction of CNBP contributes to CNS pathology in DM2. Since CNBP stability is regulated by pAMPK-dependent phosphorylation, we examined protein levels of pAMPK in DM2 cells and found that the active pAMPK is reduced in DM2. Interaction of CNBP with pAMPK and stability of CNBP protein are also decreased in DM2. Our data show that a small molecule AMPK activator A769662 corrects CNBP stability and normalizes CNBP targets in DM2 fibroblasts. Thus, activators of AMPK could potentially be developed as therapeutics to correct CNBP and reduce muscle and brain atrophies in DM2.
2型强直性肌营养不良症（DM2）是一种多系统疾病，会影响包括骨骼肌、心脏和大脑在内的许多组织。DM2是由编码细胞核结合蛋白（CNBP）的基因内含子1中CCTG重复序列的不稳定扩增引起的。扩增的CCTG重复序列导致DM2病理，这是由于RNA CCUG重复序列的积累，其影响患者细胞中的RNA加工。我们之前已经表明，突变的CCUG重复序列会降低DM2患者的CNBP蛋白水平。在Cnbp基因敲除小鼠模型中降低Cnbp会导致晚期骨骼肌萎缩。在本研究中，我们研究了Cnbp的减少是否会影响中枢神经系统（CNS）。MRI和DTI分析表明，Cnbp基因敲除小鼠的全脑体积和灰质减少，而平均、径向和轴突脑扩散率增加。Cnbp基因敲除小鼠大脑的形态变化伴随着刻板行为、焦虑和神经运动缺陷的减少。这些发现表明，CNBP的减少导致了DM2中的中枢神经系统病理。由于CNBP的稳定性受pAMPK依赖性磷酸化调节，我们检测了DM2细胞中pAMPK的蛋白水平，发现DM2中活性pAMPK减少。DM2中CNBP与pAMPK的相互作用以及CNBP蛋白的稳定性也降低。我们的数据表明，小分子AMPK激活剂A769662可纠正DM2成纤维细胞中CNBP的稳定性并使CNBP靶点正常化。因此，AMPK激活剂有可能被开发为治疗药物，以纠正CNBP并减少DM2中的肌肉和脑萎缩。
