Myotonic dystrophy type I (DM1) is a multisystemic autosomal-dominant inherited human disorder that is caused by CTG microsatellite repeat expansions (MREs) in the 3′ untranslated region of DMPK. Toxic RNAs expressed from such repetitive sequences can be eliminated using CRISPR-mediated RNA targeting, yet evidence of its in vivo efficacy and durability is lacking. Here, using adult and neonatal mouse models of DM1, we show that intramuscular or systemic injections of adeno-associated virus (AAV) vectors encoding nuclease-dead Cas9 and a single-guide RNA targeting CUG repeats results in the expression of the RNA-targeting Cas9 for up to three months, redistribution of the RNA-splicing protein muscleblind-like splicing regulator 1, elimination of foci of toxic RNA, reversal of splicing biomarkers and amelioration of myotonia. The sustained reversal of DM1 phenotypes provides further support that RNA-targeting Cas9 is a viable strategy for treating DM1 and other MRE-associated diseases.

强直性肌营养不良 I 型 (DM1) 是一种多系统常染色体显性遗传的人类疾病，由DMPK 3' 非翻译区的 CTG 微卫星重复扩增 (MRE) 引起. 使用 CRISPR 介导的 RNA 靶向可以消除从此类重复序列中表达的有毒 RNA，但缺乏其体内功效和持久性的证据。在这里，使用 DM1 的成年和新生小鼠模型，我们显示肌肉内或全身注射编码核酸酶死 Cas9 的腺相关病毒 (AAV) 载体和靶向 CUG 重复的单引导 RNA 会导致靶向 RNA 的表达Cas9 长达三个月，重新分布 RNA 剪接蛋白肌肉盲样剪接调节因子 1，消除有毒 RNA 的病灶，逆转剪接生物标志物和改善肌强直。DM1 表型的持续逆转进一步支持 RNA 靶向 Cas9 是治疗 DM1 和其他 MRE 相关疾病的可行策略。