Glycogen storage disease type III (GSDIII) is a rare inborn error of metabolism affecting liver, skeletal muscle, and heart due to mutations of the AGL gene encoding for the glycogen debranching enzyme (GDE). No curative treatment exists for GSDIII. The 4.6 kb GDE cDNA represents the major technical challenge toward the development of a single recombinant adeno-associated virus–derived (rAAV-derived) vector gene therapy strategy. Using information on GDE structure and molecular modeling, we generated multiple truncated GDEs. Among them, an N-terminal–truncated mutant, ΔNter2-GDE, had a similar efficacy in vivo compared with the full-size enzyme. A rAAV vector expressing ΔNter2-GDE allowed significant glycogen reduction in heart and muscle of Agl^–/– mice 3 months after i.v. injection, as well as normalization of histology features and restoration of muscle strength. Similarly, glycogen accumulation and histological features were corrected in a recently generated Agl^–/– rat model. Finally, transduction with rAAV vectors encoding ΔNter2-GDE corrected glycogen accumulation in an in vitro human skeletal muscle cellular model of GSDIII. In conclusion, our results demonstrated the ability of a single rAAV vector expressing a functional mini-GDE transgene to correct the muscle and heart phenotype in multiple models of GSDIII, supporting its clinical translation to patients with GSDIII.

中文翻译：

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功能性迷你 GDE 转基因可纠正 III 型糖原累积病模型中的损伤

III 型糖原贮积病 (GSDIII) 是一种罕见的先天性代谢缺陷，由于编码糖原脱支酶 (GDE) 的AGL基因突变而影响肝脏、骨骼肌和心脏。GSDIII 尚无治愈方法。4.6 kb GDE cDNA 代表了开发单一重组腺相关病毒衍生（rAAV 衍生）载体基因治疗策略的主要技术挑战。利用 GDE 结构和分子建模的信息，我们生成了多个截断的 GDE。其中，N端截短的突变体ΔNter2-GDE与全尺寸酶相比具有相似的体内功效。表达 ΔNter2-GDE 的 rAAV 载体在静脉注射 3 个月后，使Agl ^–/–小鼠的心脏和肌肉糖原显着减少，组织学特征正常化并恢复肌肉力量。同样，在最近生成的Agl ^–/–大鼠模型中，糖原积累和组织学特征也得到了纠正。最后，用编码 ΔNter2-GDE 的 rAAV 载体转导纠正了 GSDIII 体外人骨骼肌细胞模型中的糖原积累。总之，我们的结果证明了表达功能性迷你 GDE 转基因的单个 rAAV 载体能够纠正多种 GSDIII 模型中的肌肉和心脏表型，支持其临床转化为 GSDIII 患者。