Knock-in Mouse Model of Hereditary Myopathy with Early Respiratory Failure Carrying the Titin Variant Corresponding to Human p.N31786K

Hereditary Myopathy with Early Respiratory Failure (HMERF) is a progressive titinopathy caused by dominant missense mutations in the A-band region of TTN , a domain essential for sarcomere stability. Patients suffering with HMERF manifest muscle weakness, early respiratory involvement, and reduced life expectancy, yet no effective therapies currently exist. A major barrier has been the lack of an animal model that replicated HMERF pathology. In this study, we established the first CRISPR-Cas9 engineered mouse model of HMERF, carrying a patient-derived missense mutation in Ttn . Homozygous mutant mice exhibited a severe and uniform phenotype, including kyphosis, thoracic deformities, abnormal gait, diaphragm weakness, and premature death. Histological analysis revealed disrupted sarcomeres, abnormal myotilin accumulation, and necklace-like cytoplasmic bodies in diaphragm muscle, resembling human pathology. Multi-omics approach revealed consistent dysregulation of genes and proteins linked to muscle structure, cytoskeletal integrity, and cellular homeostasis, representing disease pathomechanisms. A major limitation of this study was the restricted availability of muscle tissue, which prevented broader analysis across multiple muscle types. Nevertheless, overlapping transcriptomic and proteomic dysregulation, including differential splicing, highlight key molecular effects driving disease progression. In conclusion, this mouse model provides mechanistic insight into HMERF and establishes a platform for evaluating therapeutic strategies. It represents an essential step toward developing targeted interventions for this rare and severe neuromuscular disorder.