Therapeutic genetics and disease modeling in LAMA2-CMD

点击翻译按钮获取中文摘要

ABSTRACT Muscular dystrophies impact an estimated 250,000 patients in the United States, resulting in an annual medical expenditure of over $46 billion. The economic loss is more substantial in the congenital-onset muscular dystrophies (CMDs), which manifest very early in life, due to patients' inability to enter the workforce and/or their premature death. LAMA2-deficient congenital muscular dystrophy (LAMA2-CMD), the most common form of CMD, is caused by mutations in the LAMA2 gene encoding the LAMA2 protein. The lack of LAMA2 protein causes degeneration of skeletal muscle and impaired Schwann cell myelination, resulting in a cascade of secondary events that include apoptosis, inflammation, and fibrosis, which ultimately precipitate the disease. Patients are provided with disease symptom management, such as assisted ventilation, ambulatory services, and physiotherapy to reduce contractures, but there is no curative option. Owing to the genetic nature of the disease, the correction of mutations would be a promising treatment for LAMA2-CMD. We have previously described the use of CRISPR/Cas9 to correct a splice site mutation in the Lama2 gene and showed amelioration of disease phenotypes in a LAMA2-CMD mouse model. However, there are more than 600 pathogenic mutations identified in the patient populations, which significantly hampers future translation of any LAMA2 mutation correction strategy to patients. In contrast, the attenuation of disease pathogenicity by targeted modulation of the expression of disease modifier genes would be beneficial to all individuals affected with LAMA2-CMD. We were the first to develop a CRISPR activation-based approach to postnatally upregulate a disease modifier gene Lama1, which is structurally and functionally similar to Lama2, in the mouse model. These findings led to the hypothesis that targeted LAMA1 gene activation can serve as a mutation-independent therapeutic approach for LAMA2-CMD. We will test this hypothesis by performing a dedicated preclinical evaluation of efficacy and safety profiles of Lama1 upregulation in a severe LAMA2-CMD mouse model. In addition, we will bridge the translation of the strategy from a mouse-to patient-relevant models and evaluate the effect of human LAMA1 upregulation on cellular impairments, including mitochondrial respiration, migration, and myelination. Successful completion of these experiments will pave the way towards the development of mutation-independent therapeutic interventions for LAMA2-CMD and potentially other muscular dystrophies.