Background: Duchenne muscular dystrophy (DMD) is characterized by muscle weakness, cardiac and respiratory abnormalities due to the mutation in the DMD gene that leads to the loss of a functional dystrophin protein. DMD is an X-linked disorder that affects boys at an incidence rate of 1:5000 live male births. Presently, no efficient conditional DMD mouse model exists to study the consequences of dystrophin loss in a tissue and temporal manner. Subsuquently, we generated and analyzed a conditional DMD mouse model to study the consequences of dystrophin loss in skeletal muscle lineages. This model targets exon 52 in the DMD gene and when mated to a muscle Cre recombinase transgenic mouse resulted in the loss of the major Dp427 muscle protein isoform.
Hypothesis: The DMD muscle knockout mouse model might have comparable DMD pathologies to human DMD patients and would be useful to examine dystrophin function in a tissue-specific manner. The histopathological, biochemical, and physiological features of conditional Dystrophin fl52/Y; HSA muscle knockout (Dmd fl52/Y; HSA mKO) mouse will have a severe muscle pathology similar to those observed in the mdx and mdx52 mouse models.
Methods: Using Cre/LoxP recombination system and CRISPR editing, we have generated Dmd flox52/Y that was mated to an HSA-Cre+ mouse model. The resulting Dmd flox52/Y; HSA mKO mice have been assessed using histopathological, phenotypical, functional and biochemical assays based on TREAT-NMD standard operating protocols (SOPs) for mdx mouse models for comparative analysis.
Results: Phenotypic analysis of these conditional mKO mice revealed a significant decline in locomotor activity and reduced muscle force, motor and muscular function as compared with Dystrophin mdx mice. The histochemical analysis revealed an increase in centralized myonuclei and fibrotic area similar to mdx mice.
Conclusions: This novel conditional Dmd flox52/Y; HSA mKO mouse model may offer invaluable insight into DMD disease pathology and possess the severe phenotype found in DMD patients. The generated mouse model could be advantageous in preclinical, dystrophin gene therapy and exon-skipping replacement studies.