ConditionalDystrophinablation in the skeletal muscle and brain causes profound effects on muscle function, neurobehavior, and extracellular matrix pathways
Authors: Karuppasamy Muthukumar , English Katherine G. , Conner James R. , Rorrer Shelby N. , Lopez Michael A. , Crossman David K. , Paul Jodi R. , Monreal-Gutierrez Miguel A. , Gamble Karen L. , Esser Karyn A. , Widrick Jeffrey J. , Kunkel Louis M. , Alexander Matthew S. 
Published: February 2025

Duchenne muscular dystrophy (DMD) patients suffer from skeletal and cardiopulmonary weakness, and interestingly up to one third are diagnosed on the autism spectrum. Dystrophin is an essential protein for regulating the transmission of intracellular force to the extracellular matrix within the skeletal muscle, but also plays key roles in neurobehavior and cognitive function. The mouse dystrophin gene (also abbreviatedDmd) is X-linked and has several isoforms with tissue-specific expression, including the largeDp427mmuscle transcript found in heart and skeletal muscle, and theDp427ctranscript that encodes the brain-specific dystrophin cerebellar protein. Understanding the functional requirements and pathways that are affected by dystrophin loss will impact dystrophin replacement gene therapy and exon-skipping correction strategies. We generated conditionalDystrophinknockout mice by targeting exon 52 of the mouseDystrophin(Dmdflox52) locus. We generated dystrophin constitutive and inducible myofiber knockout (DmdmKO) mice to evaluate the tissue-specific function of the large skeletal muscle dystrophin isoform. Constitutive embryonic deletion of theDystrophingene exclusively in skeletal myofibers resulted in a severe skeletal muscle myopathy, dystrophic histopathology, and functional deficits compared to themdxmouse. Transcriptomic analysis of skeletal myofibers of theDmdmKO mice revealed the dysregulation of key extracellular matrix and cytokine signaling pathways. Separately, we generated Purkinje neuron cerebellar dystrophin knockout (Dmd:Pcp2 KO) mice that displayed neurobehavioral deficits in social approach, social memory, and spatial navigation and working memory. These studies reveal the essential requirement for dystrophin expression in both the skeletal muscle and brain for normal physiological and neurobehavioral function.

Significance Statement

Duchenne muscular dystrophy is caused by the lack of a functional dystrophin protein in muscle. The large dystrophin (Dp427m) isoform is expressed in skeletal, cardiac, and smooth muscle, but its tissue-specific requirements remain unknown. We generated and characterized a conditional skeletal muscle knockout mouse (DmdmKO). Constitutive embryonic genetic ablation of skeletal muscleDystrophinresulted in muscle histopathologies similar to themdxmouse, while postnatal muscleDystrophinablation resulted in milder pathologies. Ablating cerebellarDystrophinDp427c using aPcp2/L7-Cre driver resulted in sociobehavioral defects. Transcriptomic analysis of theDmdmKO mice showed a severe reduction of extracellular matrix and cytokine signaling pathways. Our study reveals an essential role for skeletal muscle dystrophin and identifies essential pathways for modulation using dystrophin-replacement therapies.