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Here we will focus on the two most popular animal models related to Duchenne, the mdx mouse and canine X-linked muscular dystrophy.
The mdx mouse
The mdx mouse, while not a precise model of human disease, is studied extensively by researchers interested in understanding muscle degeneration and regeneration in Duchenne. As a result, most experiments are performed on the mdx mouse.
The dystrophic mdx mouse has a point mutation within its dystrophin gene. This mutation has changed a codon representing glutamine amino acid to one representing thymine amino acid. This single amino acid change causes the cell’s machinery to stop; when this happens, the synthesis of dystrophin stops prematurely (known as premature stop codon). As a result, the mouse has no functional dystrophin in its muscles.
Early in life, the mdx mouse exhibits phases of marked skeletal muscle degeneration and subsequent regeneration; as it ages, certain muscle types such as the diaphragm show weakness and increased fibrosis.
Canine x-linked muscular dystrophy (CXMD, Golden Retriever MD, or GRMD)
A canine X-linked muscular dystrophy (GRMD) has been identified in a line of golden retrievers. As in Duchenne patients, the muscles of CXMD dogs lack dystrophin. These dogs develop severe weakness and muscle atrophy at about six to eight weeks of age. Degeneration of muscle fibers is common and heart problems are also present.
The GRMD represents the best model for Duchenne patients in terms of size and pathological expression of the disease.