Duchenne muscular dystrophy (DMD) is a progressive muscular disorder caused by an imbalance between muscle degeneration and regeneration resulting in muscle degeneration, necrosis, accumulation of fat and fibrosis, and insufficient regeneration/loss of myofibers. The genetic cause of DMD are mutations of the dystrophin muscular dystrophy gene (DMD) on the X chromosome. The Dmdmdx mutation in mice has a termination codon in exon 23 that is predicted to result in a truncated protein. Heterozygous females are viable and fertile with no gross phenotypic abnormalities. Homozygous females and hemizygous males are viable and fertile with myopathic features of DMD; although the myopathology is both less severe than the human disease course and variable by mouse strain genetic background.
The muscle pathology observed for C57BL/10ScSn-Dmdmdx mice (also referred to as C57BL/10-mdx ; Stock No. 001801) includes active fiber necrosis, cellular infiltration, a wide range of fiber sizes, and numerous centrally nucleated regenerating fibers. However, adult C57BL/10-mdx mice fail to exhibit several of the skeletal muscle characteristics of DMD (such as smaller number of myofibers, accumulation of fat and fibrosis, insufficient myofiber regeneration, and loss of muscle weight). In addition, the C57BL/10 inbred strain is shown to possess greater muscle satellite cell self-renewal ability/efficiency than that of the DBA/2 inbred strain which may increase muscle regeneration/attenuate muscular dystrophy phenotype for MD mutations maintained on the C57BL/10 genetic background. As such, The Jackson Laboratory Repository created this DBA/2J-congenic Dmdmdx mouse model, D2.B10-Dmdmdx/J (also referred to as DBA/2J-mdx or D2-mdx; Stock No. 013141).
These DBA/2J-mdx mice may be expected to have a phenotype similar to other Dmdmdx mouse models. That is, when compared to C57BL/10-mdx animals, DBA/2-congenic Dmdmdx mice exhibit additional DMD characteristics such as lower hind limb muscle weight, fewer myofibers, increased fibrosis and fat accumulation, and remarkable muscle weakness. The DBA/2-congenic Dmdmdx phenotype is attributed to diminished myofiber regeneration (rather than accelerated myofiber degeneration). Unlike C57BL/10-mdx mice, no increased incidence of spontaneous rhabdomyosarcoma-like tumors are reported for the DBA/2-congenic Dmdmdx model.
In an attempt to offer alleles on well-characterized or multiple genetic backgrounds, alleles are frequently moved to a genetic background different from that on which an allele was first characterized. This is the case for these DBA/2J-mdx mice (Stock No. 013141). It should be noted that the phenotype could vary from that originally described for C57BL/10-mdx (Stock No. 001801). We will modify the strain description if necessary as published results become available.
