Mouse Genome Informatics
phenotype observed in females
phenotype observed in males
N normal phenotype
• most homozygotes die between 1 and 6 months of age

• unusual proliferation of sarcolemmal nuclei
• in contrast to wild-type, space between fibers is increased and an increase in interstitial tissue is observed
• in some cases, fat cells are found between fibers
• unusual proliferation of nuclei both within and between the fibers
• affected fibers appear rounded rather than polygonal in transverse section
• individual fibers exhibit size variations
• some fibers, although otherwise normal, contain long chains of centrally, rather than peripherally, located nuclei
• muscular atrophy proceeds from hind quarters to axial and forelimb musculature
• mild paralysis is first observed at 3.5 week and progresses to hindlimb dragging by 8 weeks
• eventually there is a complete loss of locomotor function and premature death

• observed at 8 weeks

• ataxia with occasional unilateral paresis is first observed at 3.5 weeks of age
• unilateral paresis begins at 3.5 weeks progressing to bilateral paresis
• paresis is accompanied by spasmodic flexion and flaccid extension in hindlimbs
• mild paralysis is first observed at 3.5 weeks and progresses to hindlimb dragging by 8 weeks
• failure to mate putatively due to physical disability
• gonad morphology is normal

• by two weeks of age, body weight is less than wildtype
• weight difference continues through out lifespan
• cachexia as well as thinning and ruffling of fur is observed by 8 weeks

Mouse Models of Human Disease
Muscular Dystrophy, Congenital Merosin-Deficient, 1A; MDC1A 607855 J:13125