Mice that are homozygous for the Smn1tm1Msd allele and hemizygous for the two transgenes, Tg(SMN2)11Tro and Tg(SMN2)46Tro, exhibit symptoms and neuropathology similar to patients afflicted with severe proximal spinal muscular atrophy (SMA). Triple mutants are indistinguishable from normal littermates in the first 4 days, after which they exhibit diminished weight gain. By 7 days of age, signs of muscle weakness are apparent and become progressively more pronounced over the following week as the mice display an abnormal gait. Mean survival is approximately 15 days although a few animals (&lt;3%) can survive longer. Histological analysis indicates that 15 day old mice have a reduced number of lumbar motor neurons and axons in sciatic nerve. Gastrocnemius muscles at the same age clearly show evidence of atrophy. Triple mutant mice develop progressive and severe necrotic lesions of the tail, ears and teeth. Mice hemizygous for both transgenes and heterozygous for the targeted mutation do not exhibit SMA-like phenotype. This mutant mouse strain may be useful in neuromuscular studies related to Spinal Muscular Atrophy (SMA).

Triple mutant mice that are homozygous for the Smn1tm1Msd allele and hemizygous for the two transgenes, Tg(SMN2)11Tro and Tg(SMN2)46Tro, exhibit diminished weight gain, progressive muscle weakness, necrotic lesions and loss of neurons in the sciatic nerve. This mutant mouse strain may be useful in neuromuscular studies related to Spinal Muscular Atrophy (SMA).

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