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Phenotypes Associated with This Genotype
involves: 129P2/OlaHsd * FVB/N
Find Mice Using the International Mouse Strain Resource (IMSR)
Mouse lines carrying:
Smn1tm1Msd mutation (30 available); any Smn1 mutation (55 available)
Tg(SMN1*A2G)2023Ahmb mutation (3 available)
Tg(SMN2)89Ahmb mutation (27 available)
phenotype observed in females
phenotype observed in males
N normal phenotype
• mean survival is 227 days

nervous system
• 29% fewer lumbar spinal cord neurons than control in 3.5 month old mice
• 19% fewer facial nucleus neurons than control
• 5 day old mice did not exhibit reduced numbers of motor neurons
• ventral roots from L1-L5 lumbar spinal cord region contain few myelinated axons
• remaining axons are shriveled and exhibit Wallerian degeneration
• increased number of neuromuscular junctions in gastrocnemius
• intranuclear aggregates (gems) of the SMN protein in spinal cord are fewer and less intense than in normal littermates
• reduced amplitudes in evoked muscle potentials from tibial nerve
• axon sprouting occurs in gastrocnemius and triceps muscles
• sprouts are both nodal and emerge from the neuromuscular junction (terminal)

• angulated and atrophic fibers observed in gastrocnemius and to a lesser extent in quadriceps and intercostal muscles
• samples from multiple pelvic and thoracic muscles exhibit abnormal spontaneous activity of single muscle fibers and of motor units in 4-6 month old mice
• abnormal activity is occasionally accompanied by biphasic sharp waves

• 20-40% smaller than normal littermates
• toward the end of life

reproductive system

• mice fail to groom efficiently toward the end of life
• muscle weakness exhibited by 3 weeks of age
• mice are less active by 3 weeks of age compared to normal littermates
• exhibit very little activity toward the end of life

respiratory system
• mice exhibit short, shallow breeding toward the end of life

Mouse Models of Human Disease
OMIM ID Ref(s)
Spinal Muscular Atrophy, Type III; SMA3 253400 J:81238

Contributing Projects:
Mouse Genome Database (MGD), Gene Expression Database (GXD), Mouse Tumor Biology (MTB), Gene Ontology (GO), MouseCyc
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last database update
MGI 6.01
The Jackson Laboratory