Analysis Tools
behavior/neurological
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• progressive worsening of motor performance with significantly reduced latency to fall off an accelerating rotating rod at 13 months of age
• significantly increased number of falls in the beam walking test at 13 months of age
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• progressive spastic gait disorder with cerebellar ataxia starting at 12 months of age, as quantified by the foot-base-angle at toe-off positions of the hindpaws which decreases with age, unlike in wild-type controls
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growth/size/body
weight loss
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J:228803
)
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• progressive reduction of body weight starting around 12 months of age, consistent with deterioration of overall health status
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nervous system
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• significantly reduced brain weight at 16 months of age
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• significantly reduced brain size at 16 months of age
• however, normal brain size and weight at 2 months of age
• no thinning of the corpus callosum at 16 months of age
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astrocytosis
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J:228803
)
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• activation of astrocytes in cortical and cerebellar neurons at 16 months of age, as shown by GFAP staining
• however, no evidence for astrocyte activation in the hippocampus, vestibular nuclei, inferior olivary nucleus, or spinal cord
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• axonal swelling filled with autophagic vesicles found in the corticospinal tract at 16 months of age
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• intraneuronal accumulation of autofluoerscent material in the cortex, cerebellum, and other CNS regions including the hippocampus, vestibular nuclei, inferior olivary nucleus, and spinal cord at 16 months of age
• cells accumulating autofluorescence co-label with beta-galactosidase, Ctip2, SatB2, parvalbumin or calbindin, suggesting that principal cells as well as inhibitory interneurons are affected
• large clusters of irregularly shaped electron-dense lipofuscin-like deposits and membranous structures filled with autophagic material are found in cortical, hippocampal pyramidal neurons, and spinal cord neurons at 16 months of age
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• marked accumulation of lipofuscin-like material in hippocampal pyramidal neurons at 16 months of age
• however, normal numbers of hippocampal pyramidal neurons at 16 months of age
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• large autofluorescent structures in Purkinje cells, often clustered, and surrounded by membranes that stain positive for the lysosomal marker protein Lamp1
• vesicular structure contents stain positive p62 (a receptor for cargo destined to be degraded by autophagy), suggesting that autofluorescent deposits represent undegraded autolysosomal material
• ultrastructural analysis of Purkinje cells shows clusters of vesicular structures filled with autophagic material as well as abnormally shaped electron-dense lipofuscin-like deposits, while only a few lipofuscin particles are found in wild-type controls
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• neuron loss in the cortex and the cerebellum is preceded by intraneuronal accumulation of autofluorescent material, and paralleled by the activation of astrocytes as shown by GFAP staining
• degenerating neurons accumulate abnormal autolysosomes and autolysosome-related autofluorescent material
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• severe loss of Purkinje cells by 16 months of age
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• significant loss of large projection neurons in cortical layers V and VI of the motor cortex at 16 months but not at 8 months of age
• normal neuron numbers in layers I-III (where most of the commissural neurons reside) at 16 months of age
• normal numbers of spinal cord motoneurons at 16 months of age
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• large diameter axon fibers are reduced by ~50% at 8 months and ~75% at 16 months in the lumbar corticospinal tract (L4), and by 56% at 16 months in the cervical corticospinal tract
• however, basic structure of motor endplates is relatively normal
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cellular
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• mutant MEFs display accumulation of autolysosomes (defined as vesicles labeled for both Lamp1 and p62) and decreased lysosome numbers (defined as Lamp1-positive vesicles that do not co-stain for p62) relative to wild-type MEFs
• upon induction of autophagy by serum starvation for 6 h, lysosomes are significantly depleted in both wild-type and mutant MEFs; however, after 14 h of starvation, lysosome numbers return to baseline levels only in wild-type while they remain diminished in mutant MEFs
• lysosome numbers are already reduced in Purkinje cells and cortical motoneurons at 2 months of age, prior to accumulation of autofluorescent material or any signs of neurodegeneration
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• mutant MEFs show increased levels of lipidated LC3 relative to wild-type MEFs, indicating impaired autolysosomal clearance; however, autophagy is not entirely blocked as LC3-II levels are further increased upon treatment with bafilomycin A1
• upon sustained (14 h) serum starvation, mutant MEFs show impaired recovery of lysosomes, consistent with a defect in autophagic lysosome reformation
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• mutant MEFs show an increased number of autolysosomes as well as increased levels of LC3-II (the lipidated form of LC3 recruited to autophagosomal membranes) relative to wild-type MEFs, indicating impaired autolysosomal clearance
• in mutant MEFs, LC3-II levels are further increased upon treatment with bafilomycin A1, which inhibits autolysosome acidification and autolysosomal degradation
• however, lysosomal processing of the lysosomal protease cathepsin D and intralysosomal pH are normal
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homeostasis/metabolism
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• mutant MEFs show increased levels of lipidated LC3 relative to wild-type MEFs, indicating impaired autolysosomal clearance; however, autophagy is not entirely blocked as LC3-II levels are further increased upon treatment with bafilomycin A1
• upon sustained (14 h) serum starvation, mutant MEFs show impaired recovery of lysosomes, consistent with a defect in autophagic lysosome reformation
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Mouse Models of Human Disease |
DO ID | OMIM ID(s) | Ref(s) | |
| hereditary spastic paraplegia 11 | DOID:0110764 |
OMIM:604360 |
J:228803 | |
