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Network analyses reveal novel aspects of ALS pathogenesis.

Sanhueza M, Chai A, Smith C, McCray BA, Simpson TI, Taylor JP, Pennetta G - PLoS Genet. (2015)

Bottom Line: Mutations in the human VAMP-associated protein B (hVAPB) cause a heterogeneous group of motor neuron diseases including ALS8.Identity markers of the endocytic process were also found to abnormally accumulate in ALS patients, further supporting the relevance of the fly data for human biology.Collectively, these results not only lead to a better understanding of hVAPB function but also point to potentially relevant targets for therapeutic intervention.

View Article: PubMed Central - PubMed

Affiliation: Centre for Integrative Physiology, University of Edinburgh, Edinburgh, United Kingdom; Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Edinburgh, United Kingdom.

ABSTRACT
Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by selective loss of motor neurons, muscle atrophy and paralysis. Mutations in the human VAMP-associated protein B (hVAPB) cause a heterogeneous group of motor neuron diseases including ALS8. Despite extensive research, the molecular mechanisms underlying ALS pathogenesis remain largely unknown. Genetic screens for key interactors of hVAPB activity in the intact nervous system, however, represent a fundamental approach towards understanding the in vivo function of hVAPB and its role in ALS pathogenesis. Targeted expression of the disease-causing allele leads to neurodegeneration and progressive decline in motor performance when expressed in the adult Drosophila, eye or in its entire nervous system, respectively. By using these two phenotypic readouts, we carried out a systematic survey of the Drosophila genome to identify modifiers of hVAPB-induced neurotoxicity. Modifiers cluster in a diverse array of biological functions including processes and genes that have been previously linked to hVAPB function, such as proteolysis and vesicular trafficking. In addition to established mechanisms, the screen identified endocytic trafficking and genes controlling proliferation and apoptosis as potent modifiers of ALS8-mediated defects. Surprisingly, the list of modifiers was mostly enriched for proteins linked to lipid droplet biogenesis and dynamics. Computational analysis reveals that most modifiers can be linked into a complex network of interacting genes, and that the human genes homologous to the Drosophila modifiers can be assembled into an interacting network largely overlapping with that in flies. Identity markers of the endocytic process were also found to abnormally accumulate in ALS patients, further supporting the relevance of the fly data for human biology. Collectively, these results not only lead to a better understanding of hVAPB function but also point to potentially relevant targets for therapeutic intervention.

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RAB5 accumulates in the cytoplasm of spinal cord neurons of patients with ALS.(A-C) Immuno-enzymatic detection of Rab5 in post-mortem tissues from ALS patients (B,C) and controls (A). RAB5 staining shows punctuate and diffuse distribution of immunoreactivity throughout the cytoplasm, whereas RAB5 accumulates in cytoplasmic clusters of spinal cord neurons of patients affected by ALS. (D-F) Immunofluorescence staining with anti-RAB5 and anti-hVAPB antibodies of spinal cord neurons from controls (D) and ALS patients (E and F). In ALS tissues, RAB5 redistributes to form clusters that overlap with hVAPB-positive immunoreactivity. Scale bar: 10μm.
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pgen.1005107.g008: RAB5 accumulates in the cytoplasm of spinal cord neurons of patients with ALS.(A-C) Immuno-enzymatic detection of Rab5 in post-mortem tissues from ALS patients (B,C) and controls (A). RAB5 staining shows punctuate and diffuse distribution of immunoreactivity throughout the cytoplasm, whereas RAB5 accumulates in cytoplasmic clusters of spinal cord neurons of patients affected by ALS. (D-F) Immunofluorescence staining with anti-RAB5 and anti-hVAPB antibodies of spinal cord neurons from controls (D) and ALS patients (E and F). In ALS tissues, RAB5 redistributes to form clusters that overlap with hVAPB-positive immunoreactivity. Scale bar: 10μm.

Mentions: We next performed immunohistochemistry on human post-mortem spinal cord tissue to determine whether RAB5 is present in motor neurons and whether its localization is affected in ALS. RAB5 is robustly expressed in spinal cord motor neurons and localizes to punctuate, granular pattern distributed throughout the cellular cytoplasm (Fig. 8A). Conversely, RAB5 localization in autopsy tissues from two sporadic ALS cases reveals an abnormal accumulation and clustering of RAB5 positive vesicles (Fig. 8B,C).


Network analyses reveal novel aspects of ALS pathogenesis.

Sanhueza M, Chai A, Smith C, McCray BA, Simpson TI, Taylor JP, Pennetta G - PLoS Genet. (2015)

RAB5 accumulates in the cytoplasm of spinal cord neurons of patients with ALS.(A-C) Immuno-enzymatic detection of Rab5 in post-mortem tissues from ALS patients (B,C) and controls (A). RAB5 staining shows punctuate and diffuse distribution of immunoreactivity throughout the cytoplasm, whereas RAB5 accumulates in cytoplasmic clusters of spinal cord neurons of patients affected by ALS. (D-F) Immunofluorescence staining with anti-RAB5 and anti-hVAPB antibodies of spinal cord neurons from controls (D) and ALS patients (E and F). In ALS tissues, RAB5 redistributes to form clusters that overlap with hVAPB-positive immunoreactivity. Scale bar: 10μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4380362&req=5

pgen.1005107.g008: RAB5 accumulates in the cytoplasm of spinal cord neurons of patients with ALS.(A-C) Immuno-enzymatic detection of Rab5 in post-mortem tissues from ALS patients (B,C) and controls (A). RAB5 staining shows punctuate and diffuse distribution of immunoreactivity throughout the cytoplasm, whereas RAB5 accumulates in cytoplasmic clusters of spinal cord neurons of patients affected by ALS. (D-F) Immunofluorescence staining with anti-RAB5 and anti-hVAPB antibodies of spinal cord neurons from controls (D) and ALS patients (E and F). In ALS tissues, RAB5 redistributes to form clusters that overlap with hVAPB-positive immunoreactivity. Scale bar: 10μm.
Mentions: We next performed immunohistochemistry on human post-mortem spinal cord tissue to determine whether RAB5 is present in motor neurons and whether its localization is affected in ALS. RAB5 is robustly expressed in spinal cord motor neurons and localizes to punctuate, granular pattern distributed throughout the cellular cytoplasm (Fig. 8A). Conversely, RAB5 localization in autopsy tissues from two sporadic ALS cases reveals an abnormal accumulation and clustering of RAB5 positive vesicles (Fig. 8B,C).

Bottom Line: Mutations in the human VAMP-associated protein B (hVAPB) cause a heterogeneous group of motor neuron diseases including ALS8.Identity markers of the endocytic process were also found to abnormally accumulate in ALS patients, further supporting the relevance of the fly data for human biology.Collectively, these results not only lead to a better understanding of hVAPB function but also point to potentially relevant targets for therapeutic intervention.

View Article: PubMed Central - PubMed

Affiliation: Centre for Integrative Physiology, University of Edinburgh, Edinburgh, United Kingdom; Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Edinburgh, United Kingdom.

ABSTRACT
Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by selective loss of motor neurons, muscle atrophy and paralysis. Mutations in the human VAMP-associated protein B (hVAPB) cause a heterogeneous group of motor neuron diseases including ALS8. Despite extensive research, the molecular mechanisms underlying ALS pathogenesis remain largely unknown. Genetic screens for key interactors of hVAPB activity in the intact nervous system, however, represent a fundamental approach towards understanding the in vivo function of hVAPB and its role in ALS pathogenesis. Targeted expression of the disease-causing allele leads to neurodegeneration and progressive decline in motor performance when expressed in the adult Drosophila, eye or in its entire nervous system, respectively. By using these two phenotypic readouts, we carried out a systematic survey of the Drosophila genome to identify modifiers of hVAPB-induced neurotoxicity. Modifiers cluster in a diverse array of biological functions including processes and genes that have been previously linked to hVAPB function, such as proteolysis and vesicular trafficking. In addition to established mechanisms, the screen identified endocytic trafficking and genes controlling proliferation and apoptosis as potent modifiers of ALS8-mediated defects. Surprisingly, the list of modifiers was mostly enriched for proteins linked to lipid droplet biogenesis and dynamics. Computational analysis reveals that most modifiers can be linked into a complex network of interacting genes, and that the human genes homologous to the Drosophila modifiers can be assembled into an interacting network largely overlapping with that in flies. Identity markers of the endocytic process were also found to abnormally accumulate in ALS patients, further supporting the relevance of the fly data for human biology. Collectively, these results not only lead to a better understanding of hVAPB function but also point to potentially relevant targets for therapeutic intervention.

Show MeSH
Related in: MedlinePlus