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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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Enhancers of the DVAP-P58S eye phenotype.(A) Stereomicroscope images of adult fly eyes from controls (ey-Gal4/+), flies expressing DVAP-P58S in the eye (ey,DVAP-P58S), flies expressing DVAP-P58S in the presence of an heterozygous overexpression allele of the representative enhancer CaBP1EY12345 (ey,DVAP-P58S/CaBP1EY12345) and flies overexpressing CaBP1EY12345 under the control of the ey-Gal4 driver (ey/CaBP1EY12345). (B) Estimated eye surface area phenotype presented as scatter plots. Red horizontal lines represent the average surface area of the indicated genotypes. (C) Quantification of the eye surface areas and lethality of modifiers with an enhancing activity. See Materials and Methods for the calculation of the lethality and the eye surface areas of every enhancer. Reported data result from at least three independent experiments. ***P<0.001. n = at least 15 flies per genotype. Scale bar: 50μm.
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pgen.1005107.g002: Enhancers of the DVAP-P58S eye phenotype.(A) Stereomicroscope images of adult fly eyes from controls (ey-Gal4/+), flies expressing DVAP-P58S in the eye (ey,DVAP-P58S), flies expressing DVAP-P58S in the presence of an heterozygous overexpression allele of the representative enhancer CaBP1EY12345 (ey,DVAP-P58S/CaBP1EY12345) and flies overexpressing CaBP1EY12345 under the control of the ey-Gal4 driver (ey/CaBP1EY12345). (B) Estimated eye surface area phenotype presented as scatter plots. Red horizontal lines represent the average surface area of the indicated genotypes. (C) Quantification of the eye surface areas and lethality of modifiers with an enhancing activity. See Materials and Methods for the calculation of the lethality and the eye surface areas of every enhancer. Reported data result from at least three independent experiments. ***P<0.001. n = at least 15 flies per genotype. Scale bar: 50μm.

Mentions: Fig. 1A depicts light micrographs of representative eye phenotypes of one suppressor and Fig. 1B shows scatter plots of actual surface areas for the same suppressor. Fig. 1C presents average surface areas of every suppressor resulting from a set of three independent experiments. In Fig. 2, results of a representative enhancer (Fig. 2A,B) and data on the effect of the remaining enhancers for viability and eye neurodegenerative phenotypes are presented (Fig. 2C). The complete list of all suppressors is reported in S1 Table together with the percentage of modifying activity of every modifier. S2 Table reports genes with an enhancing effect on both the eye and organismal lethality phenotypes.


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)

Enhancers of the DVAP-P58S eye phenotype.(A) Stereomicroscope images of adult fly eyes from controls (ey-Gal4/+), flies expressing DVAP-P58S in the eye (ey,DVAP-P58S), flies expressing DVAP-P58S in the presence of an heterozygous overexpression allele of the representative enhancer CaBP1EY12345 (ey,DVAP-P58S/CaBP1EY12345) and flies overexpressing CaBP1EY12345 under the control of the ey-Gal4 driver (ey/CaBP1EY12345). (B) Estimated eye surface area phenotype presented as scatter plots. Red horizontal lines represent the average surface area of the indicated genotypes. (C) Quantification of the eye surface areas and lethality of modifiers with an enhancing activity. See Materials and Methods for the calculation of the lethality and the eye surface areas of every enhancer. Reported data result from at least three independent experiments. ***P<0.001. n = at least 15 flies per genotype. Scale bar: 50μm.
© Copyright Policy
Related In: Results  -  Collection

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

pgen.1005107.g002: Enhancers of the DVAP-P58S eye phenotype.(A) Stereomicroscope images of adult fly eyes from controls (ey-Gal4/+), flies expressing DVAP-P58S in the eye (ey,DVAP-P58S), flies expressing DVAP-P58S in the presence of an heterozygous overexpression allele of the representative enhancer CaBP1EY12345 (ey,DVAP-P58S/CaBP1EY12345) and flies overexpressing CaBP1EY12345 under the control of the ey-Gal4 driver (ey/CaBP1EY12345). (B) Estimated eye surface area phenotype presented as scatter plots. Red horizontal lines represent the average surface area of the indicated genotypes. (C) Quantification of the eye surface areas and lethality of modifiers with an enhancing activity. See Materials and Methods for the calculation of the lethality and the eye surface areas of every enhancer. Reported data result from at least three independent experiments. ***P<0.001. n = at least 15 flies per genotype. Scale bar: 50μm.
Mentions: Fig. 1A depicts light micrographs of representative eye phenotypes of one suppressor and Fig. 1B shows scatter plots of actual surface areas for the same suppressor. Fig. 1C presents average surface areas of every suppressor resulting from a set of three independent experiments. In Fig. 2, results of a representative enhancer (Fig. 2A,B) and data on the effect of the remaining enhancers for viability and eye neurodegenerative phenotypes are presented (Fig. 2C). The complete list of all suppressors is reported in S1 Table together with the percentage of modifying activity of every modifier. S2 Table reports genes with an enhancing effect on both the eye and organismal lethality phenotypes.

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