title: Forward Genetic Screen inCaenorhabditis elegansSuggests F57A10.2 and acp-4 As Suppressors of C9ORF72 Related Phenotypes.
abstract: An abnormally expanded GGGGCC repeat in C9ORF72 is the most frequent causal mutation associated with amyotrophic lateral sclerosis (ALS)/frontotemporal lobar degeneration (FTLD). Bothgain-of-function(gf) andloss-of-function(lf) mechanisms have been involved in C9ORF72 related ALS/FTLD. Thegfmechanism of C9ORF72 has been studied in various animal models but not inC. elegans. In the present study, we described mutant C9ORF72 modeling inC. elegansand report the finding of two suppressor genes. We made transgenes containing 9 or 29 repeats of GGGGCC in C9ORF72, driven by either thehsp-16promoters or theunc-119promoter. Transgenic worms were made to carry such transgenes. Phenotypic analysis of those animals revealed thatPhsp-16::(G4C2)29::GFPtransgenic animals (EAB 135) displayed severe paralysis by the second day of adulthood, followed by lethality, which phenotypes were less severe inPhsp-16::(G4C2)9::GFPtransgenic animals (EAB242), and absent in control strains expressing empty vectors. Suppressor genes of this locomotor phenotype were pursued by introducing mutations with ethyl methanesulfonate in EAB135, screening mutant strains that moved faster than EAB135 by a food-ring assay, identifying mutations by whole-genome sequencing and testing the underlying mechanism of the suppressor genes either by employing RNA interference studies orC. elegansgenetics. Three mutant strains, EAB164, EAB165 and EAB167, were identified. Eight suppressor genes carrying nonsense/canonical splicing site mutations were confirmed, among which a nonsense mutation of F57A10.2/VAMP was found in all three mutant strains, and a nonsense mutation of acp-4/ACP2 was only found in EAB164. Knock down/out of those two genes in EAB135 animals by feeding RNAi/introducing a known acp-4 null allele phenocopied the suppression of the C9ORF72 variant related movement defect in the mutant strains. Translational conformation in a mammalian system is required, but our worm data suggest that altering acp-4/ACP2 encoding lysosomal acid phosphatase may provide a potential therapeutic method of reducing acp-4/ACP2 levels, as opposed or complementary to directly reducing C9ORF72, to relieve C9ORF72-ALS phenotypes. It also suggests that the C9ORF72-ALS/FTLD may share a pathophysiologic mechanism with vesicle-associated membrane protein-associated protein B, a homolog of F57A10.2/VAMP, which is a proven ALS8 gene.
authors.affiliation: School of Public Health, Xinxiang Medical UniversityXinxiang, China; Program for Neuropsychiatric Research, McLean Hospital and Harvard Medical SchoolBelmont, MA, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Program for Neuropsychiatric Research, McLean Hospital and Harvard Medical School Belmont, MA, USA.
authors.forename: Limin
authors.initials: L
authors.lastname: Hao
authors.affiliation: Program for Neuropsychiatric Research, McLean Hospital and Harvard Medical School Belmont, MA, USA.
authors.forename: Taixiang
authors.initials: T
authors.lastname: Saur
authors.affiliation: Program for Neuropsychiatric Research, McLean Hospital and Harvard Medical School Belmont, MA, USA.
authors.forename: Katelyn
authors.initials: K
authors.lastname: Joyal
authors.affiliation: School of Pharmacy, Xinxiang Medical University Xinxiang, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Program for Neuropsychiatric Research, McLean Hospital and Harvard Medical School Belmont, MA, USA.
authors.forename: Desheng
authors.initials: D
authors.lastname: Zhai
authors.affiliation: Tianjin Mental Health Center Tianjin, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Li
authors.affiliation: Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Mochtar
authors.initials: M
authors.lastname: Pribadi
authors.affiliation: Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California, Los Angeles Los Angeles, CA, USA.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Coppola
authors.affiliation: Program for Neuropsychiatric Research, McLean Hospital and Harvard Medical School Belmont, MA, USA.
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Cohen
authors.affiliation: Program for Neuropsychiatric Research, McLean Hospital and Harvard Medical School Belmont, MA, USA.
authors.forename: Edgar A
authors.initials: EA
authors.lastname: Buttner
keywords: ACP2; ALS-FTLD; C9ORF72; Caenorhabditis elegans; VAPB; amyotrophic lateral sclerosis