title: Molecular and functional alterations in a mouse cardiac model of Friedreich ataxia: activation of the integrated stress response, eIF2α phosphorylation, and the induction of downstream targets.
abstract: Friedreich ataxia (FA) is a neurodegenerative and cardiodegenerative disease resulting from marked frataxin deficiency. The condition is characterized by ataxia with fatal cardiomyopathy, but the pathogenic mechanisms are unclear. We investigated the association between gene expression and progressive histopathological and functional changes using the muscle creatine kinase conditional frataxin knockout (KO) mouse; this mouse develops a severe cardiac phenotype that resembles that of FA patients. We examined KO mice from 3 weeks of age, when they are asymptomatic, to 10 weeks of age, when they die of the disease. Positive iron staining was identified in KO mice from 5 weeks of age, with markedly reduced cardiac function from 6 weeks. We identified an early and marked up-regulation of a gene cohort responsible for stress-induced amino acid biosynthesis and observed markedly increased phosphorylation of eukaryotic translation initiation factor 2α (p-eIF2α), an activator of the integrated stress response, in KO mice at 3 weeks of age, relative to wild-type mice. Importantly, the eIF2α-mediated integrated stress response has been previously implicated in heart failure via downstream processes such as autophagy and apoptosis. Indeed, expression of a panel of autophagy and apoptosis markers was enhanced in KO mice. Thus, the pathogenesis of cardiomyopathy in FA correlates with the early and persistent eIF2α phosphorylation, which precedes activation of autophagy and apoptosis.
authors.affiliation: Molecular Pharmacology and Pathology Program, Department of Pathology, University of Sydney, Sydney, Australia.
authors.forename: Michael Li-Hsuan
authors.initials: ML
authors.lastname: Huang
authors.forename: Sutharshani
authors.initials: S
authors.lastname: Sivagurunathan
authors.forename: Samantha
authors.initials: S
authors.lastname: Ting
authors.forename: Patric J
authors.initials: PJ
authors.lastname: Jansson
authors.forename: Christopher J D
authors.initials: CJ
authors.lastname: Austin
authors.forename: Matthew
authors.initials: M
authors.lastname: Kelly
authors.forename: Christopher
authors.initials: C
authors.lastname: Semsarian
authors.forename: Daohai
authors.initials: D
authors.lastname: Zhang
authors.forename: Des R
authors.initials: DR
authors.lastname: Richardson
mesh_terms: D051701:Activating Transcription Factor 4 / Q000378:metabolism; D000596:Amino Acids / Q000096:biosynthesis; D000818:Animals; D017209:Apoptosis; D001343:Autophagy; D006332:Cardiomegaly / Q000473:pathology / Q000503:physiopathology; D004195:Disease Models, Animal; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D005260:Female; D005621:Friedreich Ataxia / Q000000981:diagnostic imaging / Q000235:genetics* / Q000473:pathology* / Q000503:physiopathology; D020869:Gene Expression Profiling; D006334:Heart Function Tests; D006801:Humans; D033862:Iron-Binding Proteins / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D032383:Myocytes, Cardiac / Q000201:enzymology / Q000473:pathology; D010641:Phenotype; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D013312:Stress, Physiological / Q000235:genetics; D014463:Ultrasonography; D000096923:Frataxin
chemical_list: D051701:Activating Transcription Factor 4; D000596:Amino Acids; D015852:Eukaryotic Initiation Factor-2; D033862:Iron-Binding Proteins; D011494:Protein Kinases; D000096923:Frataxin; C081452:Atf4 protein, mouse