title: The cardiac-restricted protein ADP-ribosylhydrolase-like 1 is essential for heart chamber outgrowth and acts on muscle actin filament assembly.
abstract: Adprhl1, a member of the ADP-ribosylhydrolase protein family, is expressed exclusively in the developing heart of all vertebrates. In the amphibian Xenopus laevis, distribution of its mRNA is biased towards actively growing chamber myocardium. Morpholino oligonucleotide-mediated knockdown of all Adprhl1 variants inhibits striated myofibril assembly and prevents outgrowth of the ventricle. The resulting ventricles retain normal electrical conduction and express markers of chamber muscle differentiation but are functionally inert. Using a cardiac-specific Gal4 binary expression system, we show that the abundance of Adprhl1 protein in tadpole hearts is tightly controlled through a negative regulatory mechanism targeting the 5'-coding sequence of Xenopus adprhl1. Over-expression of full length (40kDa) Adprhl1 variants modified to escape such repression, also disrupts cardiac myofibrillogenesis. Disarrayed myofibrils persist that show extensive branching, with sarcomere division occurring at the actin-Z-disc boundary. Ultimately, Adprhl1-positive cells contain thin actin threads, connected to numerous circular branch points. Recombinant Adprhl1 can localize to stripes adjacent to the Z-disc, suggesting a direct role for Adprhl1 in modifying Z-disc and actin dynamics as heart chambers grow. Modelling the structure of Adprhl1 suggests this cardiac-specific protein is a pseudoenzyme, lacking key residues necessary for ADP-ribosylhydrolase catalytic activity.
authors.affiliation: Heart Formation in Vertebrates Laboratory, The Francis Crick Institute - Mill Hill Laboratory, The Ridgeway, Mill Hill, London NW7 1AA, UK.
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Smith
authors.affiliation: Heart Formation in Vertebrates Laboratory, The Francis Crick Institute - Mill Hill Laboratory, The Ridgeway, Mill Hill, London NW7 1AA, UK.
authors.forename: Norma
authors.initials: N
authors.lastname: Towers
authors.affiliation: Mathematical Biology Laboratory, The Francis Crick Institute - Mill Hill Laboratory, The Ridgeway, Mill Hill, London NW7 1AA, UK.
authors.forename: José W
authors.initials: JW
authors.lastname: Saldanha
authors.affiliation: Heart Formation in Vertebrates Laboratory, The Francis Crick Institute - Mill Hill Laboratory, The Ridgeway, Mill Hill, London NW7 1AA, UK.
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Shang
authors.affiliation: Experimental Histopathology, The Francis Crick Institute - Mill Hill Laboratory, The Ridgeway, Mill Hill, London NW7 1AA, UK.
authors.forename: S Radma
authors.initials: SR
authors.lastname: Mahmood
authors.affiliation: Mathematical Biology Laboratory, The Francis Crick Institute - Mill Hill Laboratory, The Ridgeway, Mill Hill, London NW7 1AA, UK.
authors.forename: William R
authors.initials: WR
authors.lastname: Taylor
authors.affiliation: Heart Formation in Vertebrates Laboratory, The Francis Crick Institute - Mill Hill Laboratory, The Ridgeway, Mill Hill, London NW7 1AA, UK. Electronic address: tim.mohun@crick.ac.uk.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Mohun
mesh_terms: D008841:Actin Cytoskeleton / Q000502:physiology*; D000818:Animals; D030801:Animals, Genetically Modified; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D006321:Heart / Q000196:embryology / Q000254:growth & development; D006352:Heart Ventricles / Q000196:embryology / Q000254:growth & development; D006801:Humans; D007814:Larva; D008164:Luminescent Proteins / Q000032:analysis / Q000235:genetics; D051379:Mice; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D060172:Morpholinos / Q000494:pharmacology; D009154:Mutation; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism; D009699:N-Glycosyl Hydrolases / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D038081:Organogenesis; D011487:Protein Conformation; D012333:RNA, Messenger / Q000096:biosynthesis; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029867:Xenopus Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D014982:Xenopus laevis / Q000196:embryology / Q000254:growth & development
chemical_list: D008164:Luminescent Proteins; D060172:Morpholinos; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D029867:Xenopus Proteins; C000619504:Adprhl1 protein, Xenopus; C000619532:Adprhl1 protein, human; C000619533:Adprhl1 protein, mouse; D009699:N-Glycosyl Hydrolases
keywords: Adprhl1; Heart; Morpholino; Myofibril; Transgenic; Ventricle