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Dev Biol 2016 Aug 15;4162:373-88. doi: 10.1016/j.ydbio.2016.05.006.
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The cardiac-restricted protein ADP-ribosylhydrolase-like 1 is essential for heart chamber outgrowth and acts on muscle actin filament assembly.

Smith SJ , Towers N , Saldanha JW , Shang CA , Mahmood SR , Taylor WR , Mohun TJ .

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.

PubMed ID: 27217161
PMC ID: PMC4990356
Article link: Dev Biol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: acta4 actb actc1 actn1 adprh adprhl1 cfd lgals4.2 lyn mpo myh6 myl3 myl7 slc22a18
Antibodies: Adprhl1 Ab1 Myh6 Ab1
Morpholinos: adprhl1 MO1 adprhl1 MO2

Article Images: [+] show captions
References [+] :
Abu-Daya, Absence of heartbeat in the Xenopus tropicalis mutation muzak is caused by a nonsense mutation in cardiac myosin myh6. 2009, Pubmed, Xenbase