The clostridium-like ecto-ADP-ribosyltransferase ARTC1 is expressed in a highly restricted manner in skeletal muscle and heart tissue. Although ARTC1 is well studied, the identification of ARTC1 targets in vivo and subsequent characterization of ARTC1-regulated cellular processes on the proteome level have been challenging and only a few ARTC1-ADP-ribosylated targets are known. Applying our recently developed mass spectrometry-based workflow to C2C12 myotubes and to skeletal muscle and heart tissues from wild-type mice, we identify hundreds of ARTC1-ADP-ribosylated proteins whose modifications are absent in the ADP-ribosylome of ARTC1-deficient mice. These proteins are ADP-ribosylated on arginine residues and mainly located on the cell surface or in the extracellular space. They are associated with signal transduction, transmembrane transport, and muscle function. Validation of hemopexin (HPX) as a ARTC1-target protein confirmed the functional importance of ARTC1-mediated extracellular arginine ADP-ribosylation at the systems level.

Transcriptome analysis allowed the identification of new long noncoding RNAs differentially expressed during murine myoblast differentiation. These transcripts were classified on the basis of their expression under proliferating versus differentiated conditions, muscle-restricted activation, and subcellular localization. Several species displayed preferential expression in dystrophic (mdx) versus wild-type muscles, indicating their possible link with regenerative processes. One of the identified transcripts, lnc-31, even if originating from the same nuclear precursor of miR-31, is produced by a pathway mutually exclusive. We show that lnc-31 and its human homologue hsa-lnc-31 are expressed in proliferating myoblasts, where they counteract differentiation. In line with this, both species are more abundant in mdx muscles and in human Duchenne muscular dystrophy (DMD) myoblasts, than in their normal counterparts. Altogether, these data suggest a crucial role for lnc-31 in controlling the differentiation commitment of precursor myoblasts and indicate that its function is maintained in evolution despite the poor sequence conservation with the human counterpart.

No abstract