Expression of ADP-ribosylation enzymes in mouse embryos and muscle cell cultures

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Brooks, Benjamin
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Veterinary Anatomy, Pharmacology, and Physiology

Skeletal muscle myogenesis is a highly regulated process involving distinct changes in activation of transcription factors and gene expression driven by these transcription factors. Various regulatory signals from the local cellular environment play an important role in the commitment of cells to the myogenic pathway that eventually leads to terminal differentiation into multinucleated myotubes to form skeletal muscle. ADP-ribosylation activity has been detected in many avian and mammalian adult cardiac and skeletal muscle samples, but it is currently not known which enzymes are responsible for this activity, or if these same enzymes are expressed in the developing somites during embryogenesis. ADP-ribosylation has also been shown to be required for terminal differentiation in skeletal muscle cell cultures; however its mechanism of action has not been determined. This investigation examined the expression of the key ADP-ribosylation enzymes during embryo development in the mouse and during terminal differentiation in mouse C2C12 skeletal myoblast cell cultures. We also examined the effect of meta-Iodobenzylguanidine (MIBG), a known specific inhibitor of ADP-ribosyltransferase enzyme activity, on gene expression of select myogenic regulatory factors known to control terminal differentiation. The results demonstrated that Artl, Art3, Art5 and Adprh are expressed in the developing mouse embryos and that Art5 expression displayed the most restricted localization, mainly in the dorsal-medial lip of the dermamyotome, of the ADP-ribosylation enzymes. The localization of Art5 correlates with the known localization of integrin [alpha]7, a known substrate for ADP-ribosylation. Our investigations using C2C12 cell cultures as a model for terminal differentiation confirmed that MIBG inhibits differentiation of these cells. Inhibition with MIBG correlated with the failure to express Myodl, P21, and myogenin at distinct time points during the terminal differentiation process as compared to control treated cells. The expression of Artl, Art5 and Adprh were also shown to possess temporal patterns that were significantly affected by treatment with MIBG. Our results demonstrate the expression of key ADP-ribosylation enzymes during both somite development in the embryo and during terminal differentiation of C2C12 cell cultures. These data show that ADP-ribosylation may play an important role in determination and differentiation of skeletal muscle cells and that specific myogenic factors are regulated during differentiation by ADP-ribosylation.

Sun Jan 01 00:00:00 UTC 2006