Paradoxical absence of M lines and downregulation of creatine kinase in mouse extraocular muscle

Francisco H. Andrade, Anita P. Merriam, Wei Guo, Georgiana Cheng, Colleen A. McMullen, Katrin Hayeß, Peter F.M. Van der Ven, John D. Porter

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


The M lines are structural landmarks in striated muscles, necessary for sarcomeric stability and as anchoring sites for the M isoform of creatine kinase (CK-M). These structures, especially prominent in fast skeletal muscles, are missing in rodent extraocular muscle, a particularly fast and active muscle group. In this study, we tested the hypotheses that 1) myomesin and M protein (cytoskeletal components of the M lines) and CK-M are downregulated in mouse extraocular muscle compared with the leg muscles, gastrocnemius and soleus; and 2) the expression of other cytosolic and mitochondrial CK isoforms is correspondingly increased. As expected, mouse extraocular muscles expressed lower levels of myomesin, M protein, and CK-M mRNA than the leg muscles. Immunocytochemically, myomesin and M protein were not detected in the banding pattern typically seen in other skeletal muscles. Surprisingly, message abundance for the other known CK isoforms was also lower in the extraocular muscles. Moreover, total CK activity was significantly decreased compared with that in the leg muscles. Based on these data, we reject our second hypothesis and propose that other energy-buffering systems may be more important in the extraocular muscles. The downregulation of major structural and metabolic elements and relative overexpression of two adenylate kinase isoforms suggest that the extraocular muscle group copes with its functional requirements by using strategies not seen in typical skeletal muscles.

Original languageEnglish
Pages (from-to)692-699
Number of pages8
JournalJournal of Applied Physiology
Issue number2
StatePublished - Aug 1 2003


  • Adenylate kinase
  • M protein
  • Myomesin
  • Oculomotor muscles

ASJC Scopus subject areas

  • General Medicine


Dive into the research topics of 'Paradoxical absence of M lines and downregulation of creatine kinase in mouse extraocular muscle'. Together they form a unique fingerprint.

Cite this