Epigenetic signature during differentiation of presomitic satellite cells

The skeletal muscle adult stem cells (satellite cells SCs) are resident beneath basal lamina during entire life span and they are ready to activate themselves and regenerate new fibers. The SCs are responsible for muscle growth and preservation (Pietrangelo T et al, Exp Gerontol. 2009 44(8):523-31, 2009). The skeletal muscles are composed of different type of fibres that can be distinguished by their expression of particular isoforms of myosin heavy chain (MyHC) proteins. Moreover, the skeletal muscle fibres have different embriological origin, the extraocular (EOMs) and jaw-closer muscles develop from prechordal mesoderm rather than somites (limb and trunk muscles) and MyHC proteins are used to identify them (Hoh JF, Hughes S. J Muscle Res Cell Motil. 9(1):59-72, 1988; Maccatrozzo L et al, Genomics, 89(2):224-36, 2007; Toniolo L et al, Am J Physiol Cell Physiol. 2008 295(6): C1535-42, 2008). The different embriological origin of skeletal muscles could reflect the different regeneration/degeneration properties in healthy and/or chronic diseased muscles. We hypothesized that those differences may also endow the muscle associated satellite cells (SCs), responsible for muscle regeneration. The SCs were isolated from canine somitic (SDM) (Vastus Lateralis, Rectus Abdominus, Gluteus Superficialis, Biceps Femoris, Psoas) and presomitic (PSDM) (Lateral Rectus, Temporalis- M fiber, Retractor Bulbi and Masseter) muscles. We studied the proliferative and differentiative properties (population doubling level, fusion index, the expression of myogenic proteins, telomerase activity and skeletal muscle microRNA (myomiR) expression). We found interesting differences between somitic and presomitic satellite cells on differentiation ability.