Abstract: 15

MYO-D AS A MARKER FOR PROLIFERATING CELLS IN MUSCLES OF FETAL AND NEONATAL LAMBS.

SA McCoard^{1 2} , WC McNabb² , MJ Birtles¹ , PM Harris² , SN McCutcheon³ , SW Peterson¹
Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand ¹
AgResearch, Grasslands Research Institute, Private Bag 11008, Palmerston North, New Zealand ²
Vice Chancellor's Office, Massey University, Palmerston North, New Zealand ³

The relative role of myogenic precursor nuclei (MPN) in myofibre hypertrophy in late fetal and postnatal life is not well understood. This is primarily due to the lack of a reliable marker for these cells. The myogenic regulatory factor MyoD has been used as a marker for MPN in rodents, however, its usefulness in ovine tissue has not been described. Therefore, the first aim of this trial was to determine the usefulness of MyoD as an endogenous marker for the identification of MPN in ovine skeletal muscle tissue. Growth restriction in twin lambs, as compared to singles, is associated with lower skeletal muscle weights, smaller myofibre cross-sectional areas, and reduced muscle DNA contents, while myofibre complements are similar. This implies that myonuclei accumulation in ovine muscle is more important than myofibre number in determining muscle size in the fetal/neonatal lamb. Thus, the second aim of this study was to use MyoD as a marker to identify potential differences in the MPN numbers between selected skeletal muscles from single and twin fetuses/neonates. A double-labelling immunohistochemical technique using MyoD and the sarcolemma marker dystrophin, demonstrated that MyoD was a reliable endogenous marker for MPN in fetal and neonatal ovine skeletal muscle. Coupled with reduced total nuclei numbers, MyoD-positive nuclei were less abundant in hindlimb muscles of twins than singles suggesting differential effects on cell cycle activity. In addition, the pattern of expression of this factor during development suggests that MyoD may also have an important role in late fetal and postnatal muscle growth.

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.