Presence of SERCA and Calcineurin during Fetal Development of Porcine Skeletal Muscle
Henriëtte W. de Jonge 1*, Cornelia W. van der Wiel 1, Karin Eizema 1, Wim A. Weijs 1 and Maria E. Everts 1
1 Faculty of Veterinary Medicine, Department of Pathobiology, Division of Anatomy and Physiology, Utrecht University, Utrecht, The Netherlands
* To whom correspondence should be addressed. E-mail: h.w.dejonge{at}vet.uu.nl.
Submitted on August 12, 2005
Accepted on 24 December 2005
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Abstract |
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Mechanisms involved in skeletal myofiber differentiation during fetal development of large animals are poorly understood. Studies in small animals suggest that the calcineurin (Cn) pathway is involved in myofiber differentiation. Neural activity is a prerequisite for Cn activity, implying maintenance of sustained low intracellular Ca2+ concentrations. To study the role of Cn in fetal myofiber differentiation, we monitored the temporal and spatial distribution of Cn subunits, sarcoplasmic reticulum Ca2+ ATPase (SERCA), phospholamban (PLB) and myosin heavy chain (MyHC) isoforms in relation to ingrowing nerves in porcine m. semitendinosus at 55 and 75 days of gestation (dg) and at term. Immunofluorescence analysis revealed the presence of Cn subunits and SERCA isoforms at all analyzed stages. Cn distribution was not fiber type specific but expression became more prominent at term. At 75 dg differential SERCA2 expression was accompanied by perinuclear PLB in primary fibers. SERCA1 was expressed in all fiber types at all stages. No specific MyHC isoform distribution was seen in relation to neuromuscular contacts although neuromuscular contacts were present. From these results we speculate that in porcine m. semitendinosus differential SERCA2 expression precedes differential Cn expression. The question whether the Cn pathway is involved in prenatal myofiber differentiation needs further studies.
Key Words:
pig, myosin heavy chain, SERCA, PLB, calcineurin