title: Differential expression of calcineurin and SR Ca2+ handling proteins in equine muscle fibers during early postnatal growth.
abstract: During early postnatal development, the myosin heavy chain (MyHC) expression pattern in equine gluteus medius muscle shows adaptation to movement and load,resulting in a decrease in the number of fast MyHC fibers and an increase in the number of slow MyHC fibers. In the present study we correlated the expression of MyHC isoforms to the expression of sarcoplasmic(endo)reticulum Ca2+-ATPase 1 and 2a (SERCA), phospholamban (PLB), calcineurin A (CnA), and calcineurin B (CnB). Gluteus medius muscle biopsies were taken at 0, 2, 4, and 48 weeks and analyzed using immunofluorescence. Both SERCA isoforms and PLB were expressed in almost all fiber types at birth. From 4 weeks of age onward, SERCA1 was exclusively expressed in fast MyHC fibers and SERCA2a and PLB in slow MyHC fibers. At all time points, CnA and CnB proteins were expressed at a basal level in all fibers, but with a higher expression level in MyHC type 1 fibers. From 4 weeks onward, expression of only CnA was also higher in MyHC type 2a and 2ad fibers. We propose a double function of calcineurin in calcium homeostasis and maintenance of slow MyHC fiber type identity. Although equine muscle is already functional at birth, expression patterns of the monitored proteins still show adaptation, depending on the MyHC fiber type.
authors.affiliation: Department of Pathobiology, Division of Anatomy and Physiology, Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80.158, NL-3508 TD, Utrecht, The Netherlands. c.g.h.eizema@vet.uu.nl
authors.forename: Karin
authors.initials: K
authors.lastname: Eizema
authors.forename: Dianne E
authors.initials: DE
authors.lastname: van der Wal
authors.forename: Maarten M M
authors.initials: MM
authors.lastname: van den Burg
authors.forename: Henriëtte W
authors.initials: HW
authors.lastname: de Jonge
authors.forename: Maria E
authors.initials: ME
authors.lastname: Everts
mesh_terms: D000818:Animals; D019703:Calcineurin / Q000096:biosynthesis*; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000096:biosynthesis*; D005455:Fluorescent Antibody Technique; D006736:Horses; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D018482:Muscle, Skeletal / Q000254:growth & development / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000096:biosynthesis; D020033:Protein Isoforms / Q000096:biosynthesis; D021122:Protein Subunits / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000096:biosynthesis*; D000099211:Phospholamban
chemical_list: D019703:Calcineurin; D002118:Calcium; D002135:Calcium-Binding Proteins; D018995:Myosin Heavy Chains; D020033:Protein Isoforms; D021122:Protein Subunits; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000099211:Phospholamban