Mechanisms underlying myosin heavy chain expression during development of the rat diaphragm muscle

• Published in: Journal of applied physiology (1985) 2006-12, Vol.101 (6), p.1546-1555
• Main Authors: Geiger, Paige C, Bailey, Jeffrey P, Mantilla, Carlos B, Zhan, Wen-Zhi, Sieck, Gary C
• Format: Article
• Language: English
• Subjects: Aging - physiology; Animals; Biological and medical sciences; Diaphragm - physiology; Enzymes; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Developmental - physiology; Male; Muscle Development - physiology; Myosin Heavy Chains - metabolism; Rats; Rats, Sprague-Dawley; Respiratory system; Ribonucleic acid; RNA; Rodents; Studies; Tissue Distribution
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00221.2006

Departments of 1 Physiology and Biomedical Engineering and 2 Anesthesiology, Mayo Clinic College of Medicine, Rochester, Minnesota Submitted 21 February 2006 ; accepted in final form 1 July 2006 During early postnatal development in rat diaphragm muscle (Dia m ), significant transitions in myosin heavy chain (MHC) isoform expression occur that are associated with fiber growth and increased MHC protein. At present, there is no direct information regarding the transcriptional regulation of MHC isoform expression during postnatal Dia m development. We hypothesized postnatal changes in MHC isoform mRNA expression are followed by concomitant changes in MHC protein expression. The Dia m was removed at postnatal days 0 , 14 , 28 , and 84 (adult). MHC mRNA expression was determined by real-time RT-PCR. MHC protein expression was determined by SDS-PAGE. There was a significant effect of postnatal age on MHC isoform mRNA and protein expression. At birth, the MHC Neo isoform accounted for 28% of MHC mRNA and 54% of total MHC protein. By postnatal day 14 , MHC Neo mRNA and protein increased significantly, and both decreased significantly by day 28 , consistent with transcriptional control of the expression of this developmental isoform. By postnatal day 28 , there were minimal changes in mRNA expression for MHC Slow and MHC 2X , yet protein expression increased significantly. MHC 2A mRNA and protein expression did not change during this time. Thus changes in MHC protein expression did not follow (or parallel) changes in MHC mRNA for the adult MHC isoforms. The present findings indicate that changes in MHC expression in the developing rat Dia m are not driven solely by changes in mRNA expression. Knowledge of isoform-specific MHC mRNA expression only yields predictive information on MHC protein expression for the MHC Neo isoform. real-time reverse transcriptase-polymerase chain reaction; electrophoresis; myosin heavy chain gene regulation; muscle plasticity Address for reprint requests and other correspondence: G. C. Sieck, Dept. of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905 (e-mail: sieck.gary{at}mayo.edu )