Developmental effects on myonuclear domain size of rat diaphragm fibers

Carlos B. Mantilla, Rowan V. Sill, Bharathi Aravamudan, Wen Zhi Zhan, Gary C. Sieck

Research output: Contribution to journalArticle

30 Scopus citations

Abstract

During early postnatal development in rat diaphragm muscle (Dia m), significant fiber growth and transitions in myosin heavy chain (MHC) isoform expression occur. Similar to other skeletal muscles, Dia m fibers are multinucleated, and each myonucleus regulates the gene products within a finite volume: the myonuclear domain (MND). We hypothesized that postnatal changes in fiber cross-sectional area (CSA) are associated with increased number of myonuclei so that the MND size is maintained. The Dia m was removed at postnatal days 14 (P-14) and 28 (P-28). MHC isoform expression was determined by SDS-PAGE. Fiber CSA, myonuclear number, and MND size were measured using confocal microscopy. By P-14, significant coexpression of MHC isoforms was present with no fiber displaying singular expression of MHCNeo. By P-28, singular expression was predominant. MND size was not different across fiber types at P-14. Significant fiber growth was evident by P-28 at all fiber types (fiber CSA increased by 61, 93, and 147% at fibers expressing MHCSlow, MHC2A, and MHC2X, respectively). The number of myonuclei per unit of fiber length was similar across fibers at P-14, but it was greater at fibers expressing MHC2X at P-28. The total number of myonuclei per fiber also increased between P-14 and P-28 at all fiber types. Accordingly, MND size increased significantly by P-28 at all fiber types, and it became larger at fibers expressing MHC2X compared with fibers expressing MHCSlow or MHC2A. These results suggest that MND size is not maintained during the considerable fiber growth associated with postnatal development of the Diam.

Original languageEnglish (US)
Pages (from-to)787-794
Number of pages8
JournalJournal of applied physiology
Volume104
Issue number3
DOIs
StatePublished - Mar 1 2008

Keywords

  • Fiber type
  • Myosin heavy chain
  • Postnatal development
  • Respiratory muscles
  • Skeletal muscle

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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