Assembly of thick, thin, and titin filaments in chick precardiac explants

Diane E. Rudy, Tatiana A. Yatskievych, Parker B. Antin, Carol C. Gregorio

Research output: Contribution to journalArticle

49 Scopus citations

Abstract

De novo cardiac myofibril assembly has been difficult to study due to the lack of available cell culture models that clearly and accurately reflect heart muscle development in vivo. However, within precardiac chick embryo ex-plants, premyocardial cells differentiate and commence beating in a temporal pattern that corresponds closely with myocyte differentiation in the embryo. Immunofluorescence staining of explants followed by confocal microscopy revealed that distinct stages of cardiac myofibril assembly, ranging from the earliest detection of sarcomeric proteins to the late appearance of mature myofibrils, were consistently recognized in precardiac cultures. Assembly events involved in the early formation of sarcomeres were clearly visualized and accurately reflected observations described by others during chick heart muscle development. Specifically, the early colocalization of α-actinin and titin dots was observed near the cell periphery representing I-Z -I-like complex formation. Myosin-containing thick filaments assembled independently of actin-containing thin filaments and appeared centered within sarcomeres when titin was also linearly aligned at or near cell borders. An N-terminal epitope of titin was detected earlier than a C-terminal epitope; however, both epitopes were observed to alternate near the cell periphery concomitant with the earliest formation of myofibrils. Although vascular actin was detected within cells during early assembly stages, cardiac actin predominated as the major actin isoform in mature thin filaments. Well-aligned thin filaments were also observed in the absence of organized staining for tropomodulin at thin filament pointed ends, suggesting that tropomodulin is not required to define thin filament lengths. Based on these findings, we conclude that the use of the avian precardiac explant system accurately allows for direct investigation of the mechanisms regulating de novo cardiac myofibrillogenesis.

Original languageEnglish (US)
Pages (from-to)61-71
Number of pages11
JournalDevelopmental Dynamics
Volume221
Issue number1
DOIs
StatePublished - Jan 1 2001

Keywords

  • Cardiomyocyte
  • Heart
  • Myofibril assembly
  • Precardiac explants
  • Sarcomere
  • Thick filament
  • Thin filament
  • Titin

ASJC Scopus subject areas

  • Developmental Biology

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