Faculty Publications

Precardiac Mesoderm Differentiation In Vitro: Actin-isotype Synthetic Transitions, Myofibrillogenesis, Initiation of Heartbeat, and the Possible Involvement of Collagen

Document Type

Article

Journal/Book/Conference Title

Differentiation

Volume

28

Issue

1

First Page

62

Last Page

72

Abstract

The differentiation of precardiac mesoderm into beating heart tissue was examined during explant culture. Explanted tissue forms tubular heart-like vesicles and initiates rhythmic contractility within 18–24 h in vitro, a developmental time-course approximating that observed during in vivo development. Electron-microscopic observations reveal that beating heart cells are rich in cytoplasmic myofibrils in varying degrees of order, with some regions containing highly organized myofibrillar arrays. The analysis of actin-isotype biosynthesis, using metabolic labeling with [35S]-methionine and isoelectric-focusing resolution of the synthesized radioactive polypeptides, demonstrates that the initiation of cardiac α-actin synthesis and the pattern of transition in the synthesis of α-, β-, and γ-actin isotypes is equivalent to the initiation time and pattern observed in vivo. A possible collagen involvement in the differentiation process was investigated by assessing the effects of collagen-synthesis inhibitors on the development of the explant cultures. Two different agents, α,α′-dipyridyl and L-azetidine-2-carboxylic acid, exhibited a dose-dependent ability to inhibit the formation of beating heart tissue. When examined by electron microscopy, the nonbeating tissue exhibited a drastic depression of myofibrillogenesis, but otherwise appeared healthy. Further examination of the effect of L-azetidine-2-carboxylic acid demonstrated that the inhibition of myofibril formation and heartbeat was correlated with a 60% inhibition of native collagen synthesis; however, the time-course and pattern of actinisotype biosynthesis was completely unaffected. The data suggest a possible collagen involvement in heart differentiation that is necessary for either the synthesis of non-actin cardiac contractile proteins or the assembly of cardiac contractile proteins into myofibrils. © 1984, International Society of Differentiation. All rights reserved.

Department

Department of Biology

Original Publication Date

1-1-1984

DOI of published version

10.1111/j.1432-0436.1984.tb00267.x

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