Distribution of fast myosin heavy chain isoforms in thick filaments of developing chicken pectoral muscle.

Abstract

Abstract. Colloidal gold-conjugated monoclonal antibodies were prepared to stage-specific fast myosin heavy chain (MHC) isoforms of developing chicken pectoralis major (PM). Native thick filaments from different stages of development were reacted with these antibodies and examined in the electron microscope to determine their myosin isoform composition. Filaments prepared from 12-d embryo, 10-d chick, and 1-yr chicken muscle specifically reacted with the embryonic (EB165), neonatal (2E9), and adult (AB8) antimyosin gold-conjugated monoclonal antibodies, respectively. The myosin isoform composition was more complex in thick filaments from stages of pectoral muscle where more than one isoform was simultaneously expressed. In 19-d embryo muscle where both embryonic and neonatal isoforms were present, three classes of filaments were found. One class of filaments reacted only with the embryonic antibody, a second class reacted only with the neonatal-specific antibody, and a third class of filaments were decorated by both antibodies. Similar results were obtained with filaments prepared from 44-d chicken PM where the neonatal and adult fast MHCs were expressed. These observations demonstrate that two myosin isoforms can exist in an individual thick filament in vivo. Immunoelectron microscopy was also used to determine the specific distribution of different fast MHC isoforms within individual filaments from different stages of development. The anti-embryonic and anti-adult antibodies uniformly decorated both homogeneous and heterogeneous thick filaments. The neonatal specific antibody uniformly decorated homogeneous filaments; however, it preferentially decorated the center of heterogeneous filaments. These observations suggest that neonatal MHC may play a specific role in fibrillogenesis.

Myosin isoform switching during assembly of the Drosophila flight muscle thick filament lattice

“…Transitions in myosin isoforms during development, such as from embryonic and neonatal to adult myosin isoforms, have been demonstrated in various vertebrate striated muscles, such as rat (Whalen et al, 1981;Lyons et al, 1983, Weydert et al, 1987Lyons et al, 1990;LaFramboise et al, 1991;Hughes et al, 1993) and chicken pectoral muscle (Taylor and Bandman, 1989). In the latter case, individual thick filaments containing both neonatal and adult isoforms were documented.…”

Three distinct sarcomeric patterns of skeletal muscle revealed by SHG and TPEF Microscopy

“…It has also been suggested, in body wall muscles of C. elegans, that a non uniform distribution of myosin heavy chain isoforms along each thick filament could explain the central dip of the sarcomeric SHG signal since the isoform with the lowest SHG efficiency is localized at the center of the A-band [1,3]. Non uniform distribution of myosin heavy chain isoforms has also been shown in chicken pectoralis thick filaments [28]. However in vertebrates (including xenopus and rats) the effect of such asymmetric distribution on the sarcomeric SHG intensity still needs to be studied.…”

Subcellular localization of newly incorporated myosin in rabbit fast skeletal muscle undergoing stimulation-induced type transformation

“…Taylor and Bandman (1989) used gold-conjugated antibodies to study the myosin transitions that occur in chicken pectoralis major muscle during development, in the course of which embryonic myosin is replaced by myosin isoforms of the neonatal and adult type. Native thick filaments could be isolated from muscles of 19-day embryos which contained epitopes of both embryonic and neonatal myosin, with the latter distributed preferentially in a central region of the filaments.…”