Both neural factor(s) and muscle activity regulate the
developmental shift of myosin heavy chain mrna expression.
Camoretti-Mercado, Blanca, Yimin Qin, Smilja Jakovcic, Edgar Salazar
-Grueso, and Radovan Zak.
Departments of Medicine, Neurology, Organismal Biology and Anatomy
and the Pharmacological and Physiological Sciences, The University of
Chicago, Chicago, Illinois 60637
APStracts 3:0130C, 1996.
The adult ventricular isoform of chicken myosin heavy chain (MHC-V) is
transiently expressed in all skeletal muscle primordia analyzed, and
is completely repressed around embryonic days (E) 10-12, when
functional innervation is established. By RNase protection assay, we
demonstrated that denervation of the adult anterior latissimus dorsi
(ALD) muscle resulted in re-expression of MHC-V mRNA. In contrast,
treatment of primary cultures of fetal breast or leg muscles with
embryonic brain extract or conditioned media from glial or
neuroblastoma cell lines, but not from a myogenic cell line or
primary muscle cell cultures, led to inhibition of MHC-V expression.
This inhibitory activity was abolished by heating and increased with
protein concentration. The acquisition of both brain inhibitory
activity and the competence of myogenic cells to down-regulate MHC-V
mRNA expression were age-dependent. Furthermore, either paralysis of
muscle in ovo by curare, or contraction arrest of cultured myotubes
resulted in persistent expression of MHC-V mRNA. Thus, a putative
soluble factor(s) of nerve origin as well as muscle activity are
involved in the developmental down-regulation of MHC-V expression in
muscle primordia.
Received 10 October 1995; accepted in final form 10 April 1996.
APS Manuscript Number C609-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 May 96