Immunohistochemical analysis of the effects of cross-innervation of murine thyroarytenoid and sternohyoid muscles.
This work uses cross-innervation of respiratory muscles of different developmental origins to probe myogenic and neurogenic mechanisms regulating their fiber types. The thyroarytenoid (TA) originates from the sixth branchial arch, whereas the sternohyoid (SH) is derived from somitic mesoderm. Immunohistochemical analysis using highly specific monoclonal antibodies to myosin heavy chain (MyHC) isoforms reveals that normal rat SH comprises slow, 2a, 2x, and 2b fibers, as in limb fast muscles, whereas the external division of the TA has only 2b/eo fibers coexpressing 2B and extraocular (EO) MyHCs. Twelve weeks after cross-innervation with the recurrent laryngeal nerve, the SH retained slow and 2a fibers, greatly increased the proportion of 2x fibers, and their 2b fibers failed to express EO MyHC. In the cross-innervated TA, the SH nerve failed to induce slow and 2A MyHC expression and failed to suppress EO MyHC expression in 2b/eo fibers. However, 2x fibers amounting to 4.2% appeared de novo in the external division of the TA. We conclude that although MyHC gene expression in these muscles can be modulated by neural activity, the patterns of response to altered innervation are largely myogenically determined, thus supporting the idea that SH and TA differ in muscle allotype.
Rhee
Hannah S
HS
Discipline of Physiology, Building F13, Sydney Medical School, The University of Sydney, Sydney, New South Wales 2006, Australia.
Hoh
Joseph F Y
JF
D000818:Animals; D005260:Female; D007150:Immunohistochemistry; D007823:Laryngeal Nerves / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D009334:Neck Muscles / Q000294:innervation* / Q000378:metabolism*; D020033:Protein Isoforms / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D020033:Protein Isoforms; D018995:Myosin Heavy Chains