Myosin Heavy Chain Expression Can Vary over the Length of Jaw and Leg Muscles

Abstract

Muscle fiber type classification can be determined by its myosin heavy chain (MyHC) composition based on a few consecutive sections. It is generally assumed that the MyHC expression of a muscle fiber is the same over its length since neural stimulation and systemic influences are supposed to be the same over its length. We analyzed this in detail in three muscle types: the temporalis (closer) and digastricus (opener; both first brachial arch), and the medial gastrocnemius (somite). Sections of the muscles were incubated with monoclonal antibodies against various MyHC isoforms, and the distribution of these isoforms within individual fibers was followed over a distance of approximately 1 mm. The staining intensity of a fiber was measured and compared with the other fibers in the section. In the temporalis, digastricus, and gastrocnemius, 46, 11, and 15%, respectively, of their MyHC-I fibers showed a variation in the staining intensity over the length of their fibers, as well as 47, 87, and 22%, respectively, of their MyHC-IIA fibers. Most variable fibers were found amongst those with an overall relative intermediate staining intensity, which are presumably hybrid fibers. We conclude that different parts of a muscle fiber can have different fiber type compositions and, thus, contractile properties. Some muscle parts might reach their maximum contraction peak sooner or later than a muscle part a few microns further away. Next to stimulation by the nerve and systemic influences, local influences might also have an impact on the MyHC expression of the fiber.

Modulation of Protein Quality Control and Proteasome to Autophagy Switch in Immortalized Myoblasts from Duchenne Muscular Dystrophy Patients

“…These results were confirmed by Western blot analysis of MyHC levels. Indeed, MyHC was expressed in each cell line, albeit to a higher degree in W2 and to a lower degree in D3 cell line ( Figure 1 B), a heterogeneity that was already reported in various muscle models [ 33 , 34 ]. We then tested for dystrophin expression, by Western blot analysis using mandra1 antibody that recognizes the end of the C-terminal domain of dystrophin.…”

Mixing it up: the biological significance of hybrid skeletal muscle fibers

“…4) (Zhang et al, 2010). Other more recent studies have reported similar patterns in normal mammalian muscles (Korfage et al, 2015;Zhang and Gould, 2017).…”

Segmental Distribution of Myosin Heavy Chain Isoforms Within Single Muscle Fibers

“…A regional variability of the distribution of MHC isoforms has been seen along the length of the global and orbital layers of human extraocular muscles, where MHC IIA and MHC I were most abundant on the proximal and distal ends (Park et al, ). This was also seen in the jaw and leg muscle from rabbits, where different parts of the fiber expressed different fiber type compositions and thus, different contractile properties (Korfage et al, ). Under certain circumstances (such as after spaceflight), single muscle fibers can simultaneously express as many as five MHC isoforms (Allen et al, ).…”