Expression of Unique and Developmental Myosin Heavy Chain Isoforms in Adult Human Digastric Muscle

Wang, Jun; Han, Yingshi; Su, Hungxi; Mu, Liancai

doi:10.1369/jhc.3a6136.2004

Cited by 13 publications

(36 citation statements)

References 44 publications

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“…Although this fiber type classification scheme has been demonstrated to correlate well with histochemical, biochemical, and physiological characteristics of different skeletal muscle fibers, its use in the fiber typing for the specialized cranial muscles may be limited. Our studies Wang et al, 2004;present study) and others have demonstrated that some cranial muscles contain unusual MHC isoforms. The presence or absence of the unusual MHC isoforms in the cranial muscle fibers cannot be detected by mATPase histochemistry.…”

Section: Fiber-type Classification For Cranial Musclessupporting

confidence: 67%

Adult human mylohyoid muscle fibers express slow‐tonic, α‐cardiac, and developmental myosin heavy‐chain isoforms

Wang

et al. 2004

Anat. Rec.

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Some adult cranial muscles have been reported to contain unusual myosin heavy-chain (MHC) isoforms (i.e., slow-tonic, ␣-cardiac, embryonic, and neonatal), which exhibit distinct contractile properties. In this study, adult human mylohyoid (MH) muscles obtained from autopsies were investigated to detect the unusual MHC isoforms. For comparison, the biceps brachii and masseter muscles of the same subjects were also examined. Serial cross-sections from the muscles studied were incubated with a panel of isoform-specific anti-MHC monoclonal antibodies that distinguish major and unusual MHC isoforms. On average, the slow type I and fast type II MHC-containing fibers in the MH muscle accounted for 54% and 46% of the fibers, respectively. In contrast to limb and trunk muscles, the adult human MH muscle was characterized by a large proportion of hybrid fibers (85%) and a small percentage of pure fibers (15%; P Ͻ 0.01). Of the fast fiber types, the proportion of the type IIa MHC-containing fibers (92%) was much greater than that of the type IIx MHC-containing fibers (8%; P Ͻ 0.01). Our data demonstrated that the adult human MH fibers expressed the unusual MHC isoforms that were also identified in the masseter, but not in the biceps brachii. These isoforms were demonstrated by immunocytochemistry and confirmed by electrophoretic immunoblotting. Fiber-to-fiber comparisons showed that the unusual MHC isoforms were coexpressed with the major MHC isoforms (i.e., MHCI, IIa, and IIx), thus forming various major/unusual (or m/u) MHC hybrid fiber types. Interestingly, the unusual MHC isoforms were expressed in a fiber type-specific manner. The slow-tonic and ␣-cardiac MHC isoforms were coexpressed predominantly with slow type I MHC isoform, whereas the developmental MHC isoforms (i.e., embryonic and neonatal) coexisted primarily with fast type IIa MHC isoform. There were no MH fibers that expressed exclusively unusual MHC isoforms. Approximately 81% of the slow type I MHC-containing fibers expressed slow-tonic and ␣-cardiac MHC isoforms, whereas 80% of the fast type IIa MHC-containing fibers expressed neonatal MHC isoform. The m/u hybrid fibers (82% of the total fiber population) were found to constitute the predominant fiber types in the adult human MH muscle. At least seven m/u MHC hybrid fiber types were identified in the adult human MH muscle. The most common m/u hybrid fiber types were found to be the MHCI/slow-tonic/␣-cardiac and MHCIIa/neonatal, which accounted for 39% and 33% of the total fiber population, respectively. The multiplicity of MHC isoforms in the adult MH fibers is believed to be related to embryonic origin, innervation pattern, and unique functional requirements.

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Section: Fiber-type Classification For Cranial Musclessupporting

confidence: 67%

Adult human mylohyoid muscle fibers express slow‐tonic, α‐cardiac, and developmental myosin heavy‐chain isoforms

Wang

et al. 2004

Anat. Rec.

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“…For example, MHC-toncontaining fibers common in lower vertebrates and birds (Hess 1970) have been found in extraocular muscles (Pierobon-Bormioli et al 1979;Sartore et al 1987), middle ear (Mascarello et al 1982), laryngeal muscles , masseter Ren and Mu 2005), suprahyoid muscles Wang et al 2004;Ren and Mu 2005), UES (present study), and in muscle spindles .…”

Section: Discussionsupporting

confidence: 55%

“…MHC-a, one of the major isoforms in the heart, has been identified in extraocular muscles (Wieczorek et al 1985;Pedrosa-Domellof et al 1992;Rushbrook et al 1994;Rubinstein and Hoh 2000), masseter (Bredman et al 1991;Pedrosa-Domellof et al 1992;Stal et al 1994;Kwa et al 1995;Korfage et al 2000;Mu et al 2004;Ren and Mu 2005), suprahyoid muscles Wang et al 2004;Ren and Mu 2005), UES (present study), and in muscle spindles (Michel et al 1996).…”

Section: Discussionsupporting

confidence: 55%

Adult Human Upper Esophageal Sphincter Contains Specialized Muscle Fibers Expressing Unusual Myosin Heavy Chain Isoforms

Wang

et al. 2006

J Histochem Cytochem.

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New Jersey (IS)S U M M A R Y The functional upper esophageal sphincter (UES) is composed of the cricopharyngeus muscle (CP), the most inferior part of the inferior pharyngeal constrictor (iIPC), and the upper esophagus (UE). This sphincter is collapsed and exhibits sustained muscle activity in the resting state; it only relaxes and opens during swallowing, vomiting, and belching. The tonic contractile properties of the UES suggest that the skeletal muscle fibers in this sphincter differ from those in the limb and trunk muscles. In this study, myosin heavy chain (MHC) composition in the adult human UES muscles obtained from autopsies was investigated using immunocytochemical and immunoblotting techniques. Results showed that the adult human UES muscle fibers expressed unusual MHC isoforms such as slow-tonic (MHC-ton), a-cardiac (MHC-a), neonatal (MHC-neo), and embryonic (MHC-emb), which coexisted with the major MHCs (i.e., MHCI, IIa, and IIx). MHC-ton and MHC-a were coexpressed predominantly with slow-type I MHC isoform, whereas MHC-neo and MHC-emb coexisted mainly with fast-type IIa MHC. A slow inner layer (SIL) and a fast outer layer (FOL) in the iIPC and CP were identified immunocytochemically. MHC-ton-and MHC-a-containing fibers were concentrated mainly in the SIL, whereas MHC-neo-and MHC-emb-containing fibers were distributed primarily to the FOL. Identification of the specialized muscle fibers and their distribution patterns in the adult human UES is valuable for a better understanding of the physiological and pathophysiological behaviors of the sphincter.(J Histochem Cytochem

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“…The three major MHCs in the muscle fibers were detected using ABC method as described (Mu et al, , 2007aWang et al, 2004;Ren and Mu, 2005;Mu and Sanders, 2007). Briefly, the serial cross-sections were (1) fixed in 4% paraformaldehyde for 10 min; (2) blocked in 2% bovine serum albumin (BSA) with 0.1% Triton X-100 for 20 min; (3) incubated with primary mAbs for 1 hr at room temperature (mAb NOQ7-5-4D) or overnight at 48C (mAbs MY-32 and SC-71); (4) incubated with a Vectastain anti-mouse IgG (ATCC, Rockville, MD) for 1 hr and reacted in ABC reagent for 1 hr; (5) reacted for 10 min with a solution containing 3,3 0 -diaminobenzidine (DAB) as chromogen to localize peroxidase for primary antibodies according to DAB substrate kit (SK-4100; Vector Laboratories, Burlingame, CA); and (6) dehydrated in graded concentrations of ethanol, cleared in xylene, and mounted with Permount.…”

Section: Histological and Immunocytochemical Proceduresmentioning

confidence: 99%

“…The unusual MHC isoforms in the muscle fibers were detected using indirect immunofluorescent staining as described (Mu et al, , 2007aWang et al, 2004;Ren and Mu, 2005;Mu and Sanders, 2007). Briefly, the sections adjacent to those stained with the ABC method were (1) fixed in 4% fresh paraformaldehyde for 10 min; (2) blocked in 2% BSA with 0.1% Triton X-100 for 20 min; (3) incubated with primary mAbs at 48C for either 12 hr (mAbs N2.261 and F1.652) or 24 hr (mAbs ALD-58 and BA-G5); (4) blocked again with 1% BSA for 5 min; (5) incubated in a fluorescein isothiocyanate-labeled goat anti-mouse IgG (FITC-GAM; 1:50 dilution; Sigma, St Louis, MO) for 1 hr; and (6) mounted with Vectashield mounting medium (Vector Laboratories) and kept in the dark at 48C.…”

Section: Histological and Immunocytochemical Proceduresmentioning

confidence: 99%

Newly Revealed Cricothyropharyngeus Muscle in the Human Laryngopharynx

Sanders

2008

The Anatomical Record

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Humans have a uniquely curved pharynx and tongue that is believed to have evolved for speech. The most inferior part of the pharynx consists of the laryngopharynx, the critical crossroad where swallowing, breathing, and phonation overlap. We hypothesized that the human laryngopharynx has unique neuromuscular specializations that may be speech related. Laryngopharynx specimens from 15 humans and 20 nonhuman mammals (dog, pig, rabbit, and rat) were studied. Microdissection revealed that only human specimens had a muscle originating from the anterior arch of the cricoid cartilage, and coursing between the inferior pharyngeal constrictor and cricopharyngeus muscles to insert into the median raphe at the posterior midline of the pharynx. On the basis of these anatomic features, we termed it the ''cricothyropharyngeus'' (CTP). The structure, innervation, and muscle fiber types of the human CTP were further investigated by histological methods, Sihler's stain, and myosin heavy chain (MHC) immunocytochemistry. The innervation and muscle fiber types of the CTP were found to differ from those of neighboring muscles. The laryngeal portion of the CTP was innervated by the external superior laryngeal nerve, whereas the pharyngeal portion of the muscle was supplied by the pharyngeal plexus. Most notable was that the CTP contained specialized muscle fibers expressing some unusual MHC isoforms (i.e., slow-tonic, a-cardiac, neonatal, and embryonic). In conclusion, the CTP appears to be a newly described and uniquely human muscle with characteristics suggesting a specialized function that may be speech related. Anat Rec, 291:927-938, 2008. 2008 Wiley-Liss, Inc.Key words: cricothyropharyngeus; laryngopharynx; innervation; MHC isoforms; fiber types; Sihler's stain; immunocytochemistry Laryngopharynx, the most inferior part of the pharynx, lies below the oropharynx and posterior to the larynx. It extends from the epiglottis superiorly down to the inferior border of the cricoid at C6. Laryngopharyngeal region is involved in important life-maintaining functions such as swallowing, respiration, and phonation. The muscles in this region have several special features. These features include that they are relatively small in size, organized into compartments, attached to the laryngeal cartilages (cricoid and thyroid cartilages), and innervated by different nerves (superior laryngeal nerve, recurrent laryngeal nerve, and

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Expression of Unique and Developmental Myosin Heavy Chain Isoforms in Adult Human Digastric Muscle

Cited by 13 publications

References 44 publications

Adult human mylohyoid muscle fibers express slow‐tonic, α‐cardiac, and developmental myosin heavy‐chain isoforms

Adult human mylohyoid muscle fibers express slow‐tonic, α‐cardiac, and developmental myosin heavy‐chain isoforms

Adult Human Upper Esophageal Sphincter Contains Specialized Muscle Fibers Expressing Unusual Myosin Heavy Chain Isoforms

Newly Revealed Cricothyropharyngeus Muscle in the Human Laryngopharynx

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