Expression of myosin heavy chain isoforms in laryngeal muscles in comparison with skeletal and special muscles

Larynx in mammals is characterized by five intrinsic laryngeal muscles with complex movements involved in respiration, airway protection and phonation. These muscles, differently from limb and trunk muscles that derived from somites, originate from the branchial arches. In all species the laryngeal muscles have the capacity to express the transitional embryonic and perinatal isoforms in adult but at low level ([1-4]). In same species of mammals (horse and cow) the laryngeal muscles express only the three skeletal MyHC isoforms (type 1, 2A and 2X) ([3], [5]); other species (dog, cat and tiger) express also a faster isoform, not detectable in skeletal muscles, the 2B isoform [4,6,7]. Furthermore, in species where the 2B isoform is present in skeletal muscles (rat and rabbit), another isoform presumably faster is present, the EO MyHC ([8], [9]). In rat and human laryngeal muscles a different isoform (IIL MyHC) was described [10,11], but it is unclear if this new isoform correspond to EO in rat or to 2B in human or to the two novel isoforms identified by Rossi et al. [12] in EO muscles (codified by MYH 14 and 15 genes). Combining RNA expression, electrophoresis and immunoblot we demonstrated that the IIL isoform in human does not correspond to type 2 isoforms (2A, 2X, 2B, EO, embryonic and perinatal cluster), to cardiac isoforms (beta and alfa), to M isoform and to isoforms codified by MYH 14 and 15 gene, and therefore is probably a new isoform. [1] Jung HH, Han SH, Choi JO. Expression of myosin heavy chain mRNA in rat laryngeal muscles. Acta Otolaryngol. 1999; 119(3):396-402. [2] Malmgren LT, Lovice DB, Kaufman MR. Age-related changes in muscle fiber regeneration in the human thyroarytenoid muscle. Arch Otolaryngol Head Neck Surg. 2000; 126(7):851-6. [3] Toniolo L, Maccatrozzo L, Patruno M, Caliaro F, Mascarello F, Reggiani C. Expression of eight distinct MHC isoforms in bovine striated muscles: evidence for MHC-2B presence only in extraocular muscles. J Exp Biol. 2005; 208:4243-53. [4] Toniolo L, Maccatrozzo L, Patruno M, Pavan E, Caliaro F, Rossi R, Rinaldi C, Canepari M, Reggiani C, Mascarello F. Fiber types in canine muscles: myosin isoform expression and functional characterization. Am J Physiol Cell Physiol. 2007; 292(5):C1915-26. [5] Rhee HS, Steel CM, Derksen FJ, Robinson NE, Hoh JF. Immunohistochemical analysis of laryngeal muscles in normal horses and horses with subclinical recurrent laryngeal neuropathy. J Histochem Cytochem. 2009; 57(8):787-800. [6] Wu YZ, Baker MJ, Crumley RL, Blanks RH, Caiozzo VJ. A new concept in laryngeal muscle: multiple myosin isoform types in single muscle fibers of the lateral cricoarytenoid. Otolaryngol Head Neck Surg. 1998; 118(1):86-94. [7] Bergrin M, Bicer S, Lucas CA, Reiser PJ. Three-dimensional compartmentalization of myosin heavy chain and myosin light chain isoforms in dog thyroarytenoid muscle. Am J Physiol Cell Physiol. 2006; 290(5):C1446-58. [8] Lucas CA, Rughani A, Hoh JF. Expression of extraocular myosin heavy chain in rabbit laryngeal muscle. J Muscle Res Cell Motil. 1995; 16(4):368-78. [9] Briggs MM, Schachat F. Early specialization of the superfast myosin in extraocular and laryngeal muscles. J Exp Biol. 2000; 203:2485-94. [10] DelGaudio JM, Sciote JJ, Carroll WR, Escalmado RM. Atypical myosin heavy chain in rat laryngeal muscle. Ann Otol Rhinol Laryngol. 1995; 104(3):237-45. [11] Toniolo L, Macchi V, Porzionato A, Paoli A, Marchese-Ragona R, De Caro R, Reggiani C. Myosin heavy chain isoforms in human laryngeal muscles: an expression study based on gel electrophoresis. Int J Mol Med. 2008; 22(3):375-9. [12] Rossi AC, Mammucari C, Argentini C, Reggiani C, Schiaffino S. Two novel/ancient myosins in mammalian skeletal muscles: MYH14/7b and MYH15 are expressed in extraocular muscles and muscle spindles. J Physiol. 2010; 588:353-64.