Evidence for three adult fast myosin heavy chain isoforms in type II skeletal muscle fibers in pigs

• Published in: Journal of animal science Vol. 76; no. 6; pp. 1584 - 1593
• Main Authors: Lefaucheur, L. (INRA, St-Gilles, France.), Hoffman, R.K, Gerrard, D.E, Okamura, C.S, Rubinstein, N, Kelly, A
• Format: Journal Article
• Language: English
• Published: Savoy, IL Am Soc Animal Sci 01.06.1998; American Society of Animal Science; Oxford University Press
• Subjects: ADN; Agricultural sciences; Amino Acid Sequence; AMINO ACID SEQUENCES; Animal production studies; Animals; Base Sequence; Biological and medical sciences; CERDO; CHEMICAL COMPOSITION; Chemistry; CLONACION; CLONAGE; CLONING; Cloning, Molecular; COMPLEMENTARY DNA; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; Conserved Sequence; DNA; DNA HYBRIDIZATION; FIBRAS MUSCULARES; FIBRE MUSCULAIRE; Fundamental and applied biological sciences. Psychology; Gene Expression; Gene Library; GLOBULINAS; GLOBULINE; GLOBULINS; HIBRIDACION DE ADN; Histocytochemistry; HISTOENZYMOLOGY; Humans; HYBRIDATION D'ADN; IMMUNOCYTOCHEMISTRY; Immunohistochemistry; IMMUNOLOGIE; IMMUNOLOGY; In Situ Hybridization - veterinary; INMUNOLOGIA; Isomerism; Life Sciences; LOCALIZATION; LONGISSIMUS; MOLECULAR HOMOLOGY; MOLECULAR SEQUENCE DATA; MUSCLE; MUSCLE FIBER TYPING; Muscle Fibers, Fast-Twitch - chemistry; MUSCLE FIBRES; MUSCLES; Muscular system; MUSCULOS; Myosin Heavy Chains - analysis; Myosin Heavy Chains - chemistry; Myosin Heavy Chains - genetics; NUCLEOTIDE SEQUENCE; PORCIN; Rats; Restriction Mapping - veterinary; RNA Probes - chemistry; RNA, Messenger - analysis; SECUENCIA NUCLEOTIDICA; SEMITENDINOSUS; Sequence Homology, Nucleic Acid; SEQUENCE NUCLEOTIDIQUE; Skeletal system; Space life sciences; Striated muscle. Tendons; SWINE; Swine - anatomy & histology; Swine - metabolism; Vertebrates: osteoarticular system, musculoskeletal system; Heavy peptide chain; Molecular form; Fast striated muscle; Contractile protein; Histology; Muscular fiber type II; Pig; Vertebrata; Mammalia; Myosin; Artiodactyla; Ungulata; Aminoacid sequence; Structural analysis
• ISSN: 0021-8812; 1525-3163; 0021-8812
• DOI: 10.2527/1998.7661584x

Three main fiber types one slow [type I] and two fast [type IIA and IIB] can be distinguished using conventional actomyosin ATPase (AM-ATPase) histochemistry after acidic pretreatment in mature pig skeletal muscle. We report the isolation, characterization, and identification of four adult 3'-untranslated regions corresponding to types I, IIA, IIB, and IIX myosin heavy chains (MyHC) from a cDNA library. Identification of different type II clones was based on sequence homology, in situ hybridizations (ISH), AM-ATPase histochemistry, and immunocytochemistry. Enzyme histochemistry, immunocytochemistry, and ISH were performed on serial transverse sections of longissimus and red portion of semitendinosus muscle. Results showed that all three fast MyHC transcripts were expressed in the longissimus, whereas only type IIA and IB transcripts were present in deep red semitendinosus muscle. Type I and IIA fibers contained mostly type I and IIA transcripts, respectively, whereas type IIB fibers contained a heterogeneous population of transcripts. In longissimus muscle, 18, 31, and 51% of conventional IIB fibers were pure IB, hybrid IIX/IIB. and pure IIB fibers, respectively. Conversely, conventional IIB fibers were actually IIX in deep red semitendinosus muscle. Expression of the three fast adult MyHC isoforms in longissimus was spatially regulated around the typical islets of type I fibers encountered in pig skeletal muscle. Thus, IIA fibers were contiguous to type I fibers, pure IIX fibers were in the direct vicinity of type I and IIA fibers, and hybrid IIX/IIB fibers were located mostly within primary fascicles between the islets of type I fibers; however, pure IIB fibers were located mainly at the periphery of the rosettes near the edges of primary fascicles. In light of the present study, conventional IIB fibers, as defined with AM-ATPase staining, are a heterogeneous population that should be split into pure IIX, hybrid IIX/IIB, and pure IIB fibers for a more accurate fi...