Developmentally regulated expression of vascular smooth muscle myosin heavy chain isoforms

• Published in: The Journal of biological chemistry Vol. 264; no. 31; pp. 18272 - 18275
• Main Authors: Kuro-o, M, Nagai, R, Tsuchimochi, H, Katoh, H, Yazaki, Y, Ohkubo, A, Takaku, F
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 05.11.1989; American Society for Biochemistry and Molecular Biology
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Aorta; Biological and medical sciences; Contractile proteins; DNA Probes; Fluorescent Antibody Technique; Fundamental and applied biological sciences. Psychology; Gene Expression - physiology; Holoproteins; Immunoblotting; Muscle Development; Muscle, Smooth, Vascular - growth & development; Muscle, Smooth, Vascular - metabolism; Myosins - genetics; Nucleic Acid Hybridization; Proteins; Rabbits; RNA Splicing; RNA, Messenger - genetics; Embryonic development; Gel electrophoresis; heavy-Peptide chain; Rabbit; Contractile protein; Indirect immunofluorescence; Lagomorpha; Gene expression; Tissue; Vertebrata; Mammalia; Myosin; Immunoblotting assay; Aorta
• DOI: 10.1016/S0021-9258(18)51457-5
• ISSN: 0021-9258

Two types of smooth muscle myosin heavy chain (MHC) isoforms, SM1 and SM2, were recently identified to have different carboxyl termini (Nagai, R., Kuro-o, M., Babij, P., and Periasamy, M. (1989) J. Biol. Chem. 264, 9734-9737). SM1 and SM2 are considered to be generated from a single gene through alternative RNA splicing. In this study we investigated expression of vascular MHC isoforms during development in rabbits at the mRNA, protein, and histological levels. In adults, all smooth muscle cells reacted with both anti-SM1 and anti-SM2 antibodies on immunofluorescence, suggesting the coexpression of SM1 and SM2 in a single cell. In fetal and perinatal rabbits, however, only anti-SM1 antibody consistently reacted with smooth muscles. Reactivity with anti-SM2 antibody was negative in the fetal and neonatal blood vessels and gradually increased during 30 days after birth. These developmental changes in SM1 and SM2 expression at the histological level coincided with mRNA expression of each MHC isoform as determined by S1 nuclease mapping, indicating that expression of SM1 and SM2 is controlled at the level of RNA splicing. However, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of myosin from fetal and perinatal aortas revealed the presence of large amount of SM2. Interestingly, fetal SM2 did not cross-react with our anti-SM2 antibody on immunoblotting. We conclude that expression of SM1 and SM2 are differentially regulated during development and that a third type of MHC isoform may exist in embryonic and perinatal vascular smooth muscles.