title: Development transitions of thin filament proteins in rat extraocular muscles.
abstract: Extraocular muscles are a unique subset of striated muscles. During postnatal development, the extraocular muscles undergo a number of myosin isoform transitions that occur between postnatal day P10 (P10) and P15. These include: (1) loss of embryonic myosin from the global layer resulting in the expression restricted to the orbital layer; (2) the onset of expression of extraocular myosin and the putative tonic myosin (myh 7b/14); and (3) the redistribution of nonmuscle myosin IIB from a subsarcolemmal position to a sarcomeric distribution in the slow fibers of the global layer. For this study, we examined the postnatal appearance and distribution of α-actinin, tropomyosin, and nebulin isoforms during postnatal development of the rat extraocular muscles. Although sarcomeric α-actinin is detectable from birth, α-actinin 3 appears around P15. Both tropomyosin-1 and -2 are present from birth in the same distribution as in the adult animal. The expression of nebulin was monitored by gel electrophoresis and western blots. At P5-10, nebulin exhibits a lower molecular mass than observed P15 and later during postnatal development. The changes in α-actinin 3 and nebulin expression between P10 and P15 coincide with transitions in myosin isoforms as detailed above. These data point to P10-P15 as the critical period for the maturation of the extraocular muscles, coinciding with eyelid opening.
authors.affiliation: Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536, United States. cmonc2@uky.edu
authors.forename: Carole L
authors.initials: CL
authors.lastname: Moncman
authors.forename: Miguel E
authors.initials: ME
authors.lastname: Andrade
authors.forename: Andrea A
authors.initials: AA
authors.lastname: McCool
authors.forename: Colleen A
authors.initials: CA
authors.lastname: McMullen
authors.forename: Francisco H
authors.initials: FH
authors.lastname: Andrade
mesh_terms: D000185:Actinin / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D005260:Female; D009124:Muscle Proteins / Q000378:metabolism* / Q000502:physiology; D009210:Myofibrils / Q000378:metabolism* / Q000502:physiology; D009801:Oculomotor Muscles / Q000254:growth & development* / Q000378:metabolism / Q000648:ultrastructure; D011247:Pregnancy; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012518:Sarcomeres / Q000378:metabolism / Q000502:physiology; D014018:Tissue Distribution
chemical_list: D009124:Muscle Proteins; D020033:Protein Isoforms; D000185:Actinin