title: Developmental myosins: expression patterns and functional significance.
abstract: Developing skeletal muscles express unique myosin isoforms, including embryonic and neonatal myosin heavy chains, coded by the myosin heavy chain 3 (MYH3) and MYH8 genes, respectively, and myosin light chain 1 embryonic/atrial, encoded by the myosin light chain 4 (MYL4) gene. These myosin isoforms are transiently expressed during embryonic and fetal development and disappear shortly after birth when adult fast and slow myosins become prevalent. However, developmental myosins persist throughout adult stages in specialized muscles, such as the extraocular and jaw-closing muscles, and in the intrafusal fibers of the muscle spindles. These myosins are re-expressed during muscle regeneration and provide a specific marker of regenerating fibers in the pathologic skeletal muscle. Mutations in MYH3 or MYH8 are responsible for distal arthrogryposis syndromes, characterized by congenital joint contractures and orofacial dysmorphisms, supporting the importance of muscle contractile activity and body movements in joint development and in shaping the form of the face during fetal development. The biochemical and biophysical properties of developmental myosins have only partially been defined, and their functional significance is not yet clear. One possibility is that these myosins are specialized in contracting against low loads, and thus, they may be adapted to the prenatal environment, when fetal muscles contract against a very low load compared to postnatal muscles.
authors.affiliation: Venetian Institute of Molecular Medicine (VIMM), Via G. Orus 2, 35129 Padova, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Schiaffino
authors.affiliation: Department of Molecular, Cellular and Developmental Biology and BioFrontiers Institute, University of Colorado, Boulder, CO USA.
authors.forename: Alberto C
authors.initials: AC
authors.lastname: Rossi
authors.affiliation: Institute of Anatomy, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
authors.forename: Vika
authors.initials: V
authors.lastname: Smerdu
authors.affiliation: Department of Molecular, Cellular and Developmental Biology and BioFrontiers Institute, University of Colorado, Boulder, CO USA.
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Leinwand
authors.affiliation: Department of Biomedical Sciences, University of Padova, Padova, Italy ; CNR Institute of Neuroscience, Padova, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Reggiani
keywords: Distal arthrogryposis; Embryonic myosin; Muscle development; Muscle regeneration; Myosin heavy chain; Neonatal myosin