Limits...
Two novel/ancient myosins in mammalian skeletal muscles: MYH14/7b and MYH15 are expressed in extraocular muscles and muscle spindles.

Rossi AC, Mammucari C, Argentini C, Reggiani C, Schiaffino S - J. Physiol. (Lond.) (2009)

Bottom Line: During development, MYH14 is expressed at low levels in skeletal muscles, heart and all EO muscle fibres but disappears from most fibres, except the slow-tonic fibres, after birth.In contrast, MYH15 is absent in embryonic and fetal muscles and is first detected after birth in the orbital layer of EO muscles.The identification of the expression pattern of MYH14 and MYH15 brings to completion the inventory of the MYH isoforms involved in sarcomeric architecture of skeletal muscles and provides an unambiguous molecular basis to study the contractile properties of slow-tonic fibres in mammals.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Sciences, University of Padova, Padova, Italy.

ABSTRACT
The mammalian genome contains three ancient sarcomeric myosin heavy chain (MYH) genes, MYH14/7b, MYH15 and MYH16, in addition to the two well characterized clusters of skeletal and cardiac MYHs. MYH16 is expressed in jaw muscles of carnivores; however the expression pattern of MYH14 and MYH15 is not known. MYH14 and MYH15 orthologues are present in frogs and birds, coding for chicken slow myosin 2 and ventricular MYH, respectively, whereas only MYH14 orthologues have been detected in fish. In all species the MYH14 gene contains a microRNA, miR-499. Here we report that in rat and mouse, MYH14 and miR-499 transcripts are detected in heart, slow muscles and extraocular (EO) muscles, whereas MYH15 transcripts are detected exclusively in EO muscles. However, MYH14 protein is detected only in a minor fibre population in EO muscles, corresponding to slow-tonic fibres, and in bag fibres of muscle spindles. MYH15 protein is present in most fibres of the orbital layer of EO muscles and in the extracapsular region of bag fibres. During development, MYH14 is expressed at low levels in skeletal muscles, heart and all EO muscle fibres but disappears from most fibres, except the slow-tonic fibres, after birth. In contrast, MYH15 is absent in embryonic and fetal muscles and is first detected after birth in the orbital layer of EO muscles. The identification of the expression pattern of MYH14 and MYH15 brings to completion the inventory of the MYH isoforms involved in sarcomeric architecture of skeletal muscles and provides an unambiguous molecular basis to study the contractile properties of slow-tonic fibres in mammals.

Show MeSH

Related in: MedlinePlus

Scheme illustrating the evolutionary relationships among sarcomeric MYH genes in mammals, with the corresponding protein products and their expression patternThe phylogenetic tree on the left is modified from that of the human MYH head domain (see McGuigan et al. 2004; Ikeda et al. 2007). Spacing and length of the branches do not reflect actual scale in this simplified scheme.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2821527&req=5

fig06: Scheme illustrating the evolutionary relationships among sarcomeric MYH genes in mammals, with the corresponding protein products and their expression patternThe phylogenetic tree on the left is modified from that of the human MYH head domain (see McGuigan et al. 2004; Ikeda et al. 2007). Spacing and length of the branches do not reflect actual scale in this simplified scheme.

Mentions: The expression analysis of the two sarcomeric MYHs, MYH14 and MYH15, reported here completes the picture of sarcomeric MYH gene expression in mammalian striated muscles (Fig. 6). We find that MYH14 gene, the orthologue of chicken slow myosin 2, is detected in both heart and slow skeletal muscles at the transcript level, but only in the slow-tonic fibres of EO muscles and in bag fibres of muscle spindles at the protein level. MYH14 is, thus, the gene coding for the mammalian slow-tonic myosin, whose existence was previously postulated based on the reactivity of anti-chicken myosin antibodies but was never demonstrated. In contrast, MYH15 gene, the orthologue of frog and chicken ventricular MYH, is expressed exclusively in a restricted region of EO muscles and in the extracapsular region of bag fibres of muscle spindles. The results of this study are of interest with respect both to MYH gene evolution in vertebrates and to the possible functional significance of these genes.


Two novel/ancient myosins in mammalian skeletal muscles: MYH14/7b and MYH15 are expressed in extraocular muscles and muscle spindles.

Rossi AC, Mammucari C, Argentini C, Reggiani C, Schiaffino S - J. Physiol. (Lond.) (2009)

Scheme illustrating the evolutionary relationships among sarcomeric MYH genes in mammals, with the corresponding protein products and their expression patternThe phylogenetic tree on the left is modified from that of the human MYH head domain (see McGuigan et al. 2004; Ikeda et al. 2007). Spacing and length of the branches do not reflect actual scale in this simplified scheme.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2821527&req=5

fig06: Scheme illustrating the evolutionary relationships among sarcomeric MYH genes in mammals, with the corresponding protein products and their expression patternThe phylogenetic tree on the left is modified from that of the human MYH head domain (see McGuigan et al. 2004; Ikeda et al. 2007). Spacing and length of the branches do not reflect actual scale in this simplified scheme.
Mentions: The expression analysis of the two sarcomeric MYHs, MYH14 and MYH15, reported here completes the picture of sarcomeric MYH gene expression in mammalian striated muscles (Fig. 6). We find that MYH14 gene, the orthologue of chicken slow myosin 2, is detected in both heart and slow skeletal muscles at the transcript level, but only in the slow-tonic fibres of EO muscles and in bag fibres of muscle spindles at the protein level. MYH14 is, thus, the gene coding for the mammalian slow-tonic myosin, whose existence was previously postulated based on the reactivity of anti-chicken myosin antibodies but was never demonstrated. In contrast, MYH15 gene, the orthologue of frog and chicken ventricular MYH, is expressed exclusively in a restricted region of EO muscles and in the extracapsular region of bag fibres of muscle spindles. The results of this study are of interest with respect both to MYH gene evolution in vertebrates and to the possible functional significance of these genes.

Bottom Line: During development, MYH14 is expressed at low levels in skeletal muscles, heart and all EO muscle fibres but disappears from most fibres, except the slow-tonic fibres, after birth.In contrast, MYH15 is absent in embryonic and fetal muscles and is first detected after birth in the orbital layer of EO muscles.The identification of the expression pattern of MYH14 and MYH15 brings to completion the inventory of the MYH isoforms involved in sarcomeric architecture of skeletal muscles and provides an unambiguous molecular basis to study the contractile properties of slow-tonic fibres in mammals.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Sciences, University of Padova, Padova, Italy.

ABSTRACT
The mammalian genome contains three ancient sarcomeric myosin heavy chain (MYH) genes, MYH14/7b, MYH15 and MYH16, in addition to the two well characterized clusters of skeletal and cardiac MYHs. MYH16 is expressed in jaw muscles of carnivores; however the expression pattern of MYH14 and MYH15 is not known. MYH14 and MYH15 orthologues are present in frogs and birds, coding for chicken slow myosin 2 and ventricular MYH, respectively, whereas only MYH14 orthologues have been detected in fish. In all species the MYH14 gene contains a microRNA, miR-499. Here we report that in rat and mouse, MYH14 and miR-499 transcripts are detected in heart, slow muscles and extraocular (EO) muscles, whereas MYH15 transcripts are detected exclusively in EO muscles. However, MYH14 protein is detected only in a minor fibre population in EO muscles, corresponding to slow-tonic fibres, and in bag fibres of muscle spindles. MYH15 protein is present in most fibres of the orbital layer of EO muscles and in the extracapsular region of bag fibres. During development, MYH14 is expressed at low levels in skeletal muscles, heart and all EO muscle fibres but disappears from most fibres, except the slow-tonic fibres, after birth. In contrast, MYH15 is absent in embryonic and fetal muscles and is first detected after birth in the orbital layer of EO muscles. The identification of the expression pattern of MYH14 and MYH15 brings to completion the inventory of the MYH isoforms involved in sarcomeric architecture of skeletal muscles and provides an unambiguous molecular basis to study the contractile properties of slow-tonic fibres in mammals.

Show MeSH
Related in: MedlinePlus