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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.

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Syntenic organization of MYH14/7b and MYH15 genes and amino acid sequence of MYH14 and MYH15 loops 1 and 2A, physical maps showing syntenic organization of MYH14/7b and MYH15 genes in fish, frog, chicken and mammals. The microRNA, miR-499, is contained within the MYH14 gene in all species. Spacing of markers does not reflect actual scale. Gene organization information was obtained by NCBI and Ensembl Genome Browser databases (see Table S1 for gene ID). B, amino acid sequence of MYH14 and MYH15 loop 1 and loop 2 in different vertebrate species. The structure of the two surface loops in other human sarcomeric MYHs is also shown for comparison. The dog sequence is shown for MYH16, because human MYH16 is a pseudogene.
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fig01: Syntenic organization of MYH14/7b and MYH15 genes and amino acid sequence of MYH14 and MYH15 loops 1 and 2A, physical maps showing syntenic organization of MYH14/7b and MYH15 genes in fish, frog, chicken and mammals. The microRNA, miR-499, is contained within the MYH14 gene in all species. Spacing of markers does not reflect actual scale. Gene organization information was obtained by NCBI and Ensembl Genome Browser databases (see Table S1 for gene ID). B, amino acid sequence of MYH14 and MYH15 loop 1 and loop 2 in different vertebrate species. The structure of the two surface loops in other human sarcomeric MYHs is also shown for comparison. The dog sequence is shown for MYH16, because human MYH16 is a pseudogene.

Mentions: Nucleotide sequences were identified and amino acid sequences were deduced using public databases and tools (see online Supplemental Material, Table S1). Sequences were aligned using the BLAST program available at NCBI. Physical maps were created using NCBI databases to obtain the syntenies reported in Fig. 1. However, the Ensembl genome browser (http://www.ensembl.org/) and JGI database (http://genome.jgi-psf.org/Xentr4/Xentr4.home.html) were used to determine the gene order of Xenopus tropicalis MYH genes. Some MYH genes, for example rat Myh15, are not identified as such in public databases. In this case, known genes located upstream and downstream of MYH15 in the human genome were identified in the rat genome and genes in between were aligned to known putative orthologues using NCBI BLAST. Rat Myh15 was found to correspond to a gene called RGD1565858 (see Table S1). A similar approach was also used for other Myh14 and Myh15 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)

Syntenic organization of MYH14/7b and MYH15 genes and amino acid sequence of MYH14 and MYH15 loops 1 and 2A, physical maps showing syntenic organization of MYH14/7b and MYH15 genes in fish, frog, chicken and mammals. The microRNA, miR-499, is contained within the MYH14 gene in all species. Spacing of markers does not reflect actual scale. Gene organization information was obtained by NCBI and Ensembl Genome Browser databases (see Table S1 for gene ID). B, amino acid sequence of MYH14 and MYH15 loop 1 and loop 2 in different vertebrate species. The structure of the two surface loops in other human sarcomeric MYHs is also shown for comparison. The dog sequence is shown for MYH16, because human MYH16 is a pseudogene.
© Copyright Policy
Related In: Results  -  Collection

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

fig01: Syntenic organization of MYH14/7b and MYH15 genes and amino acid sequence of MYH14 and MYH15 loops 1 and 2A, physical maps showing syntenic organization of MYH14/7b and MYH15 genes in fish, frog, chicken and mammals. The microRNA, miR-499, is contained within the MYH14 gene in all species. Spacing of markers does not reflect actual scale. Gene organization information was obtained by NCBI and Ensembl Genome Browser databases (see Table S1 for gene ID). B, amino acid sequence of MYH14 and MYH15 loop 1 and loop 2 in different vertebrate species. The structure of the two surface loops in other human sarcomeric MYHs is also shown for comparison. The dog sequence is shown for MYH16, because human MYH16 is a pseudogene.
Mentions: Nucleotide sequences were identified and amino acid sequences were deduced using public databases and tools (see online Supplemental Material, Table S1). Sequences were aligned using the BLAST program available at NCBI. Physical maps were created using NCBI databases to obtain the syntenies reported in Fig. 1. However, the Ensembl genome browser (http://www.ensembl.org/) and JGI database (http://genome.jgi-psf.org/Xentr4/Xentr4.home.html) were used to determine the gene order of Xenopus tropicalis MYH genes. Some MYH genes, for example rat Myh15, are not identified as such in public databases. In this case, known genes located upstream and downstream of MYH15 in the human genome were identified in the rat genome and genes in between were aligned to known putative orthologues using NCBI BLAST. Rat Myh15 was found to correspond to a gene called RGD1565858 (see Table S1). A similar approach was also used for other Myh14 and Myh15 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