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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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Quantitative RT-PCR analysis of different rat striated muscles with probes specific for MYH14 and MYH15 gene transcriptsThe expression pattern of MYH7, coding for β/slow MYH, is shown for comparison. Transcripts levels are normalized to housekeeping genes and expressed as the percentage of the tissue with the highest expression level. Note that the distribution of miR-499 is similar to that of MYH14. EO: extraocular muscles; SOL: slow-twitch soleus muscle; TA: fast-twitch tibialis anterior muscle. Data are means ±s.e.m.; n= 6 (MYH14 and MYH15), n= 3 (MYH7 and mir-499).
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fig02: Quantitative RT-PCR analysis of different rat striated muscles with probes specific for MYH14 and MYH15 gene transcriptsThe expression pattern of MYH7, coding for β/slow MYH, is shown for comparison. Transcripts levels are normalized to housekeeping genes and expressed as the percentage of the tissue with the highest expression level. Note that the distribution of miR-499 is similar to that of MYH14. EO: extraocular muscles; SOL: slow-twitch soleus muscle; TA: fast-twitch tibialis anterior muscle. Data are means ±s.e.m.; n= 6 (MYH14 and MYH15), n= 3 (MYH7 and mir-499).

Mentions: Quantitative RT-PCR analysis was used to examine the expression pattern of MYH14 and MYH15 in mammalian muscles. MYH14 and miR-499 transcripts are present in rat heart, slow skeletal muscles and EO muscles but only at low levels in fast skeletal muscles (Fig. 2). In contrast, MYH15 transcripts are present at high levels in EO muscles but absent in fast and slow leg muscles and heart. The pattern of distribution of these MYH transcripts is similar in mouse muscles (Fig. S2A) and is completely different from that of typical slow and fast MYH, such as the MYH7 gene, coding for MYH-β/slow, expressed in slow-twitch fibres, and MYH4 gene, expressed in MYH-2B fibres. In human skeletal muscle MYH14 transcripts are present in EO muscles but also in vastus lateralis and in both atrial and ventricular myocardium, whereas MYH15 transcripts are detectable exclusively in EO muscles with minimal traces in myocardial tissues (Fig. S2B).


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)

Quantitative RT-PCR analysis of different rat striated muscles with probes specific for MYH14 and MYH15 gene transcriptsThe expression pattern of MYH7, coding for β/slow MYH, is shown for comparison. Transcripts levels are normalized to housekeeping genes and expressed as the percentage of the tissue with the highest expression level. Note that the distribution of miR-499 is similar to that of MYH14. EO: extraocular muscles; SOL: slow-twitch soleus muscle; TA: fast-twitch tibialis anterior muscle. Data are means ±s.e.m.; n= 6 (MYH14 and MYH15), n= 3 (MYH7 and mir-499).
© Copyright Policy
Related In: Results  -  Collection

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

fig02: Quantitative RT-PCR analysis of different rat striated muscles with probes specific for MYH14 and MYH15 gene transcriptsThe expression pattern of MYH7, coding for β/slow MYH, is shown for comparison. Transcripts levels are normalized to housekeeping genes and expressed as the percentage of the tissue with the highest expression level. Note that the distribution of miR-499 is similar to that of MYH14. EO: extraocular muscles; SOL: slow-twitch soleus muscle; TA: fast-twitch tibialis anterior muscle. Data are means ±s.e.m.; n= 6 (MYH14 and MYH15), n= 3 (MYH7 and mir-499).
Mentions: Quantitative RT-PCR analysis was used to examine the expression pattern of MYH14 and MYH15 in mammalian muscles. MYH14 and miR-499 transcripts are present in rat heart, slow skeletal muscles and EO muscles but only at low levels in fast skeletal muscles (Fig. 2). In contrast, MYH15 transcripts are present at high levels in EO muscles but absent in fast and slow leg muscles and heart. The pattern of distribution of these MYH transcripts is similar in mouse muscles (Fig. S2A) and is completely different from that of typical slow and fast MYH, such as the MYH7 gene, coding for MYH-β/slow, expressed in slow-twitch fibres, and MYH4 gene, expressed in MYH-2B fibres. In human skeletal muscle MYH14 transcripts are present in EO muscles but also in vastus lateralis and in both atrial and ventricular myocardium, whereas MYH15 transcripts are detectable exclusively in EO muscles with minimal traces in myocardial tissues (Fig. S2B).

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