Why adult mammalian intrafusal and extrafusal fibers contain different myosin heavy-chain isoforms

Multiple isoforms of the contractile protein myosin are present in mammalian skeletal muscles. The diversity of the heavy-chain subunits of myosin (MyHCs) in intrafusal fibers is thought to reflect a pathway of differentiation that is unique to muscle spindles. In fact, intrafusal MyHCs are developm...

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Bibliographic Details
Published in:Trends in Neurosciences 1999-04, Vol.22 (4), p.180-184
Main Authors: Walro, Jon M, Kucera, Jan
Format: Article
Language:English
Subjects:
Afferent neurons
Afferent Pathways - physiology
Aging - metabolism
Animals
Biological and medical sciences
Cell Lineage
Efferent neurons
Fetal Proteins - metabolism
Fundamental and applied biological sciences. Psychology
Gene Expression Regulation, Developmental
Intrafusal fibres
Mammals - anatomy & histology
Mammals - metabolism
Mice
Mice, Knockout
Mice, Transgenic
Morphogenesis
Muscle Contraction
Muscle Development
Muscle Fibers, Skeletal - chemistry
Muscle Fibers, Skeletal - classification
Muscle Proteins - deficiency
Muscle Proteins - physiology
Muscle spindles
Muscle Spindles - physiology
Muscle, Skeletal - chemistry
Muscle, Skeletal - embryology
Muscle, Skeletal - growth & development
Muscle, Skeletal - ultrastructure
Myosin
Myosin Heavy Chains - metabolism
Nerve Tissue Proteins - deficiency
Nerve Tissue Proteins - physiology
Proprioception
Protein Isoforms - metabolism
Rats
Somesthesis and somesthetic pathways (proprioception, exteroception, nociception)
interoception
electrolocation. Sensory receptors
Vertebrates: nervous system and sense organs
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Summary:Multiple isoforms of the contractile protein myosin are present in mammalian skeletal muscles. The diversity of the heavy-chain subunits of myosin (MyHCs) in intrafusal fibers is thought to reflect a pathway of differentiation that is unique to muscle spindles. In fact, intrafusal MyHCs are developmental isoforms expressed by the prenatal precursors of both intrafusal and extrafusal fibers. In adult limbs, developmental MyHCs persist in intrafusal, but not extrafusal fibers principally due to the afferent neurons that arrest their maturational replacement by MyHCs associated with faster shortening velocities. The slow shortening velocities that are characteristic of developmental MyHCs might be adaptive for precise calibration of muscle spindles as sense organs.
ISSN:0166-2236
1878-108X
DOI:10.1016/S0166-2236(98)01339-3