Denervated skeletal muscle displays discoordinate regulation for the synthesis of several myofibrillar proteins.

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Abstract
Synthesis patterns of myosin H and L chain isoforms, tropomyosin and troponin, were studied in chicken fast muscle denervated at both neonatal and adult stages. Denervated neonatal muscle does not synthesize the adult myosin H chain isoform at the time of denervation, but it does synthesize the adult isoform several months after denervation. Innervation does not appear to be necessary for the normal sequential replacement of embryonic and neonatal myosin H chain by the adult variant. Nerve is required, however, for the regulation of tropomyosin and troponin expression. Normally the pectoralis major muscle represses synthesis of both .beta.-tropomyosin and leg-type troponin T during late embryonic development. After denervation, however, the muscle relaxes its ongoing repression of these proteins, and significant amounts of both .beta.-tropomyosin and leg-type troponin T are synthesized by the muscle. Denervation also results in an altered pattern of myosin L chain synthesis so that the ratio of fast L chain 3/fast L chain 1 decreases. Similar results are found in muscle denervated at the adult stage. In denervated muscle, synthesis of these myofibrillar proteins is not coordinated: ongoing isoform shifts proceed to express an adult pattern of myosin H chain while tropomyosin, troponin and myosin L chain patterns appear to revert to embryonic configurations.

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