Semaphorin 6C expression in innervated and denervated skeletal muscle
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Semaphorins are secreted or transmembrane proteins important for axonal guidance and for the structuring of neuronal systems. Semaphorin 6C, a transmembrane Semaphorin, has growth cone collapsing activity and is expressed in adult skeletal muscle. In the present study the expression of Semaphorin 6C mRNA and immunoreactivity has been compared in innervated and denervated mouse hind-limb and hemidiaphragm muscles. Microscopic localization of immunoreactivity was studied in innervated and denervated rat skeletal muscle. The results show that Semaphorin 6C mRNA expression and immunoreactivity on Western blots are down-regulated following denervation. The mRNA of Semaphorin 6C as well as immunoreactivity determined by Western blots are expressed in extrasynaptic as well as perisynaptic regions of muscle. Immunohistochemical studies, however, show Semaphorin 6C-like immunoreactivity to be concentrated at neuromuscular junctions. The results suggest a role for Semaphorin 6C in neuromuscular communication.
KeywordsSemaphorin 6C Skeletal muscle Denervation Neuromuscular junction Endplate
We are grateful to Dr. Lennart Mellblom and Anita Jäderberg for providing access to cryostats at the County Hospital in Kalmar and to Dr. Caroline Magnusson for cloning the β-actin cDNA fragment. This work was supported by grants from the Faculty of Natural Sciences and Technology, University of Kalmar, the Crafoord Foundation, the Knowledge Foundation (KK-stiftelsen) and from Umeå University Hospital, Clinical Neuroscience Research Fund, Sweden.
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