αv Integrin subunit is predominantly located in nervous tissue and skeletal muscle during mouse development

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Abstract
αv integrin subunit can dimerize with different β subunits to form receptors for several matrix proteins. The function of these receptors in vivo is still largely unknown. We examined the localization of αv integrin during mouse development and showed that its distribution is dynamically regulated in the glia of the central nervous system and in skeletal muscle. Immunoreactivity in the neural tube was firstly localized at embryonic day 10.5 (E10.5) around cell bodies lining the lumen and along tiny fibers extending towards the outer margin. At E12.5 αv distribution follows the highly defined pattern of the radial glia: fascicles of immunoreactive fibres form parallel palisades, in particular along the hindbrain and the spinal cord. At E15.5, although with weaker intensity, αv was still detectable in radial glia fibres, and it codistributed with glial fibrillary acidic protein positive fascicles. After birth (P8) αv immunoreactivity in the brain and spinal cord decreased dramatically, but remained high in the radial glia of the cerebellum. In adult mice αv reactivity in the central nervous system disappeared. During myogenesis αv appears at E10.5 in myotomal cells and from E12.5 αv was evident in myoblasts and in myotubes. In the developing skeletal muscle of E15.5 embryos, immunoreactivity became more concentrated in the apical portion of the myotubes. In adult striated muscle the amount of αv subunit dramatically declined and immunostaining was no longer detectable. During development, αv was weakly evident in other sites including heart and endothelia of blood vessels, mesonephric tubula, smooth muscle of the digestive tract, and bronchia. Comparative analysis of the localization of αv, α3, and α5 integrin subunits indicated that αv has a unique and highly regulated distribution pattern. The distribution in the nervous system is consistent with a role of αv in neuron‐glia interaction during the organization of the neuronal layers in the brain cortex and in the cerebellum. Moreover, αv is likely to be involved in the myotendinous junction during embryonic life, suggesting a dual functional role of this integrin in muscle and nervous tissue.