ALPHA(V) INTEGRIN SUBUNIT IS PREDOMINANTLY LOCATED IN NERVOUS-TISSUE AND SKELETAL-MUSCLE DURING MOUSE DEVELOPMENT

alpha(v) integrin subunit can dimerize with different beta subunits to form receptors for several matrix proteins. The function of these rec eptors in vivo is still largely unknown. We examined the localization of alpha(v) integrin during mouse development and showed that its dist ribution is dynamically regulated in the glia of the central nervous s ystem and in skeletal muscle. Immunoreactivity in the neural tube was firstly localized at embryonic day 10.5 (E10.5) around cell bodies lin ing the lumen and along tiny fibres extending towards the outer margin . At E12.5 alpha(v) distribution follows the highly defined pattern of the radial glia: fascicles of immunoreactive fibres form parallel pal isades, in particular along the hindbrain and the spinal cord. At E15. 5, although with weaker intensity, alpha(v) was still detectable in ra dial glia fibres, and it codistributed with glial fibrillary acidic pr otein positive fascicles. After birth (P8) alpha(v) immunoreactivity i n the brain and spinal cord decreased dramatically, but remained high in the radial glia of the cerebellum. In adult mice alpha(v) reactivit y in the central nervous system disappeared. During myogenesis or, app ears at E10.5 in myotomal cells and from E12.5 alpha(v) was evident in myoblasts and in myotubes. In the developing skeletal muscle of E15.5 embryos, immunoreactivity became more concentrated in the apical port ion of the myotubes. In adult striated muscle the amount of or, subuni t dramatically declined and immunostaining was no longer detectable. D uring development, alpha(v) was weakly evident in other sites ineludin g heart and endothelia of blood vessels, mesonephric tubula, smooth mu scle of the digestive tract, and bronchia. Comparative analysis of the localization of alpha(v), alpha(3), and alpha(5) integrin subunits in dicated that alpha(v) has a unique and highly regulated distribution p attern. The distribution in the nervous system is consistent with a ro le of alpha(v) in neuron-glia interaction during the organization of t he neuronal layers in the brain cortex and in the cerebellum. Moreover , alpha(v) is likely to be involved in the myotendinous junction durin g embryonic life, suggesting a dual functional role of this integrin i n muscle and nervous tissue. (C) 1994 Wiley-Liss, Inc.