TENASCIN-C MESSENGER-RNA IS EXPRESSED IN CRANIAL NEURAL CREST CELLS, IN SOME PLACODAL DERIVATIVES, AND IN DISCRETE DOMAINS OF THE EMBRYONICZEBRAFISH BRAIN

A partial zebrafish tenascin-C cDNA clone was isolated from an embryon ic zebrafish cDNA library on the basis of homology to mouse tenascin-C . The expression pattern in the head of embryonic zebrafish was analyz ed by in situ hybridization. Tenascin-C mRNA was detected in neural cr est cells during the period of their migration and differentiation. Ex pression also occurred in differentiating placodal tissues and in meso dermal cells. In the developing brain, tenascin-C mRNA was expressed i n specific domains. In the hindbrain the pattern of the domains was dy namic. At 18 to 22 h postfertilization, expression was widespread in r hombomeres 3, 5, and 6, confined to periventricular cells in rhombomer e 2, and not detectable in rhombomere 4. At 32 h postfertilization, te nascin-C was expressed at the rhombomere boundaries. In contrast to th e hindbrain, the pattern in the forebrain and midbrain did not show an y major changes between 22 and 32 h postfertilization. Domains express ing tenascin-C alternated with regions devoid of it. The most anterior domain of expression was observed at the telencephalic-diencephalic b order, surrounding the optic recess. A second domain, at the border be tween the diencephalon and the midbrain, and a third domain, in the ca udal midbrain tegmentum, appeared restricted to the basal plate. Addit ionally, expression of tenascin-C mRNA was detected in the hypothalamu s and in the developing epiphysis. These expression patterns suggest t hat tenascin-C may play a role in neural crest cell migration and duri ng the differentiation of neural crest, placodal, and mesodermal deriv atives. In the developing brain, tenascin-C may be involved in the con solidation of different regional identities. (C) 1995 John Wiley & Son s, Inc.