THE EXTRACELLULAR-MATRIX MOLECULE JANUSIN REGULATES NEURONAL MORPHOLOGY IN A SUBSTRATE AND CULTURE TIME-DEPENDENT MANNER

Janusin is an extracellular matrix glycoprotein with structural homolo gy to tenascin. In search of extracellular matrix components which gov ern the differentiation of neurons in the central nervous system, we h ave investigated the influence of janusin on the differentiation of hi ppocampal neurons in vitro. Janusin coated onto nitrocellulose was a g oad substrate for attachment of cell bodies and neurite outgrowth afte r 21 h of culture. Most cells exhibited a polarized morphology with on e long major neurite and one or two short minor neurites. When janusin was coated onto a polyornithine-conditioned plastic surface, it incre ased the polarity of neurons in that the length of major neurites was increased and the length and number of minor neurites were decreased w hen compared with the control polyornithine-conditioned plastic withou t janusin. As we have shown before for tenascin, laminin and fibronect in, polarization was preceded by an increase in the number and length of all neurites during the first hours after cell plating. This study therefore adds janusin to the increasing number of extracellular matri x glycoproteins which promote axonal but not dendritic growth.