EVIDENCE FOR A MITOGENIC EFFECT OF WNT-1 IN THE DEVELOPING MAMMALIAN CENTRAL-NERVOUS-SYSTEM

The analysis of mutant alleles at the Wnt-1 locus has demonstrated tha t Wnt-1-mediated cell signalling plays a critical role in development of distinct regions of the embryonic central nervous system (CNS). To determine how these signals participate in the formation of the CNS, w e have ectopically expressed this factor in the spinal cord under the control of the Hoxb-4 Region A enhancer. Ectopic Wnt-1 expression caus es a dramatic increase in the number of cells undergoing mitosis in th e ventricular region and a concomitant ventricular expansion. Although this leads to consistent changes in the relative proportions of dorsa l and ventral regions, Wnt-1 does not appear to act as a primary patte rning signal. Rather, our experiments indicate that Wnt-1 can act as a mitogen in the developing CNS.