N-CADHERIN PROTEIN DISTRIBUTION IN NORMAL EMBRYOS AND IN EMBRYOS CARRYING MUTATIONS IN THE HOMEOBOX GENE HOXA-4

N-cadherin is a calcium-dependent adhesion molecule with a potential r ole in a variety of morphogenetic events. Although a dynamic pattern o f expression in the mouse embryo has been suggested by in situ hybridi zation analysis, to date there has been no report of N-cadherin protei n expression. In this immunohistochemical study we surveyed N-cadherin protein expression in the mid-late gestation mouse embryo utilizing a recently characterized monoclonal antibody. We found N-cadherin expre ssion in a wide array of tissues, including the brain, the eye, variou s cranial ganglia, the spinal cord, spinal ganglia, somites, vertebral and limb cartilage and perichondria, the developing lung and kidney, the enteric nervous system, and germ cells. These results suggest that N-cadherin protein expression, as in the chick embryo, correlates wit h the segregation of cells and with organogenesis. As cadherins have b een proposed as targets of vertebrate Hox genes, we also examined N-ca dherin expression in two lines of Hoxa-4 mutant mice. We did not obser ve any alterations in N-cadherin expression in either Hoxa-4 null embr yos or in transgenic embryos that overexpress Hoxa-4 in the mesenchyme of the gut. However, the partial overlap in expression between Hox ge nes and N-cadherin, and the likelihood of redundancy in the regulation of target genes, leaves open the possibility that cadherins are direc t or indirect targets of Hox genes during mouse embryogenesis.