BRANCHIAL HOX GENE-EXPRESSION AND HUMAN CRANIOFACIAL DEVELOPMENT

Members of the Antennapedia class of homeobox genes, known as Hox gene s, are believed to be pivotal in vertebrate craniofacial development. Here we show that eight members of paralogous groups 1, 2, 3, and 4 ar e expressed in the human embryonic hindbrain and branchial arches at 4 weeks of development. The combinatorial patterns of expression of gen es representing the first three paralogous groups parallel the pattern s described for their homologues in various animal models, demonstrati ng a high degree of conservation of the branchial Hox code. Arch expre ssion of group 4 genes is defined for the first time in any vertebrate . Furthermore, as development proceeds, individual paralogues of a sin gle paralogous group (group 3), which initially share a common express ion domain, are differentially down-regulated in a tissue-, organ-, or site-specific fashion. (C) 1997 Academic Press.