HOX HOMEOBOX GENES AND REGIONALIZATION OF THE NERVOUS-SYSTEM

The Hox family of homeobox-containing genes are intimately associated with the processes of axial patterning in vertebrate embryos. This fam ily of transcription factors is widely conserved in evolution and by a nalogy with their Drosophila counterparts, the HOM-C homeotic genes, m ay play a role in establishing regional identity in a number of embryo nic systems, including the CNS. The patterns of expression of these ge nes are linked with the generation of rhombomeres and neural crest in the developing hindbrain, and suggest that they provide a molecular sy stem for generating a combinatorial patterning mechanism. Analysis of mouse Hox mutants generated by homologous recombination have clearly d emonstrated that the genes have important roles in normal regionalisat ion of the hindbrain and branchial arches, and this has lead to intere st in how their early patterns are established in the nervous system. The Hox genes and their relation to hindbrain segmentation therefore p rovide a means of examining the cascade of events which regulates patt ern formation in early neural development. (C) 1993 John Wiley & Sons, Inc.