OVERVIEW and NOMENCLATURE

The homeotic Hox proteins are sequence-specific transcription factor which are part of a developmental regulatory system that provides cells with specific positional identities on the anterior-posterior (A-P) axis [1].The hox proteins contain an `homeobox' domain. In Drosophila and other insects there are eight different Hox genes that are encoded in two gene complexes: ANT-C and BX-C; while in vertebrates there are 38 genes organized in four complexes. Recently [2,3] a new nomenclature system has been proposed for Hox genes. The four gene complexes are assigned the letters A to D. Based on sequence similarities the genes can be sorted into 13 `paralog' groups. The order of the paralogs along the chromosomes are conserved in the four complexes. The gene name is obtained by concatenating the gene complex letter designation with the group number; examples: HOXA1, HOXB4, HOXC8, HOXD13, etc. In several cases a representative of a paralog group is absent from a complex, in such cases that gene number is omitted. For example: HOXA8, HOXC1 andHOXD2 do not exist.

[1] McGinnis W., Krumlauf R. Cell 68:283-302(1992).

[2] Scott M.P. Cell 71:551-553(1992).

[3] Scott M.P. Nucleic Acids res. 21:1687-1688(1993).