Gene: [HOXD/02q31] homeo box region D, gene cluster on chr 2q31; (HOXD1 HOXD3 HOXD4 HOXD8 HOXD9 HOXD10 HOXD11 HOXD12 HOXD13)

FUN

 The patterns of HOXD gene expression divide the embryonic limb bud into 5 sectors along the anterior/posterior axis. The expression of specific HOX genes in each domain specifies the developmental fate of that region. Because there are only 5 distinct HOX-encoded domains across the limb bud, there is a developmental constraint prohibiting the evolution of more than 5 different types of digits. The expression of the HOX4.4 to HOX4.8 genes (GEM:02q31/HOXD10, GEM:02q31/HOXD8, GEM:02q31/HOXD11, GEM:02q31/HOXD1, GEM:02q31/HOXD12) is akin to a nested set, like Russian dolls, with all of the genes being expressed at the same posterior border and each gene's expression extending to a successively more anterior position. They are also expressed in a temporal order such that the HOX4.4 gene (GEM:02q31/HOXD10) is the first to be expressed. Subsequently, HOX4.5 (GEM:02q31/HOXD8) is activated, and so on. Each is initially expressed just at the posterior margin and then spreads anteriorly (Tabin-1992)."

PAT

 Polydactyly/Asyndactyly might be the consequence of mutation, e.g., duplication of one of the HOX4/HOXD genes (see GEM:02q31/HOXD13). However, the HOX4/HOXD genes are also coordinately expressed in the CNS and elsewhere in the body mesenchyme. Thus, altering their expression would affect more than just the limb. In theory, the effects of a newly derived HOX4 gene could be limited to the limbs by creating a limb-specific promoter."

FAG

 [1] A precise number of human HOX genes is currently unknown. Up to the present, four HOX gene clusters have been mapped: HOXD in chromosome 2q31 (FAM:HOXD/02q31), HOXA in chromosome 7p1 (FAM:HOXA/07p1), HOXC in chromosome 12q1 (FAM:HOXC/12q1), and HOXB in chromosome 17q2 (GEM:17q2/HOXB5; GEM:17q2/HOXB6; GEM:17q2/HOXB7).
[2] The following single genes were also mapped: MSX1 (GEM:04p161/MSX1), CHX10, HOX11, EVX1, and EVX2 (see FAM:HOX/00.0)."

REL

 FAM:COLL/00.0

REF

 LOC,MOL,REV "Acampora D &: NAR, 17, 10385-10402, 1989
LOC,MOL,REV "Cannizzaro LA &: AJHG, 41, 1-15, 1987
NOM "McAlpine PJ, Shows: Genomics, 7, 460, 1990