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PRD Class
Families List  Genes List
The PRD class is the second largest of the homeobox gene classes in animal genomes; like the ANTP class these genes have only been found in animals. The PRD class derives its name from (but is not an abbreviation for) the Paired (Prd) gene of Drosophila. PRD class genes are defined phylogenetically - they form a robust monophyletic group in evolutionary trees of homeodomain sequences. The PRD homeobox class overlaps with the Pax gene class - some but not all Pax genes are in the PRD homeobox gene class, while the vast majority of PRD class homeobox genes are not Pax genes.

There are 9 Pax genes in the human or mouse genomes, defined by presence of a 128 amino acid Paired domain, and of these 7 are members of the PRD homeobox class by virtue of possessing a homeobox: complete homeobox for PAX3, 4, 6 and 7; partial homeobox for PAX2, 5 and 8 (the two human Pax genes lacking a homeobox entirely are PAX1 and PAX9; these are not included in this database). In addition to these 7 homeobox-containing Pax genes, there are a further 43 PRD class genes in the human genome. These 50 genes can be divided into 31 gene families. There are also 24 human pseudogenes generated from these genes, plus an unknown number of DUX repetitive sequences (Holland et al. 2007).

In amphioxus there are 5 Pax genes, and of these 3 are have a partial or complete homeobox (Pax-1/9 and Pon are the two lacking homeobox sequence and therefore excluded; Pon is present in Drosophila and amphioxus, but not human). In addition to these genes, there are a further 27 PRD class genes in amphioxus (Takatori et al. 2008).

Holland PWH, Booth HAF, Bruford EA (2007) BMC Biology 5:47.
Takatori N et al (2008) Dev Genes Evol 218: 579-590.
Families List of Class PRD :
Loci in PRD of Chicken back to top..
ALX1ALX homeobox 1AlxChicken 
ALX4ALX homeobox 4AlxChicken 
ARXaristaless related homeoboxArxChicken 
DMBX1diencephalon/mesencephalon homeobox 1DmbxChicken 
DRGXdorsal root ganglia homeoboxDrgxChicken 
GSCgoosecoid homeoboxGscChicken 
GSC2goosecoid homeobox 2GscChicken 
HESX1HESX homeobox 1HesxChicken 
HOPXHOP homeoboxHopxChicken 
ISXintestine-specific homeoboxIsxChicken 
LOC419032similar to newborn ovary homeodomain proteinNoboxChicken 
LOC769839Mix likeMixChicken 
LOC771564Otp likeOtpChicken 
MIXL1Mix1 homeobox-like 1MixChicken 
PAX3paired box 3Pax3/7Chicken 
PAX6paired box gene 6Pax4/6Chicken 
PAX7paired box 7Pax3/7Chicken 
PHOX2Bpaired-like homeobox 2bPhoxChicken 
PITX1paired-like homeodomain 1PitxChicken 
PITX2paired-like homeodomain 2PitxChicken 
PITX3paired-like homeodomain 3PitxChicken 
PRRX1paired related homeobox 1PrrxChicken 
PRRX2paired related homeobox 2PrrxChicken 
RX2retina and anterior neural fold homeoboxRaxChicken 
SEBOXSEBOX homeoboxSeboxChicken 
SHOX2short stature homeobox 2ShoxChicken 
UNCXUNC homeoboxUncxChicken 
VSX1visual system homeobox 1VsxChicken 
VSX2visual system homeobox 2VsxChicken