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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 Nematode back to top..
alr-1AristaLess (Drosophila homeodomain) Related 1ArxNematode 
ceh-10C. Elegans Homeobox 10VsxNematode 
ceh-17C. Elegans Homeobox 17PhoxNematode 
ceh-36C. Elegans Homeobox 36OtxNematode 
ceh-37C. Elegans Homeobox 37OtxNematode 
ceh-45C. Elegans Homeobox 45GscNematode 
ceh-53C. Elegans Homeobox 53Pax3/7Nematode 
ceh-8C. Elegans Homeobox 8RaxNematode 
dsc-1Defecation Suppressor of Clk-1VsxNematode 
eyg-1EYG (Drosophila eyegone) homolog 1Pax3/7Nematode 
pax-3PAX (Paired box) transcription factor 3Pax3/7Nematode 
T13C5.4 PhoxNematode 
ttx-1abnormal ThermoTaXis 1OtxNematode 
unc-30UNCoordinated 30PitxNematode 
unc-4UNCoordinated 4UncxNematode 
unc-42UNCoordinated 42PropNematode 
vab-3Variable ABnormal morphology 3Pax4/6Nematode