Cdx

The Cdx gene family, also called caudal genes, are a group of genes found in many animal genomes. Cdx genes contain a homeobox DNA sequence and code for proteins that act as transcription factors. The gene after which the gene family is named (the founding member) is the caudal or cad gene of the fruitfly Drosophila melanogaster. The human genome has three Cdx genes, called CDX1, CDX2 and CDX4. The zebrafish has no cdx2 gene, but two copies of cdx1 and one copy of cdx4. The Cdx gene in the nematode Caenorhabditis elegans is called pal-1.

Cdx genes play many roles during embryological development. This is particularly seen during the development of the body plan. Cdx genes are transcription factors that are influenced by signaling molecules such as Wnt during body plan establishment in the developing embryo. Expression of Cdx is responsible for the control of the Hox gene family, which establishes the body plan posteriorly and anteriorly. Transfer of this information to Hox genes for positional development works directly through Cdx binding sites. Mutations to these binding sites have shown to ultimately prevent Hox gene expression and affect proper establishment of the body plan by preventing regulation of region-specific expression.

Research demonstrating decreases in Cdx dosage within mice has shown defects in anterior and posterior axis development. This has shown more severe vertebral defects posteriorly as Cdx dosage decreases. Along with this, it has been found that as Cdx dosage decreases, modification of Wnt signaling, and timing of Hox expression causes both neurological and skeletal defects in the posterior vertebra.

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