HOXD9

HOXD9 is a gene that belongs to the homeobox family of genes. The HOX genes are a group of related genes that control the body plan of an embryo along the head-tail axis. After the embryonic segments have formed, the HOX proteins determine the type of segment structures (e.g., legs, antennae, and wings in fruit flies or the different types of vertebrae in humans) that will form on a given segment. HOX proteins thus confer segmental identity, but do not form the actual segments themselves.

Function

The protein encoded by the HOXD9 gene is a DNA-binding transcription factor that may regulate gene expression, morphogenesis, and differentiation. More specifically, it may function in fertility, embryo viability, and regulation of embryonic limb identity.

Clinical Significance

Mutations in HOXD9 have been associated with several diseases, including polydactyly, a condition characterized by the presence of more than the usual number of fingers or toes, and synpolydactyly, where there is a combination of polydactyly and syndactyly (webbing or fusion of the fingers or toes).

Expression

HOXD9 is expressed in many tissues. In adults, the highest levels of expression are found in the placenta and pancreas. In the embryo, expression is found in the developing limbs, heart, and neural tube.

See Also

• Homeobox
• HOX genes
• Polydactyly
• Synpolydactyly