The HOXA13 gene provides instructions for producing a protein that attaches (binds) to specific regions of DNA and regulates the activity of other genes. On the basis of this role, the HOXA13 gene is called a transcription factor. The HOXA13 gene is part of a larger family of transcription factors called homeobox genes, which act during early embryonic development to control the formation of many body structures. Specifically, the HOXA13 protein appears to be critical for the formation and development of the limbs (particularly the hands and feet), urinary tract, and reproductive system.
The HOXA13 gene contains three areas where a protein building block (amino acid) called alanine is repeated multiple times. These stretches of alanines are known as polyalanine tracts or poly(A) tracts. The role of polyalanine tracts in normal HOXA13 function is unknown.
At least 14 mutations in the HOXA13 gene have been found to cause hand-foot-genital syndrome. More than half of these mutations affect one of the polyalanine tracts in the HOXA13 gene. These mutations add extra alanines to these tracts, making them abnormally long and unstable. The resulting altered protein is degraded by the cell, so it is unavailable to regulate the activity of other genes during early development. These changes affect the development of the hands, feet, urinary tract, and reproductive system.
Other HOXA13 mutations result in the production of an abnormally short, nonfunctional version of the HOXA13 protein or change single amino acids in the protein. Mutations that substitute one amino acid for another amino acid may change the way the HOXA13 protein is folded. The altered protein may or may not function or bind to DNA normally. Mutations that result in an altered but functional HOXA13 protein may cause more severe signs and symptoms of hand-foot-genital syndrome than mutations that lead to a nonfunctional version of this protein.
Chromosomal rearrangements (translocations) involving the short (p) arm of chromosome 7 have been associated with rare cases of leukemia, a cancer of blood-forming cells. These translocations disrupt the region of chromosome 7 that contains several similar homeobox genes, including HOXA13.
Within cancer cells, researchers have found translocations between chromosome 7 and chromosome 11 in several people with leukemia. These rearrangements abnormally fuse part of HOXA13 or a similar gene on chromosome 7 to part of the NUP98 gene on chromosome 11. The protein produced from the fused gene probably signals abnormal cells to continue dividing without control or order, which likely contributes to the development of cancer.
homeo box 1J
homeo box A13
Homeobox protein Hox-A13
homeobox protein HOXA13
transcription factor HOXA13