The DUX4 gene is located near the end of chromosome 4 in a region known as D4Z4. This region consists of 11 to more than 100 repeated segments, each of which is about 3,300 DNA base pairs (3.3 kb) long. The entire D4Z4 region is normally hypermethylated, which means that it has a large number of methyl groups (consisting of one carbon atom and three hydrogen atoms) attached to the DNA. The addition of methyl groups turns off (silences) genes, so hypermethylated regions of DNA tend to have fewer genes that are turned on (active).
Each of the repeated segments in the D4Z4 region contains a copy of the DUX4 gene; the copy closest to the end of chromosome 4 is called DUX4, while the other copies are described as “DUX4-like” or DUX4L. Hypermethylation of the D4Z4 region keeps the DUX4-like genes silenced all the time. No protein is produced from these genes. The DUX4 gene is also silenced in most adult cells and tissues, although it is active during early development and in the testes of adult males. Little is known about the function of the protein produced from the active DUX4 gene; it appears to help control the activity of other genes.
The DUX4 gene (the copy closest to the end of chromosome 4) is located next to a regulatory region of DNA known as a pLAM sequence, which is necessary for the production of the DUX4 protein. Some copies of chromosome 4 have a functional pLAM sequence, while others do not. Copies of chromosome 4 with a functional pLAM sequence are described as 4qA or “permissive.” Those without a functional pLAM sequence are described as 4qB or “non-permissive.” Without a functional pLAM sequence, no DUX4 protein is made. Because there are two copies of chromosome 4 in each cell, individuals may have two “permissive” copies of chromosome 4, two “non-permissive” copies, or one of each.
Other Names
double homeobox 4-like; double homeobox protein 10; double homeobox protein 4; double homeobox protein 4/10
Related Genetics Topics
Identifiers
- NCBI Gene: 100288687
- OMIM: 606009
Source: MedlinePlus Genetics, U.S. National Library of Medicine.
