HTT gene
The HTT gene provides instructions for making the protein huntingtin, which is essential for normal brain development and nerve cell function.
Normal Function
The HTT gene provides instructions for making a protein called huntingtin. While its exact function is unknown, it is essential for normal development before birth and plays an important role in neurons. Within cells, huntingtin is involved in chemical signaling, transporting materials, binding to other proteins, and protecting cells from self-destruction (apoptosis). It may also play a role in repairing damaged DNA.
The HTT gene contains a segment known as a CAG trinucleotide repeat, which consists of the DNA building blocks cytosine, adenine, and guanine repeated multiple times. In healthy individuals, this segment is repeated 10 to 35 times.
Health Conditions Related to Genetic Changes
Huntington's disease
Huntington's disease is caused by a CAG trinucleotide repeat expansion, where the segment is repeated 36 to more than 120 times. People with 40 or more repeats almost always develop the disorder.
This expansion leads to the production of an abnormally long version of the huntingtin protein. This protein is cut into smaller, toxic fragments that accumulate in neurons, disrupting their function. The loss of the protein's DNA repair function may also lead to the accumulation of DNA damage in neurons over time. The disease particularly affects the striatum and cerebral cortex, regions of the brain that coordinate movement and control emotions and thinking.
The condition often exhibits anticipation, where the repeat size increases as the gene is passed to the next generation, typically resulting in an earlier onset of symptoms. Individuals with 27 to 35 repeats do not develop the disease themselves but are at risk of having children who will.
Other Names for This Gene
- HD
- HD_HUMAN
- huntingtin (Huntington disease)
- Huntington's disease protein
- IT15