Sometimes a genetic mutation will cause an irregular protein to form, which can lead to significant health problems. One such disorder, known as Huntington's disease, results in the death of brain cells that control movement throughout the body. Huntington's disease is a progressive neurological condition that has no known cure.
Huntingtin Protein
Huntington's disease is the result of a genetic mutation in a protein called huntingtin, the National Human Genome Research Institute explains. The gene for this protein is located on the fourth chromosome of the human genome, and its function is unknown. The mutation that causes Huntington's disease affects a region of DNA that has a short repeat of three nucleotides, which are the backbone of DNA and form genes. Normally, the gene that encodes huntingtin has between 10 and 35 copies of this repeat. However, if more than 40 copies of this segment are present continuously in the huntingtin gene, it will result in the formation of an abnormal protein that causes Huntington's disease.
Mechanism
Patients who have Huntington's disease have abnormal clumps of protein formed in cells throughout the body, according to the National Institutes of Health. However, this abnormal protein only kills cells in the brain that are required for controlling movement, known as the corpus striatum. Researchers have discovered that cells in this part of the body have a protein called Rhes, which is not found anywhere else in the body. Rhes binds to the disease-causing forms of huntingtin and chemically modifies the huntingtin clumps. This process appears to make the protein toxic to cells, although researchers do not understand how the modified huntingtin protein kills brain cells.
Inheritance
The genetic mutation that causes Huntington's disease is an autosomal dominant mutation, the Genetics Home Reference notes. This means that a patient only needs to have one mutated copy of the gene to get Huntington's, and it can affect both males and females. In almost all cases, people who have Huntington's also have a parent who had the disease. However, because the disease affects people around age 40, an affected parent may not have any signs of the disease when conceiving. As the gene that codes for the huntingtin protein is passed from generation to generation, the number of the nucleotide repeats can increase. More copies of the repeated DNA sequence are associated with the disease striking earlier in life.
