Huntington’s Disease
Huntington’s Disease (HD) is a fatal genetic disease which causes nerve cells in the basal
ganglia and other regions of the brain to deteriorate and die. Symptoms of HD begin to appear
around 30 to 50 years of age and continue to intensify over the next 10 to 25 years after they first
surface. Symptoms of HD include changes in personality, mood swings, depression,
forgetfulness, impaired judgement, unsteady walking, chorea, slurred speech, difficulty
swallowing, and severe weight loss. The cause of death in patients with HD is not Huntington’s
Disease itself, but the complications that the symptoms of HD cause in patients (most notably
pneumonia and heart disease) that end up killing the patient. Treatments for Huntington’s disease
includes both talk therapy and physical therapy. While there is no cure for HD right now, there is
research currently being done on a possible cure to the genetic disease due to a breakthrough in
1993. Researchers and scientists nationwide could not pin the cause of HD on any specific
genetic factor up until 1993; researchers discovered via intense research and technological
advancements that when the cytoplasmic protein huntingtin (mHtt), which is located in the short
arm of chromosome four, had more than thirty-six glutamine residues (abnormal) rather than less
(normal), the patient would have Huntington’s Disease.
Huntingtin proteins are found in every cell in the body. The genetic code for the
huntingtin protein can be found in the nucleus of the cell where genetic information is stored.
DNA which contains hereditary information and genetic instructions can be found in the
Nucleus, which serves as storage for the DNA and the majority of genetic material within the
cell. The nucleus also directs the cell’s activities, growth, reproduction, metabolism, and protein
synthesis. In a nerve cell, the type of cell that is affected by HD, the nucleus is responsible for
storing the DNA and directing the cell’s activities. The function of neurons is to communicate
messages to and from the cranial and spinal cavities via electrochemical processes, which would
be regulated by the nucleus. Depending on the type of neuron, afferent or efferent, nuclei
interpret, send, and receive messages from other nuclei in their respective part of the nervous
system.
Although the function of the huntingtin protein is currently unknown, scientists have
been able to infer through experimentation that mHtt interacts with both huntingtin’s interactor
protein (HIP-1) and huntingtin’s associated protein (HAP-1) which can only be found in the
brain. This finding can explain why only cells in the brain die when a patient has the abnormal
amount of glutamine residues in the huntingtin protein despite the protein being found in every
cell of the patient’s body. The number of C-A-G repeats in the huntington gene determines how
the huntingtin protein interacts with HIP-1 and HAP-1. In a normal huntington gene, there are
less than thirty-six glutamine residues of the repeating C-A-G triplet. When that number
surpasses thirty-six, the huntingtin protein consequently binds less to HIP-1 and more to HAP-1.
One of many theories attempting to explain the death of neurons in HD patients discusses how
the abnormal mHtt gene causes neurons to go through apoptosis (cell-suicide) at a much more
accelerated rate than normal. The theory explains how HD patients’ neurons have neuronal
inclusions of the abnormal huntingtin protein that only contain a segments of the full protein
suggesting that at some point the protein is cut into fragments, with some within and outside of
the nucleus. The apoptosis directed by the nucleus would, in theory, cause all of the organelles to
cease their regular functions and die of the affected cells. Neither physical therapy nor talk
therapy will help the nuclei of the abnormal cells perform their regular tasks. What the therapies
offer, however, are methods to make life less painful for the affected patients and their family
members/friends. Physical therapy can help limit chorea and allow for more controlled
movement for patients in the later stages of the disease while talk therapy may help family
members and patients in the earlier stages of the disease recognize and cope with the diagnosis.
WORKS CITED
Davidson, Michael W. "Molecular Expressions Cell Biology: The Cell Nucleus."Molecular
Expressions Cell Biology: The Cell Nucleus. Florida State University, 1 Oct. 2000. Web.
29 Sept. 2016.
Liou, By Stephanie. "HOPES." The Basic Neurobiology of Huntington’s Disease (Text and
Audio). Stanford University, 26 June 2010. Web. 29 Sept. 2016.
"What Is Huntington's Disease?" Huntingtons Desease Society of America What Is HD
Comments. Huntington's Disease Society of America, n.d. Web. 29 Sept. 2016.