Huntington's Disease

Definition

Huntington's disease is a hereditary neurodegenerative disorder caused by the expansion of CAG repeats in the HTT gene, leading to progressive motor dysfunction, cognitive decline, and psychiatric symptoms. This condition highlights the role of gene regulatory networks, as the abnormal protein produced interferes with normal cellular functions and regulation of gene expression in neurons.

5 Must Know Facts For Your Next Test

1. Huntington's disease typically manifests between ages 30 and 50 and is characterized by chorea, or involuntary movements.
2. The condition follows an autosomal dominant inheritance pattern, meaning that an affected individual has a 50% chance of passing it on to their offspring.
3. The HTT gene responsible for Huntington's disease is located on chromosome 4 and has a normal range of 10-35 CAG repeats; expansions beyond this range lead to the disease.
4. Symptoms often worsen over time, leading to severe disability and complications such as pneumonia and heart failure due to immobility.
5. Research into Huntington's disease has spurred advances in gene therapy and potential treatments aimed at silencing or editing the faulty gene.

Review Questions

• How does the CAG repeat expansion in the HTT gene contribute to the symptoms observed in Huntington's disease?
  • The CAG repeat expansion in the HTT gene results in an abnormal protein that disrupts normal cellular processes, particularly in neurons. This abnormal protein leads to toxic gain-of-function effects, affecting neurotransmitter release and neuronal health. Consequently, patients experience symptoms such as motor dysfunction, cognitive decline, and psychiatric disturbances due to the impaired functioning of their neural circuits.
• Discuss the role of gene regulatory networks in the pathology of Huntington's disease and how they can be targeted for potential therapies.
  • Gene regulatory networks are critical in understanding how Huntington's disease progresses since they dictate how genes are expressed in response to various signals. In this disorder, the dysregulation caused by the mutant HTT protein alters the expression of many genes involved in neuronal survival and function. Targeting these networks through gene therapy or small molecules could potentially restore normal gene expression patterns, offering new avenues for treating or mitigating the disease.
• Evaluate the implications of Huntington's disease on families affected by it, particularly regarding genetic counseling and decision-making for future generations.
  • Huntington's disease poses significant challenges for families due to its hereditary nature. Individuals at risk often face tough decisions about genetic testing and family planning, knowing that a positive result means a 50% chance of passing on the condition. Genetic counseling plays a vital role in helping families navigate these choices by providing information on inheritance patterns, discussing emotional impacts, and exploring reproductive options such as preimplantation genetic diagnosis. The emotional burden and uncertainty surrounding this disease also highlight the importance of support systems for affected individuals and their families.

Related terms

CAG Repeat Expansion: A genetic mutation characterized by the repetition of the cytosine-adenine-guanine sequence within the HTT gene, directly linked to Huntington's disease.

Neurodegeneration: The progressive loss of structure or function of neurons, which is a key feature of Huntington's disease, leading to symptoms such as movement disorders and cognitive decline.

Gene Expression Regulation: The control of the timing and amount of gene expression, crucial in understanding how Huntington's disease affects neuronal function and health.