Huntington Disease: The Complexities of Making and Disclosing a Clinical Diagnosis After Premanifest Genetic Testing

Non-Cell Autonomous and Epigenetic Mechanisms of Huntington's Disease

Huntington's disease (HD) is a rare neurodegenerative disorder caused by an expansion of CAG trinucleotide repeat located in the exon 1 of Huntingtin (HTT) gene in human chromosome 4. The HTT protein is ubiquitously expressed in the brain. Specifically, mutant HTT (mHTT) protein-mediated toxicity leads to a dramatic degeneration of the striatum among many regions of the brain. HD symptoms exhibit a major involuntary movement followed by cognitive and psychiatric dysfunctions. In this review, we address the conventional role of wild type HTT (wtHTT) and how mHTT protein disrupts the function of medium spiny neurons (MSNs). We also discuss how mHTT modulates epigenetic modifications and transcriptional pathways in MSNs. In addition, we define how non-cell autonomous pathways lead to damage and death of MSNs under HD pathological conditions. Lastly, we overview therapeutic approaches for HD. Together, understanding of precise neuropathological mechanisms of HD may improve therapeutic approaches to treat the onset and progression of HD.

Genetic Risk of Alzheimer's Disease: Three Wishes Now That the Genie is Out of the Bottle

The availability and increasing popularity of direct-to-consumer genetic testing for the presence of an APOE4 allelle led the Alzheimer's Foundation of America Medical, Scientific and Memory Screening Advisory Board to identify three critical areas for attention: 1) ensure consumer understanding of test results; 2) address and limit potential negative consequences of acquiring this information; and 3) support linking results with positive health behaviors, including potential clinical trial participation. Improving access to appropriate sources of genetic counseling as part of the testing process is critical and requires action from clinicians and the genetic testing industry. Standardizing information and resources across the industry should start now, with the input of consumers and experts in genetic risk and health information disclosure. Direct-to-consumer testing companies and clinicians should assist consumers by facilitating consultation with genetic counselors and facilitating pursuit of accurate information about testing.

Genetic Counseling in Huntington's Disease: Potential New Challenges on Horizon?

Huntington's disease (HD) is a rare, hereditary, neurodegenerative and dominantly transmitted disorder affecting about 10 out of 100,000 people in Western Countries. The genetic cause is a CAG repeat expansion in the huntingtin gene (HTT), which is unstable and may further increase its length in subsequent generations, so called anticipation. Mutation repeat length coupled with other gene modifiers and environmental factors contribute to the age at onset in the offspring. Considering the unpredictability of age at onset and of clinical prognosis in HD, the accurate interpretation, a proper psychological support and a scientifically sound and compassionate communication of the genetic test result are crucial in the context of Good Clinical Practice and when considering further potential disease-modifying therapies. We discuss various genetic test scenarios that require a particularly careful attention in psychological and genetic counseling and expect that the counseling procedures will require a constant update.