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Huntington's DiseaseCAG count range from 28-35? Be very careful!

New Study Reveals Genetic Variations in Chinese Patients with Huntington's Disease


A recent study conducted in China has shed new light on the genetic characteristics of individuals with Huntington's disease (HD), a neurodegenerative disorder that affects motor skills, cognitive function, and behavior. The research, led by Dr. Yu-Feng Bao and his team, focused on the loss of CAA interruption (LOI) and intergenerational CAG instability in the HTT gene, which is responsible for causing HD.


Huntington's disease is known to be caused by the expansion of CAG repeats in the HTT gene, leading to the production of a mutant huntingtin protein that progressively damages brain cells. However, the severity and onset of symptoms can vary greatly among affected individuals due to genetic modifiers and instability in the CAG repeats.

For this study, the researchers recruited a total of 229 HD patients from 164 families who carried expanded CAG repeats in the HTT gene. They performed genetic testing and analyzed the presence of LOI variants and CAG instability during the transmission of genetic material from one generation to the next.

Using advanced sequencing techniques, the team identified six individuals with LOI variants from three different families. Interestingly, all these individuals showed an earlier onset of motor symptoms compared to what was predicted based on their CAG repeat lengths. This suggests that LOI variants may contribute to an accelerated progression of Huntington's disease.

In addition, the study also highlighted two families with extreme CAG instability during germline transmission. In one family, the CAG repeat length expanded from 35 to 66 repeats, while the other family exhibited both CAG expansion and contraction across three generations. This finding emphasizes the dynamic nature of CAG repeats and their potential to change in length during the transmission of genetic material.

The discovery of LOI variants in Asian patients with Huntington's disease is significant as it provides valuable insights into the genetic diversity of HD populations. The researchers recommend that HTT gene sequencing should be considered in clinical practice for symptomatic individuals who have intermediate or reduced penetrance alleles or a negative family history of the disease. This would help in accurate diagnosis and provide a better understanding of disease progression in these cases.

Overall, this study deepens our understanding of the genetic factors contributing to Huntington's disease and highlights the importance of comprehensive genetic testing in clinical settings. Further research in this field will be crucial for developing targeted treatments and personalized care for individuals affected by this devastating neurodegenerative disorder.

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