scholarly journals A critical window of CAG repeat-length correlates with phenotype severity in the R6/2 mouse model of Huntington's disease

2012 ◽  
Vol 107 (2) ◽  
pp. 677-691 ◽  
Author(s):  
Damian M. Cummings ◽  
Yasaman Alaghband ◽  
Miriam A. Hickey ◽  
Prasad R. Joshi ◽  
S. Candice Hong ◽  
...  
Keyword(s):  
Mouse Model ◽  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Age At Onset ◽  
Human Condition ◽  
Repeat Length ◽  
Cag Repeat ◽  
Cag Repeats ◽  
Drug Trials ◽  
Electrophysiological Properties

The R6/2 mouse is the most frequently used model for experimental and preclinical drug trials in Huntington's disease (HD). When the R6/2 mouse was first developed, it carried exon 1 of the huntingtin gene with ∼150 cytosine-adenine-guanine (CAG) repeats. The model presented with a rapid and aggressive phenotype that shared many features with the human condition and was particularly similar to juvenile HD. However, instability in the CAG repeat length due to different breeding practices has led to both decreases and increases in average CAG repeat lengths among colonies. Given the inverse relationship in human HD between CAG repeat length and age at onset and to a degree, the direct relationship with severity of disease, we have investigated the effect of altered CAG repeat length. Four lines, carrying ∼110, ∼160, ∼210, and ∼310 CAG repeats, were examined using a battery of tests designed to assess the basic R6/2 phenotype. These included electrophysiological properties of striatal medium-sized spiny neurons, motor activity, inclusion formation, and protein expression. The results showed an unpredicted, inverted “U-shaped” relationship between CAG repeat length and phenotype; increasing the CAG repeat length from 110 to 160 exacerbated the R6/2 phenotype, whereas further increases to 210 and 310 CAG repeats greatly ameliorated the phenotype. These findings demonstrate that the expected relationship between CAG repeat length and disease severity observed in humans is lost in the R6/2 mouse model and highlight the importance of CAG repeat-length determination in preclinical drug trials that use this model.

scholarly journals Predicting Disease Onset from Mutation Status Using Proband and Relative Data with Applications to Huntington's Disease

2012 ◽  
Vol 2012 ◽  
pp. 1-19 ◽  
Author(s):  
Tianle Chen ◽  
Yuanjia Wang ◽  
Yanyuan Ma ◽  
Karen Marder ◽  
Douglas R. Langbehn
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Family Member ◽  
Disease Onset ◽  
Repeat Length ◽  
Cag Repeat ◽  
Cag Repeats ◽  
Observational Research ◽  
Accurate Estimation ◽  
Combined Data

Huntington's disease (HD) is a progressive neurodegenerative disorder caused by an expansion of CAG repeats in the IT15 gene. The age-at-onset (AAO) of HD is inversely related to the CAG repeat length and the minimum length thought to cause HD is 36. Accurate estimation of the AAO distribution based on CAG repeat length is important for genetic counseling and the design of clinical trials. In the Cooperative Huntington's Observational Research Trial (COHORT) study, the CAG repeat length is known for the proband participants. However, whether a family member shares the huntingtin gene status (CAG expanded or not) with the proband is unknown. In this work, we use the expectation-maximization (EM) algorithm to handle the missing huntingtin gene information in first-degree family members in COHORT, assuming that a family member has the same CAG length as the proband if the family member carries a huntingtin gene mutation. We perform simulation studies to examine performance of the proposed method and apply the methods to analyze COHORT proband and family combined data. Our analyses reveal that the estimated cumulative risk of HD symptom onset obtained from the combined data is slightly lower than the risk estimated from the proband data alone.

294 Neurofilament light protein as a biomarker for huntington’s disease

2018 ◽  
Vol 89 (10) ◽  
pp. A46.2-A46
Author(s):  
Byrne Lauren ◽  
Rodrigues Filipe ◽  
Johnson Eileanoir ◽  
Solyu Kucharz Rana ◽  
Gregory Sarah ◽  
...  
Keyword(s):  
Mouse Model ◽  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Neurological Diseases ◽  
Repeat Length ◽  
Cag Repeat ◽  
Neurofilament Light ◽  
Potential Biomarker ◽  
Clinical Measures ◽  
Motor Onset

BackgroundNeurofilament light protein (NfL), a component of the axonal cytoskeleton, has been shown to be increased in cerebrospinal fluid (CSF) and blood and to respond to successful treatment in several neurological diseases. We set out to investigate NfL as a potential biomarker for Huntington’s disease (HD).MethodsWe studied NfL in plasma from 298 participants, in plasma and CSF in 37 participants, and in the R6/2 HD mouse model.ResultsNfL concentration was increased in plasma at every stage of HD including premanifest mutation carriers, rose with progression and had a striking relationship with HTT CAG repeat length. In premanifest HD, baseline plasma NfL predicted subsequent motor onset even after adjustment for age and CAG repeat length. NfL predicted clinical, cognitive and neuroimaging progression, and CSF and plasma levels were strongly associated (Byrne et al, Lancet Neurology 2017). VBM analysis revealed that NfL level predicted atrophy throughout the white matter and in the occipital grey matter (Johnson et al, Neurology 2018). In the R6/2 mouse model, NfL was increased in plasma and CSF and associated with brain volume and clinical measures (Soylu Kucharz et al, Scientific Reports 2017).ConclusionsNfL is a promising clinical and translational biomarker for HD.

scholarly journals The Contribution of Somatic Expansion of the CAG Repeat to Symptomatic Development in Huntington’s Disease: A Historical Perspective

2021 ◽  
Vol 10 (1) ◽  
pp. 7-33
Author(s):  
Darren G. Monckton
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Human Genetics ◽  
Age At Onset ◽  
Cag Repeat ◽  
Model Systems ◽  
Causative Mutation ◽  
Inverse Association ◽  
Independent Manner ◽  
Dna Mismatch

The discovery in the early 1990s of the expansion of unstable simple sequence repeats as the causative mutation for a number of inherited human disorders, including Huntington’s disease (HD), opened up a new era of human genetics and provided explanations for some old problems. In particular, an inverse association between the number of repeats inherited and age at onset, and unprecedented levels of germline instability, biased toward further expansion, provided an explanation for the wide symptomatic variability and anticipation observed in HD and many of these disorders. The repeats were also revealed to be somatically unstable in a process that is expansion-biased, age-dependent and tissue-specific, features that are now increasingly recognised as contributory to the age-dependence, progressive nature and tissue specificity of the symptoms of HD, and at least some related disorders. With much of the data deriving from affected individuals, and model systems, somatic expansions have been revealed to arise in a cell division-independent manner in critical target tissues via a mechanism involving key components of the DNA mismatch repair pathway. These insights have opened new approaches to thinking about how the disease could be treated by suppressing somatic expansion and revealed novel protein targets for intervention. Exciting times lie ahead in turning these insights into novel therapies for HD and related disorders.

scholarly journals The MID1 Protein: A Promising Therapeutic Target in Huntington’s Disease

2021 ◽  
Vol 12 ◽  
Author(s):  
Annika Heinz ◽  
Judith Schilling ◽  
Willeke van Roon-Mom ◽  
Sybille Krauß
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Protein A ◽  
Cag Repeat ◽  
Cag Repeats ◽  
Progressive Movement ◽  
Promising Therapeutic Target ◽  
Promising Therapeutic Approach ◽  
Exon 1 ◽  
Polyglutamine Protein

Huntington’s disease (HD) is caused by an expansion mutation of a CAG repeat in exon 1 of the huntingtin (HTT) gene, that encodes an expanded polyglutamine tract in the HTT protein. HD is characterized by progressive psychiatric and cognitive symptoms associated with a progressive movement disorder. HTT is ubiquitously expressed, but the pathological changes caused by the mutation are most prominent in the central nervous system. Since the mutation was discovered, research has mainly focused on the mutant HTT protein. But what if the polyglutamine protein is not the only cause of the neurotoxicity? Recent studies show that the mutant RNA transcript is also involved in cellular dysfunction. Here we discuss the abnormal interaction of the mutant HTT transcript with a protein complex containing the MID1 protein. MID1 aberrantly binds to CAG repeats and this binding increases with CAG repeat length. Since MID1 is a translation regulator, association of the MID1 complex stimulates translation of mutant HTT mRNA, resulting in an overproduction of polyglutamine protein. Thus, blocking the interaction between MID1 and mutant HTT mRNA is a promising therapeutic approach. Additionally, we show that MID1 expression in the brain of both HD patients and HD mice is aberrantly increased. This finding further supports the concept of blocking the interaction between MID1 and mutant HTT mRNA to counteract mutant HTT translation as a valuable therapeutic strategy. In line, recent studies in which either compounds affecting the assembly of the MID1 complex or molecules targeting HTT RNA, show promising results.

scholarly journals The Association between CAG Repeat Length and Age of Onset of Juvenile-Onset Huntington’s Disease

2020 ◽  
Vol 10 (9) ◽  
pp. 575 ◽  
Author(s):  
Jordan L. Schultz ◽  
Amelia D. Moser ◽  
Peg C. Nopoulos
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Age Of Onset ◽  
Repeat Length ◽  
Cag Repeat ◽  
Linear Regression Models ◽  
Juvenile Onset ◽  
Additional Information ◽  
Using Data ◽  
The Relationship

There is a known negative association between cytosine–adenine–guanine (CAG) repeat length and the age of motor onset (AMO) in adult-onset Huntington’s Disease (AOHD). This relationship is less clear in patients with juvenile-onset Huntington’s disease (JOHD), however, given the rarity of this patient population. The aim of this study was to investigate this relationship amongst a relatively large group of patients with JOHD using data from the Kids-JOHD study. Additionally, we analyzed data from the Enroll-HD platform and the Predict-HD study to compare the relationship between CAG repeat length and AMO amongst patients with AOHD to that amongst patients with JOHD using linear regression models. In line with previous reports, the variance in AMO that was predicted by CAG repeat length was 59% (p < 0.0001) in the Predict-HD study and 57% from the Enroll-HD platform (p < 0.0001). However, CAG repeat length predicted 84% of the variance in AMO amongst participants from the Kids-JOHD study (p < 0.0001). These results indicate that there may be a stronger relationship between CAG repeat length and AMO in patients with JOHD as compared to patients with AOHD. These results provide additional information that may help to model disease progression of JOHD, which is beneficial for the planning and implementation of future clinical trials.

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