Cerebrospinal fluid mutant huntingtin is a biomarker for huntingtin lowering in the striatum of Huntington disease mice

Caron, Nicholas S.; Banos, Raul; Aly, Amirah E-E; Xie, Yuanyun; Ko, Seung‐Hyun; Potluri, Nalini; Anderson, Christine; Black, Hailey Findlay; Anderson, Lisa; Gordon, Benjamin; Hayden, Michael R.

doi:10.1016/j.nbd.2022.105652

Cited by 15 publications

(8 citation statements)

References 30 publications

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“…The solution can be a highly sensitive transcript assay, like the one described in this study. Since measurements of the mutant gene expression level are also considered as important biomarker in polyQ diseases [ 37 , 62 , 63 ], our approach can be considered as a powerful tool in clinical research.…”

Section: Discussionmentioning

confidence: 99%

Allele-specific quantitation of ATXN3 and HTT transcripts in polyQ disease models

et al. 2023

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Background The majority of genes in the human genome is present in two copies but the expression levels of both alleles is not equal. Allelic imbalance is an aspect of gene expression relevant not only in the context of genetic variation, but also to understand the pathophysiology of genes implicated in genetic disorders, in particular, dominant genetic diseases where patients possess one normal and one mutant allele. Polyglutamine (polyQ) diseases are caused by the expansion of CAG trinucleotide tracts within specific genes. Spinocerebellar ataxia type 3 (SCA3) and Huntington’s disease (HD) patients harbor one normal and one mutant allele that differ in the length of CAG tracts. However, assessing the expression level of individual alleles is challenging due to the presence of abundant CAG repeats in the human transcriptome, which make difficult the design of allele-specific methods, as well as of therapeutic strategies to selectively engage CAG sequences in mutant transcripts. Results To precisely quantify expression in an allele-specific manner, we used SNP variants that are linked to either normal or CAG expanded alleles of the ataxin-3 (ATXN3) and huntingtin (HTT) genes in selected patient-derived cell lines. We applied a SNP-based quantitative droplet digital PCR (ddPCR) protocol for precise determination of the levels of transcripts in cellular and mouse models. For HD, we showed that the process of cell differentiation can affect the ratio between endogenous alleles of HTT mRNA. Additionally, we reported changes in the absolute number of the ATXN3 and HTT transcripts per cell during neuronal differentiation. We also implemented our assay to reliably monitor, in an allele-specific manner, the silencing efficiency of mRNA-targeting therapeutic approaches for HD. Finally, using the humanized Hu128/21 HD mouse model, we showed that the ratio of normal and mutant HTT transgene expression in brain slightly changes with the age of mice. Conclusions Using allele-specific ddPCR assays, we observed differences in allele expression levels in the context of SCA3 and HD. Our allele-selective approach is a reliable and quantitative method to analyze low abundant transcripts and is performed with high accuracy and reproducibility. Therefore, the use of this approach can significantly improve understanding of allele-related mechanisms, e.g., related with mRNA processing that may be affected in polyQ diseases.

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Section: Discussionmentioning

confidence: 99%

Allele-specific quantitation of ATXN3 and HTT transcripts in polyQ disease models

et al. 2023

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“…3A). The HTT ASO used in this study targets the human mutant HTT transgene in YAC128 mice without altering levels of mouse Htt (99).…”

Section: Acute Neurodegeneration In the Striatum Of Yac128 Mice Leads...mentioning

confidence: 99%

Plasma and CSF neurofilament light chain are stabilized in response to mutant huntingtin lowering in the brain of Huntington disease mice

Caron,

Byrne,

Lemarié

et al. 2024

Preprint

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Background Therapeutic approaches aimed at lowering levels of toxic mutant huntingtin (mHTT) in the brain can reverse disease phenotypes in animal models of Huntington disease (HD) and are currently being evaluated in clinical trials. Sensitive and dynamic response biomarkers are needed to assess the efficacy of such candidate therapies. Neurofilament light chain (NfL) is a biomarker of neurodegeneration that increases in cerebrospinal fluid (CSF) and blood with HD progression. However, it remains unknown whether NfL in biofluids may be useful as a response biomarker for assessing the efficacy of disease-modifying therapies for HD. Methods Longitudinal plasma and cross-sectional CSF samples were collected from the YAC128 transgenic mouse model of HD and wild type littermate control mice throughout the natural history of disease. Additionally, biofluids were collected from YAC128 mice following intracerebroventricular administration of an antisense oligonucleotide targeting the mutant HTT transgene (HTT ASO) at ages either before or after the onset of disease phenotypes. NfL concentrations in plasma and CSF were quantified using ultrasensitive single-molecule array technology. Results Plasma and CSF NfL concentrations were significantly elevated in YAC128 compared to wild type littermate control mice from 9 months of age. Treatment of YAC128 mice with either 15 or 50 µg HTT ASO resulted in dose-dependent, allele-selective reduction of mHTT throughout the brain at a 3-month interval, which was sustained with high dose HTT ASO treatment up 6 months. Lowering of mHTT in the brain with HTT ASO initiated prior to the onset of regional brain atrophy and HD-like motor deficits in YAC128 mice had minimal effect on plasma NfL at either dose but resulted in a dose-dependent reduction of CSF NfL. In contrast, initiating mHTT lowering in the brain after the onset of neuropathological and behavioural phenotypes in YAC128 mice resulted in a dose-dependent stabilization of NfL increases in both plasma and CSF. Conclusions Our data provides evidence that the response of NfL in biofluids is influenced by the magnitude of mHTT lowering in the brain and the timing of intervention, suggesting that NfL may represent a promising exploratory response biomarker for HD.

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“…Thanks to this system, it is feasible to quantify soluble mHTT in CSF, of which the concentration is higher in symptomatic than pre-symptomatic individuals and in later stages of the disease, and correlates positively with the motor score (namely, the Unified HD Rating Scale or UHDRS) and cognitive performance [ 40 ]. Despite these observations, mHTT monitoring does not improve the prognostic performance of other neurodegenerative markers that are easy to detect [ 41 ] (see below), but can still be useful to assess mHTT-lowering therapeutics [ 42 ].…”

Section: Huntingtinmentioning

confidence: 99%

A Glimpse of Molecular Biomarkers in Huntington’s Disease

Martí-Martínez

Valor

2022

IJMS

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Huntington’s disease (HD) is a devastating neurodegenerative disorder that is caused by an abnormal expansion of CAG repeats in the Huntingtin (HTT) gene. Although the main symptomatology is explained by alterations at the level of the central nervous system, predominantly affecting the basal ganglia, a peripheral component of the disease is being increasingly acknowledged. Therefore, the manifestation of the disease is complex and variable among CAG expansion carriers, introducing uncertainty in the appearance of specific signs, age of onset and severity of disease. The monogenic nature of the disorder allows a precise diagnosis, but the use of biomarkers with prognostic value is still needed to achieve clinical management of the patients in an individual manner. In addition, we need tools to evaluate the patient’s response to potential therapeutic approaches. In this review, we provide a succinct summary of the most interesting molecular biomarkers that have been assessed in patients, mostly obtained from body fluids such as cerebrospinal fluid, peripheral blood and saliva.

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Cerebrospinal fluid mutant huntingtin is a biomarker for huntingtin lowering in the striatum of Huntington disease mice

Cited by 15 publications

References 30 publications

Allele-specific quantitation of ATXN3 and HTT transcripts in polyQ disease models

Allele-specific quantitation of ATXN3 and HTT transcripts in polyQ disease models

Plasma and CSF neurofilament light chain are stabilized in response to mutant huntingtin lowering in the brain of Huntington disease mice

A Glimpse of Molecular Biomarkers in Huntington’s Disease

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