Related Experiment Video
Updated: Jun 11, 2025
Fractionation for Resolution of Soluble and Insoluble Huntingtin Species
Published on: February 27, 2018
Poly ADP-ribose signaling is dysregulated in Huntington disease
Tamara Maiuri1, Carlos Barba Bazan1, Rachel J Harding2,3,4
1Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 3Z5, Canada.
Insights
Huntington disease (HD) involves DNA damage and altered poly (ADP-ribose) (PAR) levels. Mutant Huntingtin protein affects PARP1 activity, suggesting new therapeutic targets for early intervention.
Area of Science:
- Neuroscience
- Genetics
- Molecular Biology
Background:
- Huntington disease (HD) is a genetic neurodegenerative disorder caused by CAG repeat expansion in the Huntingtin (HTT) gene.
- While CAG repeat length correlates with onset age, significant variability exists, suggesting other genetic or molecular factors are involved.
- Elevated DNA damage and dysfunction in DNA repair pathways, including the PARP pathway, are implicated in HD pathogenesis.
Purpose of the Study:
- To investigate the role of poly (ADP-ribose) (PAR) metabolism in Huntington disease.
- To explore the interaction between the Huntingtin protein (HTT) and the PARP pathway.
- To identify potential early molecular mechanisms and therapeutic targets for HD.
Main Methods:
- Measurement of cerebrospinal fluid PAR levels in HD mutation carriers and controls.
- Analysis of PAR response in patient-derived induced pluripotent stem cell-derived neurons and fibroblasts.
- Biochemical assays to detect HTT-PAR binding and assess HTT's effect on PARP1 activity.
- Single-molecule visualization of HTT-PAR interactions using atomic force microscopy.
Main Results:
- HD mutation carriers exhibit reduced cerebrospinal fluid PAR levels, even in the premanifest stage.
- HD cells show a diminished PAR response despite elevated DNA damage.
- Huntingtin protein (HTT) binds to PARylated proteins and localizes to mitotic chromosomes.
- Wild-type HTT enhances in vitro PARP1 activity, whereas mutant HTT does not.
Conclusions:
- Altered PAR levels and impaired PAR response are early molecular events in Huntington disease.
- The Huntingtin protein interacts with the PARP pathway, with functional differences between wild-type and mutant forms.
- These findings suggest that targeting the PARP pathway could offer a strategy for early preventive therapies in HD.
Abstract:
Huntington disease (HD) is a genetic neurodegenerative disease caused by cytosine, adenine, guanine (CAG) expansion in the Huntingtin (HTT) gene, translating to an expanded polyglutamine tract in the HTT protein. Age at disease onset correlates to CAG repeat length but varies by decades between individuals with identical repeat lengths. Genome-wide association studies link HD modification to DNA repair and mitochondrial health pathways. Clinical studies show elevated DNA damage in HD, even at the premanifest stage. A major DNA repair node influencing neurodegenerative disease is the PARP pathway. Accumulation of poly adenosine diphosphate (ADP)-ribose (PAR) has been implicated in Alzheimer and Parkinson diseases, as well as cerebellar ataxia. We report that HD mutation carriers have lower cerebrospinal fluid PAR levels than healthy controls, starting at the premanifest stage. Human HD induced pluripotent stem cell-derived neurons and patient-derived fibroblasts have diminished PAR response in the context of elevated DNA damage. We have defined a PAR-binding motif in HTT, detected HTT complexed with PARylated proteins in human cells during stress, and localized HTT to mitotic chromosomes upon inhibition of PAR degradation. Direct HTT PAR binding was measured by fluorescence polarization and visualized by atomic force microscopy at the single molecule level. While wild-type and mutant HTT did not differ in their PAR binding ability, purified wild-type HTT protein increased in vitro PARP1 activity while mutant HTT did not. These results provide insight into an early molecular mechanism of HD, suggesting possible targets for the design of early preventive therapies.
More Related Videos
10:52Efficient and Scalable Production of Full-length Human Huntingtin Variants in Mammalian Cells using a Transient Expression System
Published on: December 10, 2021
11:22Generation of Native, Untagged Huntingtin Exon1 Monomer and Fibrils Using a SUMO Fusion Strategy
Published on: June 27, 2018
Related Concept Videos
02:33Hedgehog Signaling Pathway
03:14Notch Signaling Pathway
The Notch gene came into the limelight in 1914 after the discovery that its mutation in Drosophila melanogaster leads to a serrated (or "notched") wing margin phenotype. It was not...
01:19Interactions Between Signaling Pathways
Convergence and divergence, and cross-talk between signaling pathways
Two distinct signaling pathways can converge on a single functional unit, which may either be a single protein or a complex of proteins. The response is either functionally distinct or synergistic between the two pathways but different from the response...
01:19Allosteric Proteins-ATCase
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis...
02:18Alternative RNA Splicing
There are five types of alternative RNA splicing that vary in the ways the pre-mRNA segments are removed or retained in the mature mRNA. The first...
02:15Experimental RNAi