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Published on: July 14, 2016
The gene coding for PGC-1alpha modifies age at onset in Huntington's Disease
Patrick Weydt1, Selma M Soyal, Cinzia Gellera
1Department of Neurology, University of Ulm (P,W,; G,B,L,), Ulm, Germany. patrick.weydt@uni-ulm.de.
Insights
Huntington's disease (HD) onset is influenced by genetic factors beyond CAG repeats. Specific variants in the PGC-1alpha gene (PPARGC1A) can significantly delay disease progression in patients.
Area of Science:
- Neurogenetics
- Mitochondrial Biology
- Neurodegenerative Diseases
Background:
- Huntington's disease (HD) is an inherited neurodegenerative disorder characterized by motor, emotional, and cognitive decline.
- Metabolic abnormalities, including wasting and altered energy expenditure, are recognized hallmarks of HD.
- HD pathogenesis involves transcriptional dysregulation, mitochondrial dysfunction, and oxidative stress, with PGC-1alpha (encoded by PPARGC1A) identified as a potentially defective regulator.
Purpose of the Study:
- To investigate the association between genetic variations in the PPARGC1A gene and the age of onset in Huntington's disease patients.
- To determine if specific haplotypes of PPARGC1A influence disease progression, independent of CAG repeat length in the HTT gene.
Main Methods:
- Analysis of 2-loci PPARGC1A block 2 haplotypes in 447 unrelated Huntington's disease patients.
- Statistical consideration of CAG repeat lengths in both HTT alleles to isolate the effect of PPARGC1A haplotypes on age-at-onset.
- Comparison of disease onset age between patients with different PPARGC1A haplotype combinations.
Main Results:
- PPARGC1A block 2 haplotypes, but not block 1 haplotypes, were associated with the age of onset in HD patients.
- Homozygosity for a specific 'protective' block 2 haplotype significantly delayed the onset of Huntington's disease.
- This finding was statistically significant after accounting for the length of CAG repeats in the HTT gene.
Conclusions:
- The PGC-1alpha system, through variations in the PPARGC1A gene, plays a clinically relevant role in modulating the age of onset for Huntington's disease in humans.
- This study provides the first evidence of a genetic modifier effect of PGC-1alpha on HD progression in a human cohort.
- Identifying genetic modifiers like PPARGC1A could offer new therapeutic targets for delaying Huntington's disease onset and progression.
Abstract:
Huntington's disease (HD) is one of the most common autosomal dominant inherited, neurodegenerative disorders. It is characterized by progressive motor, emotional and cognitive dysfunction. In addition metabolic abnormalities such as wasting and altered energy expenditure are increasingly recognized as clinical hallmarks of the disease. HD is caused by an unstable CAG repeat expansion in the HD gene (HTT), localized on chromosome 4p16.3. The number of CAG repeats in the HD gene is the main predictor of disease-onset, but the remaining variation is strongly heritable. Transcriptional dysregulation, mitochondrial dysfunction and enhanced oxidative stress have been implicated in the pathogenesis. Recent studies suggest that PGC-1alpha, a transcriptional master regulator of mitochondrial biogenesis and metabolism, is defective in HD. A genome wide search for modifier genes of HD age-of-onset had suggested linkage at chromosomal region 4p16-4p15, near the locus of PPARGC1A, the gene coding for PGC-1alpha. We now present data of 2-loci PPARGC1A block 2 haplotypes, showing an effect upon age-at-onset in 447 unrelated HD patients after statistical consideration of CAG repeat lengths in both HTT alleles. Block 1 haplotypes were not associated with the age-at-onset. Homozygosity for the 'protective' block 2 haplotype was associated with a significant delay in disease onset. To our knowledge this is the first study to show clinically relevant effects of the PGC-1alpha system on the course of Huntington's disease in humans.
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