Perinuclear localization of huntingtin as a consequence of its binding to microtubules through an interaction with β-tubulin: relevance to Huntington's disease

2002 ◽  
Vol 115 (5) ◽  
pp. 941-948 ◽  
Author(s):  
Guylaine Hoffner ◽  
Pascal Kahlem ◽  
Philippe Djian
Keyword(s):  
Electron Microscopy ◽  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Binding Property ◽  
Perinuclear Region ◽  
Β Subunit ◽  
Tubulin Binding ◽  
Β Tubulin

Huntington's disease results from an expansion of a series of glutamine repeats in the protein huntingtin. We have discovered from immunopurification studies that huntingtin combines specifically with the β subunit of tubulin. This binding explains why huntingtin can be shown on assembled microtubules by electron microscopy. Immunostaining shows that most of the huntingtin in the cytoplasm is associated with microtubules. Huntingtin is particularly abundant in the perinuclear region, where it is also associated with microtubules and in the centrosomal region, where it co-localizes withγ-tubulin. In Huntington's disease, inclusions are often nuclear or perinuclear. Since the perinuclear concentration of huntingtin does not depend on the number of its glutamine repeats, we propose that inclusions are found in perinuclear and intranuclear locations because the β-tubulin binding property of huntingtin brings it to the perinuclear region, from which it readily gains access to the nucleus. The mutational glutamine expansion then promotes insolubility and results in an inclusion.

scholarly journals A mouse model of Huntington’s disease shows altered ultrastructure of transverse tubules in skeletal muscle fibers

2021 ◽  
Vol 153 (4) ◽  
Author(s):  
Shannon H. Romer ◽  
Sabrina Metzger ◽  
Kristiana Peraza ◽  
Matthew C. Wright ◽  
D. Scott Jobe ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Skeletal Muscle ◽  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Muscle Fibers ◽  
Membrane Capacitance ◽  
Mrna Levels ◽  
Primary Role ◽  
Ec Coupling ◽  
Skeletal Muscle Fibers

Huntington’s disease (HD) is a fatal and progressive condition with severe debilitating motor defects and muscle weakness. Although classically recognized as a neurodegenerative disorder, there is increasing evidence of cell autonomous toxicity in skeletal muscle. We recently demonstrated that skeletal muscle fibers from the R6/2 model mouse of HD have a decrease in specific membrane capacitance, suggesting a loss of transverse tubule (t-tubule) membrane in R6/2 muscle. A previous report also indicated that Cav1.1 current was reduced in R6/2 skeletal muscle, suggesting defects in excitation–contraction (EC) coupling. Thus, we hypothesized that a loss and/or disruption of the skeletal muscle t-tubule system contributes to changes in EC coupling in R6/2 skeletal muscle. We used live-cell imaging with multiphoton confocal microscopy and transmission electron microscopy to assess the t-tubule architecture in late-stage R6/2 muscle and found no significant differences in the t-tubule system density, regularity, or integrity. However, electron microscopy images revealed that the cross-sectional area of t-tubules at the triad were 25% smaller in R6/2 compared with age-matched control skeletal muscle. Computer simulation revealed that the resulting decrease in the R6/2 t-tubule luminal conductance contributed to, but did not fully explain, the reduced R6/2 membrane capacitance. Analyses of bridging integrator-1 (Bin1), which plays a primary role in t-tubule formation, revealed decreased Bin1 protein levels and aberrant splicing of Bin1 mRNA in R6/2 muscle. Additionally, the distance between the t-tubule and sarcoplasmic reticulum was wider in R6/2 compared with control muscle, which was associated with a decrease in junctophilin 1 and 2 mRNA levels. Altogether, these findings can help explain dysregulated EC coupling and motor impairment in Huntington’s disease.

scholarly journals Correlative light and electron microscopy suggests that mutant huntingtin dysregulates the endolysosomal pathway in presymptomatic Huntington’s disease

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Ya Zhou ◽  
Thomas R. Peskett ◽  
Christian Landles ◽  
John B. Warner ◽  
Kirupa Sathasivam ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Neurodegenerative Disorder ◽  
Late Onset ◽  
Light And Electron Microscopy ◽  
Yeast Cells ◽  
Disease Stage ◽  
Dependent Manner ◽  
Residual Bodies

AbstractHuntington’s disease (HD) is a late onset, inherited neurodegenerative disorder for which early pathogenic events remain poorly understood. Here we show that mutant exon 1 HTT proteins are recruited to a subset of cytoplasmic aggregates in the cell bodies of neurons in brain sections from presymptomatic HD, but not wild-type, mice. This occurred in a disease stage and polyglutamine-length dependent manner. We successfully adapted a high-resolution correlative light and electron microscopy methodology, originally developed for mammalian and yeast cells, to allow us to correlate light microscopy and electron microscopy images on the same brain section within an accuracy of 100 nm. Using this approach, we identified these recruitment sites as single membrane bound, vesicle-rich endolysosomal organelles, specifically as (1) multivesicular bodies (MVBs), or amphisomes and (2) autolysosomes or residual bodies. The organelles were often found in close-proximity to phagophore-like structures. Immunogold labeling localized mutant HTT to non-fibrillar, electron lucent structures within the lumen of these organelles. In presymptomatic HD, the recruitment organelles were predominantly MVBs/amphisomes, whereas in late-stage HD, there were more autolysosomes or residual bodies. Electron tomograms indicated the fusion of small vesicles with the vacuole within the lumen, suggesting that MVBs develop into residual bodies. We found that markers of MVB-related exocytosis were depleted in presymptomatic mice and throughout the disease course. This suggests that endolysosomal homeostasis has moved away from exocytosis toward lysosome fusion and degradation, in response to the need to clear the chronically aggregating mutant HTT protein, and that this occurs at an early stage in HD pathogenesis.

scholarly journals Microglial physiological properties and interactions with synapses are altered at presymptomatic stages in a mouse model of Huntington's disease pathology

2019 ◽  
Author(s):  
Julie Savage ◽  
Marie-Kim St-Pierre ◽  
Micaël Carrier ◽  
Hassan El Hajj ◽  
Sammy Novak ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Mouse Model ◽  
Light Microscopy ◽  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Cag Repeats ◽  
Motor Deficits ◽  
Synaptic Density ◽  
Transmission Electron

Abstract Background: Huntington’s disease (HD) is a dominantly inherited neurodegenerative disorder that affects cognitive and motor abilities by primarily targeting the striatum and cerebral cortex. HD is caused by a mutation elongating the CAG repeats within the Huntingtin gene, resulting in HTT protein misfolding. Although the genetic cause of HD has been established, the specific susceptibility of neurons within various brain structures has remained elusive. Microglia, which are the brain’s resident macrophages, have emerged as important players in neurodegeneration. Nevertheless, few studies have examined their implication in HD. Methods: To provide novel insights, we investigated the maturation and dysfunction of striatal microglia using the R6/2 mouse model of HD. This transgenic model, which presents with 120+/-5 CAG repeats, displays progressive motor deficits beginning at 6 weeks of age, with full incapacitation by 13 weeks. We studied microglial morphology, phagocytic capacity, and synaptic contacts in the striatum of R6/2 versus wild-type (WT) littermates at 3, 10 and 13 weeks of age, using a combination of light and transmission electron microscopy. We also reconstructed dendrites and determined synaptic density within the striatum of R6/2 and WT littermates, at nanoscale resolution using focused ion beam-scanning electron microscopy. Results: At 3 weeks of age, prior to any known motor deficits, light microscopy studies revealed that microglia in R6/2 animals displayed a mature morphological phenotype, not reached by microglia in WT animals until 7-10 weeks of age. Microglia from R6/2 mice across all ages investigated also demonstrated increased phagocytosis, as revealed by light microscopy and transmission electron microscopy. Furthermore, microglial processes from 10-week old R6/2 mice made fewer contacts with synaptic structures than those of 3-week old R6/2 mice and age-matched WT littermates. While synaptic density was not affected by genotype at 3 weeks of age, it only increased with maturation in WT mice between 3 and 10 weeks of age. The location of synapses was lastly modified from targeting dendritic spines to trunks at 3 and 10 weeks of age in R6/2 mice versus WT controls. Conclusions: These findings suggest that microglia may play an intimate role in synaptic alteration and loss during HD pathogenesis.

scholarly journals Correlative light and electron microscopy reveals that mutant huntingtin dysregulates the endolysosomal pathway in presymptomatic Huntington’s disease

2021 ◽  
Author(s):  
Ya Zhou ◽  
Thomas R. Peskett ◽  
Christian Landles ◽  
John B. Warner ◽  
Kirupa Sathasivam ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Neurodegenerative Disorder ◽  
Late Onset ◽  
Light And Electron Microscopy ◽  
Yeast Cells ◽  
Disease Stage ◽  
Dependent Manner ◽  
Residual Bodies

AbstractHuntington’s disease (HD) is a late onset, inherited neurodegenerative disorder for which early pathogenic events remain poorly understood. Here we show that mutant exon 1 HTT proteins are recruited to a subset of cytoplasmic aggregates in the cell bodies of neurons in brain sections from presymptomatic HD, but not wild-type, mice. This occurred in a disease stage and polyglutamine-length dependent manner. We successfully adapted a high-resolution correlative light and electron microscopy methodology, originally developed for mammalian and yeast cells, to allow us to correlate light microscopy and electron microscopy images on the same brain section within an accuracy of 100 nm. Using this approach, we identified these recruitment sites as single membrane bound, vesicle-rich endolysosomal organelles, specifically as (i) multivesicular bodies (MVBs), or amphisomes and (ii) autolysosomes or residual bodies. The organelles were often found in close proximity to phagophore-like structures. Immunogold labeling localized mutant HTT to non-fibrillar, electron lucent structures within the lumen of these organelles. In presymptomatic HD, the recruitment organelles were predominantly MVBs/amphisomes, whereas in late-stage HD, there were more autolysosomes or residual bodies. Electron tomograms indicated the fusion of small vesicles with the vacuole within the lumen, suggesting that MVBs develop into residual bodies. We found that markers of MVB-related exocytosis were depleted in presymptomatic mice and throughout the disease course. This suggests that endolysosomal homeostasis has moved away from exocytosis toward lysosome fusion and degradation, in response to the need to clear the chronically aggregating mutant HTT protein, and that this occurs at an early stage in HD pathogenesis.

Exclusion of DNA changes in the β–subunit of the c–GMP phosphodiesterase gene as the cause for Huntington's disease

1992 ◽  
Vol 1 (2) ◽  
pp. 104-108 ◽  
Author(s):  
Olaf Riess ◽  
Anne Noerremoelle ◽  
Colin Collins ◽  
Diana Mah ◽  
Bernhard Weber ◽  
...  
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Β Subunit
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