Polyglutamine (polyQ) disorders are a group of nine neurodegenerative diseases that share a common genetic cause, which is an expansion of CAG repeats in the coding region of the causative genes that are otherwise unrelated. The trinucleotide expansion encodes for an expanded polyQ tract in the respective proteins, resulting in toxic gain-of-function and eventually in neurodegeneration. Currently, no disease-modifying therapies are available for this group of disorders. Nevertheless, given their monogenic nature, polyQ disorders are ideal candidates for therapies that target specifically the gene transcripts. Antisense oligonucleotides (ASOs) have been under intense investigation over recent years as gene silencing tools. ASOs are small synthetic single-stranded chains of nucleic acids that target specific RNA transcripts through several mechanisms. ASOs can reduce the levels of mutant proteins by breaking down the targeted transcript, inhibit mRNA translation or alter the maturation of the pre-mRNA via splicing correction. Over the years, chemical optimization of ASO molecules has allowed significant improvement of their pharmacological properties, which has in turn made this class of therapeutics a very promising strategy to treat a variety of neurodegenerative diseases. Indeed, preclinical and clinical strategies have been developed in recent years for some polyQ disorders using ASO therapeutics. The success of ASOs in several animal models, as well as encouraging results in the clinic for Huntington’s disease, points towards a promising future regarding the application of ASO-based therapies for polyQ disorders in humans, offering new opportunities to address unmet medical needs for this class of disorders. This review aims to present a brief overview of key chemical modifications, mechanisms of action and routes of administration that have been described for ASO-based therapies. Moreover, it presents a review of the most recent and relevant preclinical and clinical trials that have tested ASO therapeutics in polyQ disorders.

No abstract

Blood-brain barrier (BBB) disruption is a common feature in neurodegenerative diseases. However, BBB integrity has not been assessed in spinocerebellar ataxias (SCAs) such as Machado-Joseph disease/SCA type 3 (MJD/SCA3), a genetic disorder, triggered by polyglutamine-expanded ataxin-3. To investigate that, BBB integrity was evaluated in a transgenic mouse model of MJD and in human post-mortem brain tissues. Firstly, we investigated the BBB permeability in MJD mice by: i) assessing the extravasation of the Evans blue (EB) dye and blood-borne proteins (e.g fibrinogen) in the cerebellum by immunofluorescence, and ii) in vivo Dynamic Contrast Enhanced-Magnetic Resonance Imaging (DCE-MRI). The presence of ataxin-3 aggregates in brain blood vessels and the levels of tight junction (TJ)-associated proteins were also explored by immunofluorescence and western blotting. Human brain samples were used to confirm BBB permeability by evaluating fibrinogen extravasation, co-localization of ataxin-3 aggregates with brain blood vessels and neuroinflammation. In the cerebellum of the mouse model of MJD, there was a 5-fold increase in EB accumulation when compared to age-matched controls. Moreover, vascular permeability displayed a 13-fold increase demonstrated by DCE-MRI. These results were validated by the 2-fold increase in fibrinogen extravasation in transgenic animals comparing to controls. Interestingly, mutant ataxin-3 aggregates were detected in cerebellar blood vessels of transgenic mice, accompanied by alterations of TJ-associated proteins in cerebellar endothelial cells, namely a 29% decrease in claudin-5 oligomers and a 10-fold increase in an occludin cleavage fragment. These results were validated in postmortem brain samples from MJD patients as we detected fibrinogen extravasation across BBB, the presence of ataxin-3 aggregates in blood vessels and associated microgliosis.

No abstract

No abstract

Machado-Joseph disease (MJD) is an autosomal dominantly-inherited neurodegenerative disorder characterized by an over-repetition of the CAG trinucleotide of the ATXN3 gene, conferring a toxic gain-of-function to the resulting ataxin-3 protein. Despite the significant advances produced over the last years, the molecular mechanisms involved in MJD are still unclear and no treatment able to modify the disease progression is available. Aging is the major risk factor for neurodegenerative disorders, being associated with the occurrence and progression of several diseases, such as Alzheimer's, Huntington's, among others. The nuclear membrane proteins - lamins - and lamin-processing related proteins, such as ZMPSTE24, have been shown to be altered, not only during normal aging, but also in neurodegenerative disorders, such as Alzheimer's disease. Taking this into account, we aimed at investigating the role of aging in MJD by evaluating the presence of age-related markers in human and animal MJD models. Decreased levels of lamins B and C, together with decreased ZMPSTE24 levels were identified in the different MJD models. Accordingly, abnormalities in nuclear circularity, a hallmark of aging, were also observed in a N2a MJD cellular model, supporting an age-related phenotype. Furthermore, overexpressing progerin, the abnormal lamin A, generated in Hutchinson Guilford Progeria Syndrome patients that present premature and accelerated aging, in a relevant brain area of a lentiviral MJD mouse model, induced an aggravation of MJD-associated neuropathology. Our results suggest that aging is a key player in the context of MJD pathogenesis, unveiling new pathways for the development of future therapies for the disease.

No abstract