Pathoarchitectonics of the cerebral cortex in chorea-acanthocytosis and Huntington's disease

Identification of pivotal genes and pathways in Chorea-acanthocytosis using comprehensive bioinformatic analysis

Chorea-acanthocytosis (ChAc), an autosomal recessive disorder, is associated with cognitive and behavioral abnormalities. Previous studies were focused around exploring the functional annotation of VPS13A gene in ChAc, whereas the genetic labyrinth underlying this disease and plausible drug targets were underexplored. In the present study, we have identified the pivotal genes and molecular pathways implicated in ChAc using comprehensive bioinformatics analysis. In our analysis we found 27 distinct genes in Homo sapiens linked to ChAc, out of which 15 were selected as candidate genes for enrichment analysis based on their Gene Ontology (GO) annotations and involvement in relevant molecular pathways. By constructing a Protein-Protein Interaction (PPI) network consisting of 26 nodes and 62 edges, we identified two gene modules. Subsequently, using the MCODE algorithm, we identified 6 hub genes-ATN1, JPH3, TBP, VPS13A, DMD, and HTT-as core candidates. These hub genes are primarily associated with processes such as neuron development and differentiation, the CAMKK-AMPK signaling cascade, ion transmembrane transport systems, and protein localization. Furthermore, using drug gene databank we identified 23 FDA-approved drugs that possess the propensity to target 3 out of the 6 identified hub genes. We believe that our findings could open promising avenues for potential therapeutic interventions in ChAc.

Preserved VPS13A distribution and expression in Huntington's disease: divergent mechanisms of action for similar movement disorders?

VPS13A disease and Huntington's disease (HD) are two basal ganglia disorders that may be difficult to distinguish clinically because they have similar symptoms, neuropathological features, and cellular dysfunctions with selective degeneration of the medium spiny neurons of the striatum. However, their etiology is different. VPS13A disease is caused by a mutation in the VPS13A gene leading to a lack of protein in the cells, while HD is due to an expansion of CAG repeat in the huntingtin (Htt) gene, leading to aberrant accumulation of mutant Htt. Considering the similarities of both diseases regarding the selective degeneration of striatal medium spiny neurons, the involvement of VPS13A in the molecular mechanisms of HD pathophysiology cannot be discarded. We analyzed the VPS13A distribution in the striatum, cortex, hippocampus, and cerebellum of a transgenic mouse model of HD. We also quantified the VPS13A levels in the human cortex and putamen nucleus; and compared data on mutant Htt-induced changes in VPS13A expression from differential expression datasets. We found that VPS13A brain distribution or expression was unaltered in most situations with a decrease in the putamen of HD patients and small mRNA changes in the striatum and cerebellum of HD mice. We concluded that the selective susceptibility of the striatum in VPS13A disease and HD may be a consequence of disturbances in different cellular processes with convergent molecular mechanisms already to be elucidated.

An Autopsy Series of Seven Cases of VPS13A Disease (Chorea-Acanthocytosis)

BACKGROUND

Vacuolar protein sorting 13 homolog A (VPS13A) disease, historically known as chorea-acanthocytosis, is a rare neurodegenerative disorder caused by biallelic mutations in VPS13A, usually resulting in reduced or absent levels of its protein product, VPS13A. VPS13A localizes to contact sites between subcellular organelles, consistent with its recently identified role in lipid transfer between membranes. Mutations are associated with neuronal loss in the striatum, most prominently in the caudate nucleus, and associated marked astrogliosis. There are no other known disease-specific cellular changes (eg, protein aggregation), but autopsy reports to date have been limited, often lacking genetic or biochemical diagnostic confirmation.

OBJECTIVE

The goal of this study was to characterize neuropathological findings in the brains of seven patients with VPS13A disease (chorea-acanthocytosis).

METHODS

In this study, we collected brain tissues and clinical data from seven cases of VPS13A for neuropathological analysis. The clinical diagnosis was confirmed by the presence of VPS13A mutations and/or immunoblot showing the loss or reduction of VPS13A protein. Tissues underwent routine, special, and immunohistochemical staining focused on neurodegeneration. Electron microscopy was performed in one case.

RESULTS

Gross examination showed severe striatal atrophy. Microscopically, there was neuronal loss and astrogliosis in affected regions. Luxol fast blue staining showed variable lipid accumulation with diverse morphology, which was further characterized by electron microscopy. In some cases, rare degenerating p62- and ubiquitin-positive cells were present in affected regions. Calcifications were present in four cases, being extensive in one.

CONCLUSIONS

We present the largest autopsy series of biochemically and genetically confirmed VPS13A disease and identify novel histopathological findings implicating abnormal lipid accumulation. © 2023 International Parkinson and Movement Disorder Society.

EphA4 regulates white matter remyelination after ischemic stroke through Ephexin-1/RhoA/ROCK signaling pathway

Ischemic stroke, which accounts for nearly 80% of all strokes, leads to white matter injury and neurobehavioral dysfunction, but relevant therapies to inhibit demyelination or promote remyelination after white matter injury are still unavailable. In this study, the middle cerebral artery occlusion/reperfusion (MCAO/R) in vivo and oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro were used to establish the ischemic models. We found that Eph receptor A4 (EphA4) had no effect on the apoptosis of oligodendrocytes using TUNEL staining. In contrast, EphA4 promoted proliferation of oligodendrocyte precursor cells (OPCs), but reduced the numbers of mature oligodendrocytes and the levels of myelin-associated proteins (MAG, MOG, and MBP) in the process of remyelination in ischemic models in vivo and in vitro as determined using PDGFRα-EphA4-shRNA and LV-EphA4 treatments. Notably, conditional knockout of EphA4 in OPCs (EphA4^fl/fl  + AAV-PDGFRα-Cre) improved the levels of myelin-associated proteins and functional recovery following ischemic stroke. In addition, regulation of remyelination by EphA4 was mediated by the Ephexin-1/RhoA/ROCK signaling pathway. Therefore, EphA4 did not affect oligodendrocyte (OL) apoptosis but regulated white matter remyelination after ischemic stroke through the Ephexin-1/RhoA/ROCK signaling pathway. EphA4 may provide a novel and effective therapeutic target in clinical practice of ischemic stroke.

Association of sleep disturbance and freezing of gait in Parkinson disease: prevention/delay implications

STUDY OBJECTIVES

Freezing of gait (FOG) severely impairs life quality of Parkinson disease (PD) patients. The relationship between sleep disturbance and FOG in PD remains unclear, so in this study, we aimed to investigate that relationship.

METHODS

First, we assessed clinical characteristics of freezers and nonfreezers among PD patients. Next, we assessed clinical characteristics of PD patients with different PDSS1 scores (score on first item of Parkinson's Disease Sleep Scale). Finally, we prospectively followed a cohort of nonfreezers from a baseline clinical visit and to a maximum of 18 months and performed a Cox regression analysis to further investigate the relationship between PDSS1 score and FOG in PD.

RESULTS

A total of 163 participants with PD were included in the baseline analysis. The freezers had significantly worse sleep compared with the nonfreezers. The proportion of freezers in the patients with low PDSS1 score (PDSS1 < 6) was significantly higher than that in the patients with high PDSS1 score (PDSS1 ≥ 6). A total of 52 nonfreezers were prospectively followed. During a maximum 18-month follow-up, FOG incidence (73%) in the PDSS1 < 6 group was significantly higher than that (24%) in the PDSS1 ≥ 6 group (P = .008). Low PDSS1 score (hazard ratio = 4.23, 95% CI 1.64-10.92, P = .003) and high levodopa equivalent daily dose (hazard ratio = 4.18, 95% CI 1.62-10.75, P = .003) were significantly associated with an increased hazard of FOG.

CONCLUSIONS

Our study indicated that low PDSS1 score may be a risk indicator for the development of FOG and provided important insights into potential targets for the prevention/delay of FOG in PD.

Targeting Lyn Kinase in Chorea-Acanthocytosis: A Translational Treatment Approach in a Rare Disease

Background: Chorea-acanthocytosis (ChAc) is a neurodegenerative disease caused by mutations in the VPS13A gene. It is characterized by several neurological symptoms and the appearance of acanthocytes. Elevated tyrosine kinase Lyn activity has been recently identified as one of the key pathophysiological mechanisms in this disease, and therefore represents a promising drug target. Methods: We evaluated an individual off-label treatment with the tyrosine kinase inhibitor dasatinib (100 mg/d, 25.8–50.4 weeks) of three ChAc patients. Alongside thorough safety monitoring, we assessed motor and non-motor scales (e.g., MDS-UPDRS, UHDRS, quality of life) as well as routine and experimental laboratory parameters (e.g., serum neurofilament, Lyn kinase activity, actin cytoskeleton in red blood cells). Results: Dasatinib appeared to be reasonably safe. The clinical parameters remained stable without significant improvement or deterioration. Regain of deep tendon reflexes was observed in one patient. Creatine kinase, serum neurofilament levels, and acanthocyte count did not reveal consistent effects. However, a reduction of initially elevated Lyn kinase activity and accumulated autophagy markers, as well as a partial restoration of the actin cytoskeleton, was found in red blood cells. Conclusions: We report on the first treatment approach with disease-modifying intention in ChAc. The experimental parameters indicate target engagement in red blood cells, while clinical effects on the central nervous system could not be proven within a rather short treatment time. Limited knowledge on the natural history of ChAc and the lack of appropriate biomarkers remain major barriers for “clinical trial readiness”. We suggest a panel of outcome parameters for future clinical trials in ChAc.

Therapeutic targeting of Lyn kinase to treat chorea-acanthocytosis

Chorea-Acanthocytosis (ChAc) is a devastating, little understood, and currently untreatable neurodegenerative disease caused by VPS13A mutations. Based on our recent demonstration that accumulation of activated Lyn tyrosine kinase is a key pathophysiological event in human ChAc cells, we took advantage of Vps13a^−/− mice, which phenocopied human ChAc. Using proteomic approach, we found accumulation of active Lyn, γ-synuclein and phospho-tau proteins in Vps13a^−/− basal ganglia secondary to impaired autophagy leading to neuroinflammation. Mice double knockout Vps13a^−/− Lyn^−/− showed normalization of red cell morphology and improvement of autophagy in basal ganglia. We then in vivo tested pharmacologic inhibitors of Lyn: dasatinib and nilotinib. Dasatinib failed to cross the mouse brain blood barrier (BBB), but the more specific Lyn kinase inhibitor nilotinib, crosses the BBB. Nilotinib ameliorates both Vps13a^−/− hematological and neurological phenotypes, improving autophagy and preventing neuroinflammation. Our data support the proposal to repurpose nilotinib as new therapeutic option for ChAc patients.