Physiological and Pathogenesis Significance of Chorein in Health and Disease.

This comprehensive review explores the physiological and pathophysiological significance of VPS13A, a protein encoded by the VPS13A gene. The VPS13A gene is associated with Chorea-acanthocytosis (ChAc), a rare hereditary neurodegenerative disorder. The review covers essential aspects, beginning with the genetics of VPS13A, highlighting its role in the pathogenesis of ChAc, and addressing the spectrum of genetic variants involved. It delves into the structure and function of the VPS13A protein, emphasizing its presence in various tissues and its potential involvement in protein trafficking and lipid homeostasis. Molecular functions of VPS13A in the brain tissue and other cell types or tissues with respect to their role in cytoskeletal regulation and autophagy are explored. Finally, it explores the intriguing link between VPS13A mutations, lipid imbalances, and neurodegeneration, shedding light on future research directions. Overall, this review serves as a comprehensive resource for understanding the pivotal role of VPS13A in health and disease, particularly in the context of ChAc. Key words: Chorein , Tumor, Actin, Microfilament, Gene expression, Chorea-acanthocytosis.

Identification of four novel mutations in VSP13A in Iranian patients with Chorea-acanthocytosis (ChAc).

Chorea-acanthocytosis (ChAc) is a rare autosomal recessive neurodegenerative disorder characterized by a variety of involuntary movements, predominantly chorea, and the presence of acanthocytosis in peripheral blood smears. ChAc is caused by mutations in the vacuolar protein sorting-associated protein 13A (VPS13A) gene. The aim of the present study was to conduct a clinical and genetic analysis of five patients with suspected ChAc in Iran. This study included five patients who were referred to the genetic department of the Endocrinology and Metabolism Research Institute between 2020 and 2022, with a suspicion of ChAc. Clinical features and the presence of characteristic MRI findings were evaluated in the patients. Whole-exome sequencing (WES) followed by Sanger sequencing was employed to identify the disease-causing variants. The functional effects of novel mutations were analyzed by specific bioinformatics prediction tools. WES and data analysis revealed the presence of five distinct VPS13A mutations in the patients, four of which were novel. These included one nonsense mutation (p.L984X), and three splice site mutations (c.755-1G>A, c.144+1 G>C, c.2512+1G>A). All mutations were validated by Sanger sequencing, and in silico analysis predicted that all mutations were pathogenic. This study provides the first molecular genetic characteristics of Iranian patients with ChAc, identifying four novel mutations in the VPS13A gene. These findings expand the VPS13A variants spectrum and confirm the clinical variability in ChAc patients.

Multisystem pathology in McLeod syndrome.

We present a comprehensive characterization of clinical, neuropathological, and multisystem features of a man with genetically confirmed McLeod neuroacanthocytosis syndrome, including video and autopsy findings. A 61-year-old man presented with a movement disorder and behavioral change. Examination showed dystonic choreiform movements in all four limbs, reduced deep-tendon reflexes, and wide-based gait. He had oromandibular dyskinesia causing severe dysphagia. Elevated serum creatinine kinase (CK) was first noted in his thirties, but investigations, including muscle biopsy at that time, were inconclusive. Brain magnetic resonance imaging showed white matter volume loss, atrophic basal ganglia, and chronic small vessel ischemia. Despite raised CK, electromyography did not show myopathic changes. Exome gene panel testing was negative, but targeted genetic analysis revealed a hemizygous pathogenic variant in the XK gene c.895C > T p.(Gln299Ter), consistent with a diagnosis of McLeod syndrome. The patient died of sepsis, and autopsy showed astrocytic gliosis and atrophy of the basal ganglia, diffuse iron deposition in the putamen, and mild Alzheimer's pathology. Muscle pathology was indicative of mild chronic neurogenic atrophy without overt myopathic features. He had non-specific cardiomyopathy and splenomegaly. McLeod syndrome is an ultra-rare neurodegenerative disorder caused by X-linked recessive mutations in the XK gene. Diagnosis has management implications since patients are at risk of severe transfusion reactions and cardiac complications. When a clinical diagnosis is suspected, candidate genes should be interrogated rather than solely relying on exome panels.

A chorea-acanthocytosis patient with novel mutations in the VPS13A gene without acanthocyte.

Chorea-acanthocytosis (ChAc) is a rare clinical genetic disorder of the nervous system, which is characterized by choreiform movement disorder, cognitive decline, and psychiatric disorders. ChAc is mostly diagnosed based on its typical clinical manifestations and the increased number of acanthocytes in peripheral blood smears. Here, we report a patient, who has the characteristic clinical manifestations of ChAc with limb choreiform movements, involuntary lip and tongue bites, seizures, and emotional instability. However, her blood smear was negative for acanthocytes with scanning electron microscopy. We later identified two novel pathogenic mutations in the patient's vacuolar protein sorting homolog 13 A (VPS13A) on chromosome 9q21 by targeted gene sequencing, and she was definitively diagnosed with "ChAc." After treatment with carbamazepine, haloperidol, the patient's symptoms gradually improved. We consider that an acanthocyte negative blood smear cannot rule out ChAC diagnosis, and genetic testing is the "gold standard" for the diagnosis. Through a review of previous research, it is rare for a patient to have a clear diagnosis of ChAc by genetic testing, but whose blood smear is negative for acanthocytes with electron microscopy. In addition, in this report, we discovered two novel pathogenic mutations, which have not been reported previously, and extended the genetic characteristics of ChAc.

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.

Exome sequencing of choreoacanthocytosis reveals novel mutations in VPS13A and co-mutation in modifier gene(s).

Choreoacanthocytosis, one of the forms of neuroacanthocytosis, is caused by mutations in vacuolar protein sorting-associated protein A (VPS13A), and is often misdiagnosed with other form of neuroacanthocytosis with discrete genetic defects. The phenotypic variations among the patients with VPS13A mutations significantly obfuscates the understanding of the disease and treatment strategies. In this study, two unrelated cases were identified, exhibiting the core phenotype of neuroacanthocytosis but with considerable clinical heterogeneity. Case 1 presented with an additional Parkinsonism phenotype, whereas seizures were evident in case 2. To decipher the genetic basis, whole exome sequencing followed by validation with Sanger sequencing was performed. A known homozygous pathogenic nonsense mutation (c.799C > T; p.R267X) in exon 11 of the VPS13A gene was identified in case 1 that resulted in a truncated protein. A novel missense mutation (c.9263T > G; p.M3088R) in exon 69 of VPS13A identified in case 2 was predicted as pathogenic. In silico analysis of the p.M3088R mutation at the C-terminus of VPS13A suggests a loss of interaction with TOMM40 and may disrupt mitochondrial localization. We also observed an increase in mitochondrial DNA copy numbers in case 2. Mutation analysis revealed benign heterozygous variants in interacting partners of VPS13A such as VAPA in case 1. Our study confirmed the cases as ChAc and identified the novel homozygous variant of VPS13A (c.9263T > G; p.M3088R) within the mutation spectrum of VPS13A-associated ChAc. Furthermore, mutations in VPS13A and co-mutations in its potential interacting partner(s) might contribute to the diverse clinical manifestations of ChAc, which requires further study.

Acupuncture for treating symptoms associated with chorea-acanthocytosis: A CARE-compliant case report.

BACKGROUND: Chorea-acanthocytosis (ChAc) is the most common type of neuroacanthocytosis syndromes. Characteristic movement disorders of ChAc are choreiform movements affecting both trunk and extremities. Acanthocytosis in peripheral blood smear, elevated serum creatine kinase, atrophy of heads of caudate nuclei and dilation of the anterior horn of the lateral ventricles in magnetic resonance imaging could assist the diagnosis of ChAc. OBJECTIVE: We aimed to report on the use of acupuncture to successfully improve ChAc symptoms. METHOD: A patient with definite ChAc was admitted, who had suffered from involuntary tongue protrusion for about 10 years. Acupuncture treatment was administrated for 3 times a week for 2 months. The chorea tremor control area, Baihui (GV20), Sishencong (EX-HN1), Shenting (GV24), Benshen (GB13, bilateral), Yintang (GV29), Neiguan (PC6, bilateral), Tongli (HT5, bilateral), Zusanli (ST36, bilateral), Sanyinjiao (SP6, bilateral), Dicang (ST4, bilateral), Chengjiang (CV24), Lianquan (CV23), Jinjin (EX-HN12) and Yuye (EX-HN13) were selected as acupunture points. RESULTS: Previous drug dosage was reduced and the frequency of involuntary tongue protrusion was significantly reduced. Other clinical symptoms were also well controlled. Peripheral blood smear still indicated an increased proportion of red lineage, but blood analyses revealed improvement at follow-up. CONCLUSIONS: For patients who do not response well to conventional medical treatments, acupuncture might be used as an alternative treatment for symptoms related to ChAc.

The Erythrocyte Sedimentation Rate and Its Relation to Cell Shape and Rigidity of Red Blood Cells from Chorea-Acanthocytosis Patients in an Off-Label Treatment with Dasatinib.

BACKGROUND: Chorea-acanthocytosis (ChAc) is a rare hereditary neurodegenerative disease with deformed red blood cells (RBCs), so-called acanthocytes, as a typical marker of the disease. Erythrocyte sedimentation rate (ESR) was recently proposed as a diagnostic biomarker. To date, there is no treatment option for affected patients, but promising therapy candidates, such as dasatinib, a Lyn-kinase inhibitor, have been identified. METHODS: RBCs of two ChAc patients during and after dasatinib treatment were characterized by the ESR, clinical hematology parameters and the 3D shape classification in stasis based on an artificial neural network. Furthermore, mathematical modeling was performed to understand the contribution of cell morphology and cell rigidity to the ESR. Microfluidic measurements were used to compare the RBC rigidity between ChAc patients and healthy controls. RESULTS: The mechano-morphological characterization of RBCs from two ChAc patients in an off-label treatment with dasatinib revealed differences in the ESR and the acanthocyte count during and after the treatment period, which could not directly be related to each other. Clinical hematology parameters were in the normal range. Mathematical modeling indicated that RBC rigidity is more important for delayed ESR than cell shape. Microfluidic experiments confirmed a higher rigidity in the normocytes of ChAc patients compared to healthy controls. CONCLUSIONS: The results increase our understanding of the role of acanthocytes and their associated properties in the ESR, but the data are too sparse to answer the question of whether the ESR is a suitable biomarker for treatment success, whereas a correlation between hematological and neuronal phenotype is still subject to verification.

Neuroacanthocytosis Syndromes in an Italian Cohort: Clinical Spectrum, High Genetic Variability and Muscle Involvement.

Neuroacanthocytosis (NA) syndromes are a group of genetically defined diseases characterized by the association of red blood cell acanthocytosis, progressive degeneration of the basal ganglia and neuromuscular features with characteristic persistent hyperCKemia. The main NA syndromes include autosomal recessive chorea-acanthocytosis (ChAc) and X-linked McLeod syndrome (MLS). A series of Italian patients selected through a multicenter study for these specific neurological phenotypes underwent DNA sequencing of the VPS13A and XK genes to search for causative mutations. Where it has been possible, muscle biopsies were obtained and thoroughly investigated with histochemical assays. A total of nine patients from five different families were diagnosed with ChAC and had mostly biallelic changes in the VPS13A gene (three nonsense, two frameshift, three splicing), while three patients from a single X-linked family were diagnosed with McLeod syndrome and had a deletion in the XK gene. Despite a very low incidence (only one thousand cases of ChAc and a few hundred MLS cases reported worldwide), none of the 8 VPS13A variants identified in our patients is shared by two families, suggesting the high genetic variability of ChAc in the Italian population. In our series, in line with epidemiological data, McLeod syndrome occurs less frequently than ChAc, although it can be easily suspected because of its X-linked mode of inheritance. Finally, histochemical studies strongly suggest that muscle pathology is not simply secondary to the axonal neuropathy, frequently seen in these patients, but primary myopathic alterations can be detected in both NA syndromes.

Decreased Na+/K+ ATPase Expression and Depolarized Cell Membrane in Neurons Differentiated from Chorea-Acanthocytosis Patients.

Loss of function mutations of the chorein-encoding gene VPS13A lead to chorea-acanthocytosis (ChAc), a neurodegenerative disorder with accelerated suicidal neuronal cell death, which could be reversed by lithium. Chorein upregulates the serum and glucocorticoid inducible kinase SGK1. Targets of SGK1 include the Na+/K+-ATPase, a pump required for cell survival. To explore whether chorein-deficiency affects Na+/K+ pump capacity, cortical neurons were differentiated from iPSCs generated from fibroblasts of ChAc patients and healthy volunteers. Na+/K+ pump capacity was estimated from K+-induced whole cell outward current (pump capacity). As a result, the pump capacity was completely abolished in the presence of Na+/K+ pump-inhibitor ouabain (100 µM), was significantly smaller in ChAc neurons than in control neurons, and was significantly increased in ChAc neurons by lithium treatment (24 hours 2 mM). The effect of lithium was reversed by SGK1-inhibitor GSK650394 (24 h 10 µM). Transmembrane potential (Vm) was significantly less negative in ChAc neurons than in control neurons, and was significantly increased in ChAc neurons by lithium treatment (2 mM, 24 hours). The effect of lithium on Vm was virtually abrogated by ouabain. Na+/K+ α1-subunit transcript levels and protein abundance were significantly lower in ChAc neurons than in control neurons, an effect reversed by lithium treatment (2 mM, 24 hours). In conclusion, consequences of chorein deficiency in ChAc include impaired Na+/K+ pump capacity.

The binding of the APT1 domains to phosphoinositides is regulated by metal ions in vitro.

Chorein is a protein of the Vps13 family, and defects in this protein cause the rare neurodegenerative disorder chorea-acanthocytosis (ChAc). Chorein is involved in the actin cytoskeleton organization, calcium ion flux, neuronal cell excitability, exocytosis and autophagy. The function of this protein is poorly understood, and obtaining this knowledge is a key to finding a cure for ChAc. Chorein, as well as the Vps13 protein from yeast, contains the APT1 domain. Our previous research has shown that the APT1 domain from yeast Vps13 (yAPT1v) binds phosphatidylinositol 3-phosphate (PI3P) in vitro. In this study, we showed that although the APT1 domain from chorein (hAPT1) binds to PI3P it could not functionally replace yAPT1v. The hAPT1 domain binds, in addition to PI3P, to phosphatidylinositol 5-phosphate (PI5P). The binding of hAPT1 to PI3P, unlike the binding of yAPT1v to PI3P, is regulated by the bivalent ions, calcium and magnesium. Regulation of PI3P binding via calcium is also observed for the APT1 domain of yeast autophagy protein Atg2. The substitution I2771R, found in chorein of patient suffering from ChAc, reduces the binding of the hAPT1 domain to PI3P and PI5P. These results suggest that the ability of APT1 domains to bind phosphoinositides is regulated differently in yeast and human protein and that this regulation is important for chorein function.

Novel pathogenic VPS13A mutation in Moroccan family with Choreoacanthocytosis: a case report.

BACKGROUND: Choreoacanthocytosis (ChAc), is a rare neurodegenerative disease, characterized by movement disorders and acanthocytosis in the peripheral blood smears, and various neurological, neuropsychiatric and neuromuscular signs. It is caused by mutations in VPS13A gene with autosomal recessive pattern of inheritance. CASE PRESENTATION: Here we report two patients belonging to a consanguineous Moroccan family who present with movement disorder pathology. They were suspected to have choreoacanthocytosis according to biological, clinical and radiological finding. Thus, whole-exome sequencing was performed for precise diagnosis and identified a homozygous novel nonsense mutation c.337C > T (p.Gln113*) in exon 5 of VPS13A in the two affected siblings. CONCLUSION: Here, we report a novel nonsense p.Gln113* mutation in VPS13A identified by whole-exome sequencing, which caused ChAc in a Moroccan family. This is the first description of ChAc in Morocco with genetic confirmation, that expands the mutation diversity of VPS13A and provide clinical, neuroimaging and deep brain stimulation findings.

Neuroacanthocytosis: a case report of chorea-acanthocytosis.

Neuroacanthocytosis is a rare progressive neurodegenerative disease, including Chorea-acanthocytosis, McLeod syndrome, Huntington's disease-like 2, and pantothenate kinase-associated neurodegeneration, where Chorea-acanthocytosis occupies the main entity of this disease group. Here, a classic case of Chorea-acanthocytosis is reported that exhibited gradually deteriorating abnormal movements of limbs and face, swallowing difficulty, and lip and cheek biting for the past two years. Peripheral blood smears revealed that 35% of the red blood cells were acanthocytes and electron microcopy scans clearly showed the morphology of acanthocytes. VPS13A gene sequencing found a heterozygous novel VPS13A gene mutation (c.80dupT). Brain magnetic resonance imaging scans showed moderate anterior horn dilation of lateral ventricles and bilateral atrophy of the head of caudate nucleus. Several suggestive features are summarized to provide diagnostic clues for Chorea-acanthocytosis and facilitate future diagnosis and treatment.

Neuroacanthocytosis with unusual clinical features: A case report.

RATIONALE: Neuroacanthocytosis (NA) is a heterogeneous group of inherited neurodegenerative disorders characterized by misshapen spiculated erythorcytes and symptoms that resemble Huntington's disease. PATIENT CONCERNS: A 59-year-old female who developed hyperkinetic involuntary movements that became progressively more obvious during the course of a year. DIAGNOSES: Acanthocytes were observed in a peripheral blood smear. The patient had elevated levels of serum creatine kinase (CK). Gene sequencing did not reveal a genetic mutation. INTERVENTIONS: The patient was administered oral tiapride, alprazolam, B1 and B12 Vitamins. OUTCOMES: After 2 months of treatment the patient's symptoms were obviously alleviated. At the 6 month follow-up, the patient could feed herself and walk without assistance. LESSONS: The NA syndrome is extremely rare. It may be identified in the clinic based on abnormal orofacial movement, chorea, cognitive decline, elevated CK levels, and acanthocytosis. If available, protein- or genetic-based testing may provide a confirmatory diagnosis.

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

AIMS: Quantitative estimation of cortical neurone loss in cases with chorea-acanthocytosis (ChAc) and its impact on laminar composition. METHODS: We used unbiased stereological tools to estimate the degree of cortical pathology in serial gallocyanin-stained brain sections through the complete hemispheres of three subjects with genetically verified ChAc and a range of disease durations. We compared these results with our previous data of five Huntington's disease (HD) and five control cases. Pathoarchitectonic changes were exemplarily documented in TE1 of a 61-year-old female HD-, a 60-year-old female control case, and ChAc3. RESULTS: Macroscopically, the cortical volume of our ChAc cases (ChAc1-3) remained close to normal. However, the average number of neurones was reduced by 46% in ChAc and by 33% in HD (P = 0.03 for ChAc & HD vs. controls; P = 0.64 for ChAc vs. HD). Terminal HD cases featured selective laminar neurone loss with pallor of layers III, V and VIa, a high density of small, pale, closely packed radial fibres in deep cortical layers VI and V, shrinkage, and chromophilia of subcortical white matter. In ChAc, pronounced diffuse astrogliosis blurred the laminar borders, thus masking the complete and partial loss of pyramidal cells in layer IIIc and of neurones in layers III, V and VI. CONCLUSION: ChAc is a neurodegenerative disease with distinct cortical neurodegeneration. The hypertrophy of the peripheral neuropil space of minicolumns with coarse vertical striation was characteristic of ChAc. The role of astroglia in the pathogenesis of this disorder remains to be elucidated.

Defective mitochondrial and lysosomal trafficking in chorea-acanthocytosis is independent of Src-kinase signaling.

Mutations in the VPS13A gene leading to depletion of chorein protein are causative for Chorea Acanthocytosis (ChAc), a rare devastating disease, which is characterized by neurodegeneration mainly affecting the basal ganglia as well as deformation of erythrocytes. Studies on patient blood samples highlighted a dysregulation of Actin cytoskeleton caused by downregulation of the PI3K pathway and hyper-activation of Lyn-kinase, but to what extent these mechanisms are present and relevant in the affected neurons remains elusive. We studied the effects of the absence of chorein protein on the morphology and trafficking of lysosomal and mitochondrial compartments in ChAc patient-specific induced pluripotent stem cell-derived medium spiny neurons (MSNs). Numbers of both organelle types were reduced in ChAc MSNs. Mitochondrial length was shortened and their membrane potential showed significant hyperpolarization. In contrast to previous studies, showing Lyn kinase dependency of ChAc-associated pathological events in erythrocytes, pharmacological studies demonstrate that the impairment of mitochondria and lysosomes are independent of Lyn kinase activity. These data suggest that impairment in mitochondrial and lysosomal morphologies in MSNs is not mediated by a dysregulation of Lyn kinase and thus the pathological pathways in ChAc might be - at least in part - cell-type specific.

Subcortical neurodegeneration in chorea: Similarities and differences between chorea-acanthocytosis and Huntington's disease.

INTRODUCTION: Chorea-acanthocytosis (ChAc) and Huntington's disease (HD) are neurodegenerative conditions that share clinical and neuropathological features, despite their distinct genetic etiologies. METHODS: In order to compare these neuropathologies, serial gallocyanin-stained brain sections from three subjects with ChAc were analyzed and compared with our previous studies of eight HD cases, in addition to three hemispheres from two male controls. RESULTS: Astrogliosis was much greater in the ChAc striatum, as compared to that found in HD, with dramatic increase in total striatal glia numbers and the number of glia per striatal neuron. Striatal astrocytes are most likely derived from the striatal subependymal layer in ChAc, which showed massive proliferation. The thalamic centromedian-parafascicular complex is reciprocally connected to the striatum and is more heavily affected in HD than in ChAc. CONCLUSION: The distinct patterns of selective vulnerability and gliosis observed in HD and ChAc challenge simplistic views on the pathogenesis of these two diseases with rather similar clinical signs. The particular roles played by astroglia in ChAc and in HD clearly need to be elucidated in more detail.

Lithium Sensitivity of Store Operated Ca2+ Entry and Survival of Fibroblasts Isolated from Chorea-Acanthocytosis Patients.

BACKGROUND: The widely expressed protein chorein fosters activation of the phosphoinositide 3 kinase (PI3K) pathway thus supporting cell survival. Loss of function mutations of the chorein encoding gene VPS13A (vacuolar protein sorting-associated protein 13A) causes chorea-acanthocytosis (ChAc), a neurodegenerative disorder paralleled by deformations of erythrocytes. In mice, genetic knockout of chorein leads to enhanced neuronal apoptosis. PI3K dependent signalling upregulates Orai1, a pore forming channel protein accomplishing store operated Ca2+ entry (SOCE). Increased Orai1 expression and SOCE have been shown to confer survival of tumor cells. SOCE could be up-regulated by lithium. The present study explored, whether SOCE and/or apoptosis are altered in ChAc fibroblasts and could be modified by lithium treatment. METHODS: Fibroblasts were isolated from ChAc patients and age-matched healthy volunteers. Cytosolic Ca2+ activity ([Ca2+]i) was estimated from Fura-2-fluorescence, SOCE from increase of [Ca2+]i following Ca2+ re-addition after Ca2+-store depletion with sarcoendoplasmatic Ca2+-ATPase (SERCA) inhibitor thapsigargin (1 µM), and apoptosis from annexin-V/propidium iodide staining quantified in flow cytometry. RESULTS: SOCE was significantly smaller in ChAc fibroblasts than in control fibroblasts. Lithium (2 mM, 24 hours) significantly increased and Orai1 blocker 2-Aminoethoxydiphenyl Borate (2-APB, 50 µM, 24 hours) significantly decreased SOCE. Annexin-V-binding and propidium iodide staining were significantly higher in ChAc fibroblasts than in control fibroblasts. In ChAc fibroblasts annexin-V-binding and propidium iodide staining were significantly decreased by lithium treatment, significantly increased by 2-APB and virtually lithium insensitive in the presence of 2-APB. CONCLUSIONS: In ChAc fibroblasts, downregulation of SOCE contributes to enhanced susceptibility to apoptosis. Both, decreased SOCE and enhanced apoptosis of ChAc fibroblasts can be reversed by lithium treatment.

Yeast and other lower eukaryotic organisms for studies of Vps13 proteins in health and disease.

Human Vps13 proteins are associated with several diseases, including the neurodegenerative disorder Chorea-acanthocytosis (ChAc), yet the biology of these proteins is still poorly understood. Studies in Saccharomyces cerevisiae, Dictyostelium discoideum, Tetrahymena thermophila and Drosophila melanogaster point to the involvement of Vps13 in cytoskeleton organization, vesicular trafficking, autophagy, phagocytosis, endocytosis, proteostasis, sporulation and mitochondrial functioning. Recent findings show that yeast Vps13 binds to phosphatidylinositol lipids via 4 different regions and functions at membrane contact sites, enlarging the list of Vps13 functions. This review describes the great potential of simple eukaryotes to decipher disease mechanisms in higher organisms and highlights novel insights into the pathological role of Vps13 towards ChAc.

Lithium Sensitive ORAI1 Expression, Store Operated Ca2+ Entry and Suicidal Death of Neurons in Chorea-Acanthocytosis.

Chorea-Acanthocytosis (ChAc), a neurodegenerative disorder, results from loss-of-function-mutations of chorein-encoding gene VPS13A. In tumour cells chorein up-regulates ORAI1, a Ca2+-channel accomplishing store operated Ca2+-entry (SOCE) upon stimulation by STIM1. Furthermore SOCE could be up-regulated by lithium. The present study explored whether SOCE impacts on neuron apoptosis. Cortical neurons were differentiated from induced pluripotent stem cells generated from fibroblasts of ChAc patients and healthy volunteers. ORAI1 and STIM1 transcript levels and protein abundance were estimated from qRT-PCR and Western blotting, respectively, cytosolic Ca2+-activity ([Ca2+]i) from Fura-2-fluorescence, as well as apoptosis from annexin-V-binding and propidium-iodide uptake determined by flow cytometry. As a result, ORAI1 and STIM1 transcript levels and protein abundance and SOCE were significantly smaller and the percentage apoptotic cells significantly higher in ChAc neurons than in control neurons. Lithium treatment (2 mM, 24 hours) increased significantly ORAI1 and STIM1 transcript levels and protein abundance, an effect reversed by inhibition of Serum & Glucocorticoid inducible Kinase 1. ORAI1 blocker 2-APB (50 µM, 24 hours) significantly decreased SOCE, markedly increased apoptosis and abrogated the anti-apoptotic effect of lithium. In conclusion, enhanced neuronal apoptosis in ChAc at least partially results from decreased ORAI1 expression and SOCE, which could be reversed by lithium treatment.