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.

Polysomnographic findings in the ultra-rare McLeod syndrome: further documentation of sleep apnea as a possible feature.

STUDY OBJECTIVES: McLeod syndrome is a very rare multisystemic neurodegenerative disease linked to mutations in the XK gene. It has cardiac, neurologic, and neuromuscular manifestations and shares similarities with Huntington's disease. The aim of this study was to evaluate sleep patterns of patients affected by McLeod syndrome. METHODS: This retrospective case series of four males who underwent diagnostic polysomnography (mean age 53.8 ± 2.5 years) includes self-reported and objective evaluation of sleep using the Epworth Sleepiness Scale, genetic tests, documentation of clinical course and features, and laboratory-based full-night attended video-polysomnography. RESULTS: In three out of four patients, an Epworth Sleepiness Scale score ≥ 7 was evident. The average apnea-hypopnea index was 45.0 ± 19.0, with predominantly obstructive phenotype in three patients and predominant central events (central sleep apnea syndrome) in one patient. A significantly increased periodic limb movement index during sleep was observed in all patients. All patients tolerated continuous positive airway pressure or pressure controlled therapy. CONCLUSIONS: Polysomnography of all patients confirmed sleep apnea syndrome as a feature of McLeod syndrome. Three patients were diagnosed with obstructive sleep apnea and one with central sleep apnea syndrome. In addition, periodic limb movement index was increased in all patients. CITATION: Dieter M, Kevin P, Tobias V, et al. Polysomnographic findings in the ultra-rare McLeod syndrome: further documentation of sleep apnea as a possible feature. J Clin Sleep Med. 2024;20(3):339-344.

Proceedings of the Eleventh International Meeting on Neuroacanthocytosis Syndromes.

The 11th International Meeting on Neuroacanthocytosis Syndromes was held on September 15th-17th, 2023 at the University Hospital Campus in Homburg/Saar, Germany. The meeting followed the previous ten international symposia, the last of which was held online due to restrictions due to COVID19, in March 2021. The setting of the meeting encouraged interactions, exchange of ideas, and networking opportunities among the participants from around the globe, including basic and clinical scientists, clinicians, and especially patients, their relatives and caregivers. A total of about 20 oral communications were presented in five scientific sessions accompanied by a keynote lecture, a "Poster-Blitz" session, the "Glenn Irvine Prize" lecture and a panel discussion about "Patient registries, international cooperation & future perspectives". In summary, attendees discussed recent advances and set the basis for the next steps, action points, and future studies in close collaboration with the patient associations, which were actively involved in the whole process.

Novel heterozygous VPS13A pathogenic variants in chorea-neuroacanthocytosis: a case report.

BACKGROUND: Chorea-acanthocytosis (ChAc) is a rare hereditary autosomal recessive neurodegenerative disorder caused by pathogenic variants of the Vacuolar Protein Sorting 13 homolog A (VPS13A) gene. The variant spectrum of VPS13A has not been completely elucidated. This study reports two novel heterozygous VPS13A pathogenic variants in ChAc that expand the variant spectrum of VPS13A. CASE PRESENTATION: We described a case of a 29-year-old man with typical clinical manifestations of ChAc, including chorea, orofacial lingual dyskinesia, vocal tics, elevated serum biochemical indicators, increased acanthocytes in peripheral blood, and caudate nucleus atrophy. Next-generation sequencing revealed two heterozygous variants of VPS13A: a nonsense variant (NM_033305.2: c.8215G > T, p. Glu2739Ter) and a deletion variant in the exons 25-31. CONCLUSION: The identified nonsense variant gives rise to premature translation termination, while the deletion variant is expected to cause a significant in-frame deletion of amino acid residues in the encoded protein. Both variants are considered to be pathogenic and result in loss-of-function proteins. These findings have implications for the genetic counseling of patients with VPS13A variants.

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.

A Case of McLeod's Syndrome Presenting with Severe Decompensated Heart Failure.

McLeod's syndrome (MLS) is an X-linked disorder caused by mutations in the XK gene with neurological manifestations as well as cardiomyopathy. This is a case of acute exacerbation of heart failure in a 44-year-old White male with a confirmed diagnosis of MLS, which was managed with guideline-directed medical therapy and placement of an implantable cardioverter defibrillator with recovery in ejection fraction.

Sphingolipid and Phospholipid Levels Are Altered in Human Brain in Chorea-Acanthocytosis.

BACKGROUND: Chorea-acanthocytosis (ChAc) is associated with mutations of VPS13A, which encodes for chorein, a protein implicated in lipid transport at intracellular membrane contact sites. OBJECTIVES: The goal of this study was to establish the lipidomic profile of patients with ChAc. METHODS: We analyzed 593 lipid species in the caudate nucleus (CN), putamen, and dorsolateral prefrontal cortex (DLPFC) from postmortem tissues of four patients with ChAc and six patients without ChAc. RESULTS: We found increased levels of bis(monoacylglycerol)phosphate, sulfatide, lysophosphatidylserine, and phosphatidylcholine ether in the CN and putamen, but not in the DLPFC, of patients with ChAc. Phosphatidylserine and monoacylglycerol were increased in the CN and N-acyl phosphatidylserine in the putamen. N-acyl serine was decreased in the CN and DLPFC, whereas lysophosphatidylinositol was decreased in the DLPFC. CONCLUSIONS: We present the first evidence of altered sphingolipid and phospholipid levels in the brains of patients with ChAc. Our observations are congruent with recent findings in cellular and animal models, and implicate defects of lipid processing in VPS13A disease pathophysiology. © 2023 International Parkinson and Movement Disorder Society. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Effect of rapamycin on lysosomal accumulation in a CRISPR/Cas9-based cellular model of VPS13A deficiency.

VPS13A is a lipid transfer protein localized at different membrane contact sites between organelles, and mutations in the corresponding gene produce a rare neurodegenerative disease called chorea-acanthocytosis (ChAc). Previous studies showed that VPS13A depletion in HeLa cells results in an accumulation of endosomal and lysosomal markers, suggesting a defect in lysosomal degradation capacity leading to partial autophagic dysfunction. Our goal was to determine whether compounds that modulate the endo-lysosomal pathway could be beneficial in the treatment of ChAc. To test this hypothesis, we first generated a KO model using CRISPR/Cas9 to study the consequences of the absence of VPS13A in HeLa cells. We found that inactivation of VPS13A impairs cell growth, which precludes the use of isolated clones due to the undesirable selection of edited clones with residual protein expression. Therefore, we optimized the use of pool cells obtained shortly after transfection with CRISPR/Cas9 components. These cells are a mixture of wild-type and edited cells that allow a comparative analysis of phenotypes and avoids the selection of clones with residual level of VPS13A expression after long-term growth. Consistent with previous observations by siRNA inactivation, VPS13A inactivation by CRISPR/Cas9 resulted in accumulation of the endo-lysosomal markers RAB7A and LAMP1. Notably, we observed that rapamycin partially suppressed the difference in lysosome accumulation between VPS13A KO and WT cells, suggesting that modulation of the autophagic and lysosomal pathway could be a therapeutic target in the treatment of ChAc.

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.

How we approach transfusions in a patient with high risk of alloimmunization from McLeod phenotype.

McLeod phenotype-caused by the missing Xk protein-is a very rare red cell phenotype, one characteristic of McLeod syndrome, and sometimes associated with X-linked chronic granulomatous disease (CGD). Diagnosis of McLeod phenotype is important for appropriate transfusion management, because red blood cells from all healthy donors will have the Xk protein with its Kx antigen and can lead to red cell antibody formation without the ability to find compatible McLeod phenotype blood for transfusion. We offer a review and approach to diagnosis of the McLeod phenotype and special transfusion considerations.

Endosomal recycling defects link Huntington's disease with McLeod syndrome.

Chhetri and colleagues (2022. J. Cell Biol.https://doi.org/10.1083/jcb.202112073) show that Rab11-mediated endosomal recycling regulates cell surface expression of McLeod syndrome protein XK. Mutant huntingtin interferes with the recycling of XK to the cell surface and significantly reduces manganese transport across cell membrane.

Chronic granulomatous disease and McLeod syndrome: Stem cell transplant and transfusion support in a 2-year-old patient-a case report.

Chronic granulomatous disease (CGD) with McLeod neuroacanthocytosis syndrome (MLS) is a contiguous gene deletion disorder characterized by defective phagocytic function and decreased Kell antigen expression. CGD cure is achieved through hematopoietic stem cell transplant (HSCT) usually in the peri-pubescent years. The presence of MLS makes peri-transfusion support complex, however. Herein, we present the youngest known case of HSCT for CGD in the setting of MLS. A 2-year-old male patient was diagnosed with CGD plus MLS. Due to the severity of the child's systemic fungal infection at diagnosis, HSCT was deemed the best treatment option despite his small size and age. A related, matched donor was available, and a unique red blood cell support plan had been implemented. Reduced-intensity conditioning was used to reduce the transplant-related mortality risk associated with myeloablative protocols. The transplant course was uneventful; autologous red blood cell (RBC) transfusion support was successful and allowed for the avoidance of possible antibody formation if allogeneic units had been used. The patient achieved 1-year relapse-free survival. The developed protocols provide a viable path to transplant in the very young, and early transplant to cure could reduce disease-related morbidity.

Clinical and Molecular Findings of Intermediate Allele Carriers in the HTT Gene from the Mexican Mestizo Population.

INTRODUCTION: There are reports of different clinical statuses in carriers of intermediate alleles (IAs) of CAG trinucleotide repeats in the HTT gene, from individuals affected by a clinical picture indistinguishable from Huntington's disease (HD) to those without manifestations. Therefore, the possible clinical significance of these alleles has been widely debated. OBJECTIVES: The aim of this study was to describe general and clinical features and discard HD phenocopies by molecular assessment in a case series of IA carriers on the HTT gene of a laboratory sample from a neurological center in Mexico. METHODS: We selected individuals who had previously been tested for the HTT gene expansion, which resulted in IAs. Clinical information was obtained from medical records, and molecular analysis of the JPH3, PRNP, and TBP genes was performed only in IA carriers with clinical manifestations. In addition, two patients with IA and acanthocytes were evaluated by whole-exome sequencing. The scientific and ethical committees of the National Institute of Neurology and Neurosurgery Manuel Velasco Suárez (NINNMVS) approved this study. RESULTS: From 1994 to 2019, the Genetics Department of the NINNMVS confirmed 34 individuals with IAs, 15 of whom belonged to 11 families with HD (IA-HD) and 19 of whom had no family history of HD (IA-non-HD). We found a high proportion of manifestations of the HD phenotypic spectrum in the IA-non-HD subgroup. In addition, among the 20 samples of IA carriers with manifestations molecularly evaluated, we identified two unrelated subjects with CAG/CTG repeat expansions on the JPH3 gene, confirming HD-like 2 (HDL2), and one patient with the homozygous pathogenic c.3232G>T variant (p.Glu1078Ter) in the VPS13A gene, demonstrating choreoacanthocytosis. DISCUSSION/CONCLUSION: Our results show the most extensive series of subjects with IAs and clinical manifestations. In addition, we identify three HD phenocopies, two HDL2 cases, and one choreoacanthocytosis case. Therefore, we emphasize evaluating other HD phenocopies in IA carriers with clinical manifestations whose family background is not associated with HD.

Interaction between VPS13A and the XK scramblase is important for VPS13A function in humans.

VPS13 family proteins form conduits between the membranes of different organelles through which lipids are transferred. In humans, there are four VPS13 paralogs, and mutations in the genes encoding each of them are associated with different inherited disorders. VPS13 proteins contain multiple conserved domains. The Vps13 adaptor-binding (VAB) domain binds to adaptor proteins that recruit VPS13 to specific membrane contact sites. This work demonstrates the importance of a different domain in VPS13A function. The pleckstrin homology (PH) domain at the C-terminal region of VPS13A is required to form a complex with the XK scramblase and for the co-localization of VPS13A with XK within the cell. Alphafold modeling was used to predict an interaction surface between VPS13A and XK. Mutations in this region disrupt both complex formation and co-localization of the two proteins. Mutant VPS13A alleles found in patients with VPS13A disease truncate the PH domain. The phenotypic similarities between VPS13A disease and McLeod syndrome caused by mutations in VPS13A and XK, respectively, argue that loss of the VPS13A-XK complex is the basis of both diseases.

A partnership between the lipid scramblase XK and the lipid transfer protein VPS13A at the plasma membrane.

Chorea-acanthocytosis (ChAc) and McLeod syndrome are diseases with shared clinical manifestations caused by mutations in VPS13A and XK, respectively. Key features of these conditions are the degeneration of caudate neurons and the presence of abnormally shaped erythrocytes. XK belongs to a family of plasma membrane (PM) lipid scramblases whose action results in exposure of PtdSer at the cell surface. VPS13A is an endoplasmic reticulum (ER)-anchored lipid transfer protein with a putative role in the transport of lipids at contacts of the ER with other membranes. Recently VPS13A and XK were reported to interact by still unknown mechanisms. So far, however, there is no evidence for a colocalization of the two proteins at contacts of the ER with the PM, where XK resides, as VPS13A was shown to be localized at contacts between the ER and either mitochondria or lipid droplets. Here we show that VPS13A can also localize at ER-PM contacts via the binding of its PH domain to a cytosolic loop of XK, that such interaction is regulated by an intramolecular interaction within XK, and that both VPS13A and XK are highly expressed in the caudate neurons. Binding of the PH domain of VPS13A to XK is competitive with its binding to intracellular membranes that mediate other tethering functions of VPS13A. Our findings support a model according to which VPS13A-dependent lipid transfer between the ER and the PM is coupled to lipid scrambling within the PM. They raise the possibility that defective cell surface exposure of PtdSer may be responsible for neurodegeneration.

Yeast as a Model to Find New Drugs and Drug Targets for VPS13-Dependent Neurodegenerative Diseases.

Mutations in human VPS13A-D genes result in rare neurological diseases, including chorea-acanthocytosis. The pathogenesis of these diseases is poorly understood, and no effective treatment is available. As VPS13 genes are evolutionarily conserved, the effects of the pathogenic mutations could be studied in model organisms, including yeast, where one VPS13 gene is present. In this review, we summarize advancements obtained using yeast. In recent studies, vps13Δ and vps13-I2749 yeast mutants, which are models of chorea-acanthocytosis, were used to screen for multicopy and chemical suppressors. Two of the suppressors, a fragment of the MYO3 and RCN2 genes, act by downregulating calcineurin activity. In addition, vps13Δ suppression was achieved by using calcineurin inhibitors. The other group of multicopy suppressors were genes: FET4, encoding iron transporter, and CTR1, CTR3 and CCC2, encoding copper transporters. Mechanisms of their suppression rely on causing an increase in the intracellular iron content. Moreover, among the identified chemical suppressors were copper ionophores, which require a functional iron uptake system for activity, and flavonoids, which bind iron. These findings point at areas for further investigation in a higher eukaryotic model of VPS13-related diseases and to new therapeutic targets: calcium signalling and copper and iron homeostasis. Furthermore, the identified drugs are interesting candidates for drug repurposing for these diseases.

McLeod syndrome with a novel XK frameshift mutation: A case report.

RATIONALE: McLeod syndrome (MLS) is a rare X-linked neurohematologic disorder caused by loss-of-function mutations in the XK gene. However, variations in the XK gene remain to be elucidated. Here, we report the clinical phenotype and genetic features of a patient with MLS caused by a novel frameshift mutation in the XK gene. PATIENT CONCERNS: A 44-year-old man presented with chorea, cognitive impairment, mental disorders, and seizures accompanied by peripheral neuropathy, hyperCKemia, and acanthocytosis. The proband's mother had a mild chorea. One older brother who died 10 years ago without a confirmed diagnosis showed symptoms of both chorea and mental disorders, while the other brother also developed mild chorea. DIAGNOSIS: The patient was diagnosed with MLS based on the family history, clinical manifestations, and accessory examinations. Whole-exome sequencing studies revealed a novel frameshift mutation resulting from a nucleotide variation in exon 2 (452delA) that leads to an amino acid residue conversion from Gln to Arg and early termination of the XK protein (Gln151ArgfsTer2). The patient and one of his older brothers were hemizygotes, and his mother was heterozygous. INTERVENTIONS: The patient was treated with haloperidol to control chorea and levetiracetam to control seizures. OUTCOMES: Six months after treatment, the proband was seizure-free, but showed little improvement in chorea and cognitive dysfunction. LESSON: We describe a family with MLS caused by a novel frameshift mutation in the XK gene. The causes of the mild clinical presentation in the proband's mother require further investigation.