VPS13 Forum Proceedings: XK, XK-Related and VPS13 Proteins in Membrane Lipid Dynamics

Phosphatidylethanolamines are the Main Lipid Class Altered in Red Blood Cells from Patients with VPS13A Disease/Chorea-Acanthocytosis

BACKGROUND

VPS13A disease is an ultra-rare disorder caused by loss of function mutations in VPS13A characterized by striatal degeneration and by red blood cell (RBC) acanthocytosis. VPS13A is a bridge-like protein mediating lipid transfer at membrane contact sites.

OBJECTIVES

To assess the lipid composition of patient-derived RBCs.

METHODS

RBCs collected from 5 VPS13A disease patients and 12 control subjects were analyzed by mass spectrometry (lipidomics).

RESULTS

While we found no significant differences in the overall lipid class level, alterations in certain species were detected: phosphatidylethanolamine species with both longer chain length and higher unsaturation were increased in VPS13A disease samples. Specific ceramide, phosphatidylcholine, and sphingomyelin species were also altered.

CONCLUSIONS

The presented alterations of particular lipid species in RBCs in VPS13A disease may contribute to (1) the understanding of acanthocyte formation, and (2) future biomarker identification. Lipid distribution seems to play a key role in the pathophysiology of VPS13A disease. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Clinical Features and Novel Pathogenic Variants of Chinese Patients With McLeod Syndrome and Chorea-Acanthocytosis

BACKGROUND

McLeod syndrome (MLS) and chorea-acanthocytosis (ChAc) are exceedingly rare diseases characterized by a variety of movement disorders including chorea, dystonia, and Parkinsonism. Genetic analysis plays a key role in early and accurate diagnosis, but relevant variants are still under investigation. This study aims to explore new pathogenic variants in Chinese patients with MLS and ChAc and to conduct a comprehensive analysis of the clinical heterogeneity among these patients.

METHODS

Eighteen Chinese patients who presented with choreatic movements with negative HTT genetic testing were identified and underwent targeted next-generation sequencing, verified by Sanger sequencing.

RESULTS

Two novel XK variants (c.970A>T, c.422_423del) were identified in three index MLS patients and six novel VPS13A variants (c.9219C>A, c.3467T>A, c.4208dup, c.9243_9246del, c.5364del, c.556-290_697-483del) in five index ChAc patients. One copy number variant of VPS13A (g.79827595_79828762del/c.556-290_697-483del) was firstly described in Chinese population.

CONCLUSION

As the currently largest descriptive study of MLS and ChAc patients in China, this study expands on the clinical and genetic spectrum of XK and VPS13A, contributing to the clinical diagnosis of MLS and ChAc.

Recent advances in non-Huntington's disease choreas

INTRODUCTION

Chorea is primarily due to an imbalance of basal ganglia output pathways, often due to dysfunction or degeneration of the caudate nucleus and putamen, and can be due to many causes.

METHODS

We reviewed the recent literature to identify newly-recognized causes of chorea, including auto-immune, metabolic, and genetic. We also focused upon developments in mechanisms relating to underlying pathophysiology of certain genetic choreas and advances in therapeutics.

RESULTS

Novel autoantibodies continue to be identified as causes of chorea. Both COVID-19 infection and vaccination are reported to result rarely in chorea, although in some cases causality is not clearly established. Advances in genetic testing continue to find more causes of chorea, and to expand the phenotype of known genetic disorders. Deep brain stimulation can be successful in certain circumstances.

CONCLUSION

Our understanding of mechanisms underlying this movement disorder continues to advance, however much remains to be elucidated.

Neuroacanthocytosis Syndromes: The Clinical Perspective

The two very rare neurodegenerative diseases historically known as the "neuroacanthocytosis syndromes" are due to mutations of either VPS13A or XK. These are phenotypically similar disorders that affect primarily the basal ganglia and hence result in involuntary abnormal movements as well as neuropsychiatric and cognitive alterations. There are other shared features such as abnormalities of red cell membranes which result in acanthocytes, whose relationship to neurodegeneration is not yet known. Recent insights into the functions of these two proteins suggest dysfunction of lipid processing and trafficking at the subcellular level and may provide a mechanism for neuronal dysfunction and death, and potentially a target for therapeutic interventions.