Combined Dendritic and Axonal Deterioration Are Responsible for Motoneuronopathy in Patient-Derived Neuronal Cell Models of Chorea-Acanthocytosis

Abstract

Chorea acanthocytosis (ChAc), an ultra-rare devastating neurodegenerative disease, is caused by mutations in the VPS13A gene, which encodes for the protein chorein. Affected patients suffer from chorea, orofacial dyskinesia, epilepsy, parkinsonism as well as peripheral neuropathy. Although medium spinal neurons of the striatum are mainly affected, other regions are impaired as well over the course of the disease. Animal studies as well as studies on human erythrocytes suggest Lyn-kinase inhibition as valuable novel opportunity to treat ChAc. In order to investigate the peripheral neuropathy aspect, we analyzed induced pluripotent stem cell derived midbrain/hindbrain cell cultures from ChAc patients in vitro. We observed dendritic microtubule fragmentation. Furthermore, by using in vitro live cell imaging, we found a reduction in the number of lysosomes and mitochondria, shortened mitochondria, an increase in retrograde transport and hyperpolarization as measured with the fluorescent probe JC-1. Deep phenotyping pointed towards a proximal axonal deterioration as the primary axonal disease phenotype. Interestingly, pharmacological interventions, which proved to be successful in different models of ChAc, were ineffective in treating the observed axonal phenotypes. Our data suggests that treatment of this multifaceted disease might be cell type and/or neuronal subtype specific, and thus necessitates precision medicine in this ultra-rare disease.

Concomitant gain and loss of function pathomechanisms in C9ORF72 amyotrophic lateral sclerosis

“…All iPSC lines were matured to spinal MNs in microfluidic chambers (MFCs), in which only axons could reach and fully penetrate the microgroove barrier of channels from the proximal soma seeding site to distal exits ( Naumann et al, 2018 ) ( Fig 1A ), thereby enabling axon-specific studies with defined antero- versus retrograde orientation. Of note, our differentiation protocol combined with 900 μm length of microgrooves resulted in exclusive penetration by MN axons, as we documented previously ( Pal et al, 2018 ; Glaβ et al, 2020 ). We performed fast dual-color live imaging of mitochondria and lysosomes at strictly standardized distal versus proximal readout positions as described ( Naumann et al, 2018 ) on day D21.…”

“…The cultures were devoid of glia cells and astrocytes. Neurites penetrating the microchannels and sprouting out at the distal exit are virtually 100% axon-pure ( Glaβ et al, 2020 ).…”

Unraveling the Spatiotemporal Distribution of VPS13A in the Mouse Brain

“…The main neuropathologic feature in VPS13A disease is a selective degeneration of the caudate and putamen nuclei [ 4 , 5 , 6 ], due to massive cell death of medium spiny neurons (MSNs) and striatal interneurons [ 7 , 8 ]. Moreover, many other neuronal subtypes, such as dopaminergic neurons or motoneurons, are affected as well, contributing to the explanation of a plethora of pathological symptoms that include chorea, dystonia, involuntary oral biting, and orofacial dyskinesia, among others [ 9 ].…”

Alteration of Mitochondrial Integrity as Upstream Event in the Pathophysiology of SOD1-ALS

“…The coating and assembly of MFCs (Xona Microfluidics RD900) to prepare for the seeding of MNs was performed as described [ 25 , 36 , 38 ]. MNs were seeded for maturation into one side of an MFC to obtain a fully compartmentalized culture with proximal somas and their dendrites being physically separated from their distal axons, as only the latter type of neurite was capable to grow from the proximal seeding site through a microgroove barrier of 900 µm-long microchannels to the distal site (shown in details in [ 43 ]). All subsequent imaging in MFCs was performed at day (D)21 of axonal growth and MN maturation (D0 = day of seeding into MFCs).…”