Teaching NeuroImage: Unilateral Primary Angiitis of the CNS

A 48-year-old woman was referred with an 18-year history of focal-onset seizures. She also reported years-long slowly progressive right-sided weakness that was corroborated on examination. Repeated brain MRIs over 15 years showed multifocal left hemispheric T2 fluid-attenuated inversion recovery-hyperintense lesions with patchy enhancement and microhemorrhages, no diffusion restriction, and a left cerebellar infarct (Figure 1, A-F). Only 2 nonspecific white matter lesions were seen contralaterally, indicating largely unihemispheric disease. Differential diagnosis included unilateral primary angiitis of the CNS (PACNS), Rasmussen encephalitis, and myelin oligodendrocyte glycoprotein antibody-associated disease.1 Serum and CSF testing for autoimmune, infectious, and malignant etiologies and whole-body fluorodeoxyglucose-PET, whole-exome genetic sequencing, and MR vessel-wall imaging were nondiagnostic. Brain biopsy revealed vasculitis (Figure 2, A-F), and the patient was diagnosed with unilateral PACNS. Treatment with mycophenolate mofetil has been initiated. Unilateral PACNS is a rare unihemispheric disease characterized by an indolent course and seizures, recognition of which is critical to accurate diagnosis.1,2.

Sticking to your side: A niche for the development of ipsilateral retinal projections

Visual impairments in albinism result from decreased ipsilateral retinal projections. In this issue of Neuron, Slavi, Balasubramanian, and colleagues¹ demonstrate how low CyclinD2 in the ciliary marginal zone perturbs generation of ipsilaterally projecting RGCs and that restoring CyclinD2 improves vision in albino mice.

Human serum antibodies against EBV latent membrane protein 1 cross-react with α-synuclein

Objectives:

To identify the epitope on α-synuclein (α-syn) to which antibodies against the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) bind and to determine whether antibodies targeting this mimicry domain are present in human sera.

Methods:

Reactivity of the α-syn-cross-reacting anti-LMP1 monoclonal antibody CS1-4 to a synthetic peptide containing the putative mimicry domain was compared to those in which this domain was mutated and to murine and rat α-syn (which differ from human α-syn at this site) in Western blots. Using ELISA, sera from EBV+ (n = 4) and EBV− (n = 12) donors as well as those with infectious mononucleosis (IM; n = 120), and Hodgkin disease (HD; n = 33) were interrogated for antibody reactivity to synthetic peptides corresponding to regions of α-syn and LMP1 containing the mimicry domain.

Results:

CS1-4 showed strong reactivity to wild-type human α-syn, but not to the mutant peptides or rodent α-syn. Control EBV− and EBV+ sera showed no reactivity to α-syn or LMP1 peptides. However, a significant proportion of IM and HD sera contained immunoglobulin M (IgM) (59% and 70%, in IM and HD, respectively), immunoglobulin G (IgG) (40% and 48%), and immunoglobulin A (IgA) (28% and 36%) antibodies to both peptides, as well as a significant correlation in the titers of IgM (ρ = 0.606 and 0.664, for IM and HD, respectively), IgG (0.526 and 0.836), and IgA (0.569 and 0.728) antibodies targeting LMP1 and α-syn peptides.

Conclusions:

Anti-EBV-LMP1 antibodies cross-reacting with a defined epitope in α-syn are present in human patients. These findings may have implications for the pathogenesis of synucleinopathies.

Electric Field Control of Interfacial Ferromagnetism in CaMnO_{3}/CaRuO_{3} Heterostructures

New mechanisms for achieving direct electric field control of ferromagnetism are highly desirable in the development of functional magnetic interfaces. To that end, we have probed the electric field dependence of the emergent ferromagnetic layer at CaRuO_{3}/CaMnO_{3} interfaces in bilayers fabricated on SrTiO_{3}. Using polarized neutron reflectometry, we are able to detect the ferromagnetic signal arising from a single atomic monolayer of CaMnO_{3}, manifested as a spin asymmetry in the reflectivity. We find that the application of an electric field of 600 kV/m across the bilayer induces a significant increase in this spin asymmetry. Modeling of the reflectivity suggests that this increase corresponds to a transition from canted antiferromagnetism to full ferromagnetic alignment of the Mn^{4+} ions at the interface. This increase from 1 μ_{B} to 2.5-3.0 μ_{B} per Mn is indicative of a strong magnetoelectric coupling effect, and such direct electric field control of the magnetization at an interface has significant potential for spintronic applications.

Striatal blood-brain barrier permeability in Parkinson's disease

In vivo studies have shown that blood-brain barrier (BBB) dysfunction is involved in the course of Parkinson's disease (PD). However, these have lacked either anatomic definition or the ability to recognize minute changes in BBB integrity. Here, using histologic markers of serum protein, iron, and erythrocyte extravasation, we have shown significantly increased permeability of the BBB in the postcommissural putamen of PD patients. The dense innervation of the striatum by PD-affected regions allows for exploitation of this permeability for therapeutic goals. These results are also discussed in the context of the retrograde trans-synaptic hypothesis of PD spread.

Loss of UCHL1 promotes age-related degenerative changes in the enteric nervous system

UCHL1 (ubiquitin carboxyterminal hydrolase 1) is a deubiquitinating enzyme that is particularly abundant in neurons. From studies of a spontaneous mutation arising in a mouse line it is clear that loss of function of UCHL1 generates profound degenerative changes in the central nervous system, and it is likely that a proteolytic deficit contributes to the pathology. Here these effects were found to be recapitulated in mice in which the Uchl1 gene had been inactivated by homologous recombination. In addition to the previously documented neuropathology associated with loss of UCHL1 function, axonal swellings were detected in the striatum. In agreement with previously reported findings the loss of UCHL1 function was accompanied by perturbations in ubiquitin pools, but glutathione levels were also significantly depleted in the brains of the knockout mice, suggesting that oxidative defense mechanisms may be doubly compromised. To determine if, in addition to its role in the central nervous system, UCHL1 function is also required for homeostasis of the enteric nervous system the gastrointestinal tract was analyzed in UCHL1 knockout mice. The mice displayed functional changes and morphological changes in gut neurons that preceded degenerative changes in the brain. The changes were qualitatively and quantitatively similar to those observed in wild type mice of much greater age, and strongly resemble changes reported for elderly humans. UCHL1 knockout mice should therefore serve as a useful model of gut aging.

Alpha-synuclein in the appendiceal mucosa of neurologically intact subjects

Parkinson's disease is characterized by the pathological aggregation of Alpha-synuclein. The dual-hit hypothesis proposed by Braak implicates the enteric nervous system as an initial site of α-synuclein aggregation with subsequent spread to the central nervous system. Regional variations in the spatial pattern or levels of α-synuclein along the enteric nervous system could have implications for identifying sites of onset of this pathogenic cascade. We performed immunohistochemical staining for α-synuclein on gastrointestinal tissue from patients with no history of neurological disease using the established LB509 antibody and a new clone, MJFR1, characterized for immunohistochemistry here. We demonstrate that the vermiform appendix is particularly enriched in α-synuclein-containing axonal varicosities, concentrated in its mucosal plexus rather than the classical submucosal and myenteric plexuses. Unexpectedly, intralysosomal accumulations of α-synuclein were detected within mucosal macrophages of the appendix. The abundance and accumulation of α-synuclein in the vermiform appendix implicate it as a candidate anatomical locus for the initiation of enteric α-synuclein aggregation and permits the generation of testable hypotheses for Parkinson's disease pathogenesis.