Pathogenesis of severe ataxia and tremor without the typical signs of neurodegeneration

Abstract

Neurological diseases are especially devastating when they involve neurodegeneration. Neuronal destruction is widespread in cognitive disorders such as Alzheimer’s and regionally localized in motor disorders such as Parkinson’s, Huntington’s, and ataxia. But, surprisingly, the onset and progression of these diseases can occur without neurodegeneration. To understand the origins of diseases that do not have an obvious neuropathology, we tested how loss of CAR8, a regulator of IP3R1-mediated Ca2+-signaling, influences cerebellar circuit formation and neural function as movement deteriorates. We found that faulty molecular patterning, which shapes functional circuits called zones, leads to alterations in cerebellar wiring and Purkinje cell activity, but not to degeneration. Rescuing Purkinje cell function improved movement and reducing their Ca2+ influx eliminated ectopic zones. Our findings in Car8wdl mutant mice unveil a pathophysiological mechanism that may operate broadly to impact motor and non-motor conditions that do not involve degeneration.

Genetic silencing of olivocerebellar synapses causes dystonia-like behaviour in mice

“…To test whether there are similar defects in the Ptf1a Cre ;Vglut2 fx/fx mice, we measured molecular layer thickness as a proxy for dendrite span. Molecular layer thickness is a sensitive and straightforward measure for developmental and disease-associated defects that disrupt Purkinje cell dendrite size and/or the placement of Purkinje cells into a perfect monolayer28. At birth and during postnatal development, molecular layer thickness was significantly less in Ptf1a Cre ;Vglut2 fx/fx compared with Vglut2 fx/fx mice (Fig.…”

“…Immunohistochemistry and in situ hybridization were carried out as described previously28. For in situ hybridization, mice were anaesthetized with isoflurane, brains rapidly removed from the skull and immersed in OCT (optimal cutting temperature), and immediately flash frozen by placing the tissue moulds into liquid nitrogen.…”

“…Mice were tested on the rotarod each day for 3 days with 3 trials separated by 15 min. Tremor amplitude and frequency were analysed on a single trial with a Tremor Monitor28 (San Diego Instruments, San Diego, CA, USA). Using the provided software from SDI, the raw waveforms were passed through a fast Fourier transform to create a power spectrum graph.…”

WGA‐Alexa Conjugates for Axonal Tracing

“…Here, zebrinII was used at 1:250 (kind gift from Dr. Richard Hawkes; R. Hawkes, University of Calgary; Alberta; Canada Cat# ZebrinII Lot# RRID:AB_2315622; Figure 4). Please see our previous publications for additional details on our specific procedures for immunohistochemistry (Sillitoe and Hawkes, 2002; Sillitoe et al, 2010; White et al, 2014; White et al, 2016a; White et al, 2016b). …”

“…For quantitative analysis we collect continuous traces of >300 seconds and examine spikes with Spike2 (Spike2 Software, RRID:SCR_000903), MS Excel, and MATLAB (Mathworks, Natick, MA). Please refer to our recent work for additional details on electrophysiology and the methods for analysis of spike properties (Arancillo et al, 2015; White et al, 2014; White et al, 2016b).

WGA-Alexa 488 (or WGA-Alexa 555) is diluted to 1% in a 100 ul 0.9% saline solution.

We fill low-impedance (1-3 MΩ), pulled borosilicate glass electrodes (GC150F-10, 1.5 OD X 0.86 ID X 100 L mm, Harvard Apparatus, Cambridge MA) with the WGA-Alexa solution.

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