Cerebellar axonopathy in Shivers

Cerebellar axonopathy in Shivers horses identified by spatial transcriptomic and proteomic analyses
J Vet Intern Med. 2023 Jun 8. doi: 10.1111/jvim.16784. Online ahead of print.
Authors
Stephanie J Valberg 1 , Zoë J Willams 2 , Marisa L Henry 1 , Carrie J Finno 3
Affiliations

1 Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA.
2 C. Wayne McIlwraith Translational Medicine, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.
3 Department of Population Health and Reproduction, School of Veterinary Medicine, University of California-Davis, Davis, California, USA.

PMID: 37288990
DOI: 10.1111/jvim.16784

Abstract

Background: Shivers in horses is characterized by abnormal hindlimb movement when walking backward and is proposed to be caused by a Purkinje cell (PC) axonopathy based on histopathology.

Objectives: Define region-specific differences in gene expression within the lateral cerebellar hemisphere and compare cerebellar protein expression between Shivers horses and controls.

Animals: Case-control study of 5 Shivers and 4 control geldings ≥16.2 hands in height.

Methods: Using spatial transcriptomics, gene expression was compared between Shivers and control horses in PC soma and lateral cerebellar hemisphere white matter, consisting primarily of axons. Tandem-mass-tag (TMT-11) proteomic analysis was performed on lateral cerebellar hemisphere homogenates.

Results: Differences in gene expression between Shivers and control horses were evident in principal component analysis of axon-containing white matter but not PC soma. In white matter, there were 455/1846 differentially expressed genes (DEG; 350 ↓DEG, 105 ↑DEG) between Shivers and controls, with significant gene set enrichment of the Toll-Like Receptor 4 (TLR4) cascade, highlighting neuroinflammation. There were 50/936 differentially expressed proteins (DEP). The 27 ↓DEP highlighted loss of axonal proteins including intermediate filaments (5), myelin (3), cytoskeleton (2), neurite outgrowth (2), and Na/K ATPase (1). The 23 ↑DEP were involved in the extracellular matrix (7), cytoskeleton (7), redox balance (2), neurite outgrowth (1), signal transduction (1), and others.

Conclusion and clinical importance: Our findings support axonal degeneration as a characteristic feature of Shivers. Combined with histopathology, these findings are consistent with the known distinctive response of PC to injury where axonal changes occur without a substantial impact on PC soma.

Keywords: gene expression; movement disorder; neurology; protein expression; shivering.