Dystrophin Distribution and Expression in Human and Experimental Temporal Lobe Epilepsy.

Ruben G F Hendriksen,Johan S H Vles,Sandra Schipper,Govert Hoogland,Olaf E M G Schijns,Jim T A Dings,Marlien W Aalbers

doi:10.3389/fncel.2016.00174

Abstract

Objective: Dystrophin is part of a protein complex that connects the cytoskeleton to the extracellular matrix. In addition to its role in muscle tissue, it functions as an anchoring protein within the central nervous system such as in hippocampus and cerebellum. Its presence in the latter regions is illustrated by the cognitive problems seen in Duchenne Muscular Dystrophy (DMD). Since epilepsy is also supposed to constitute a comorbidity of DMD, it is hypothesized that dystrophin plays a role in neuronal excitability. Here, we aimed to study brain dystrophin distribution and expression in both, human and experimental temporal lobe epilepsy (TLE).Method: Regional and cellular dystrophin distribution was evaluated in both human and rat hippocampi and in rat cerebellar tissue by immunofluorescent colocalization with neuronal (NeuN and calbindin) and glial (GFAP) markers. In addition, hippocampal dystrophin levels were estimated by Western blot analysis in biopsies from TLE patients, post-mortem controls, amygdala kindled (AK)-, and control rats.Results: Dystrophin was expressed in all hippocampal pyramidal subfields and in the molecular-, Purkinje-, and granular cell layer of the cerebellum. In these regions it colocalized with GFAP, suggesting expression in astrocytes such as Bergmann glia (BG) and velate protoplasmic astrocytes. In rat hippocampus and cerebellum there were neither differences in dystrophin positive cell types, nor in the regional dystrophin distribution between AK and control animals. Quantitatively, hippocampal full-length dystrophin (Dp427) levels were about 60% higher in human TLE patients than in post-mortem controls (p < 0.05), whereas the level of the shorter Dp71 isoform did not differ. In contrast, AK animals showed similar dystrophin levels as controls.Conclusion: Dystrophin is ubiquitously expressed by astrocytes in the human and rat hippocampus and in the rat cerebellum. Hippocampal full-length dystrophin (Dp427) levels are upregulated in human TLE, but not in AK rats, possibly indicating a compensatory mechanism in the chronic epileptic human brain.

Highlights

Dystrophin is an essential component of a protein complex that connects the cytoskeleton to the extracellular matrix
Rat Brain Dystrophin Distribution Dystrophin distribution was studied in rat hippocampus and rat cerebellum
The regional and cellular distribution of dystrophin did not differ between sham control and AK rats

Summary

Introduction

Dystrophin is an essential component of a protein complex that connects the cytoskeleton to the extracellular matrix. There is an increasing body of evidence stating that DMD is associated with non-progressive cognitive and behavioral deficits (Cotton et al, 2001; Hendriksen and Vles, 2006, 2008; Pane et al, 2012; Snow et al, 2013a) and epilepsy (Goodwin et al, 1997; Etemadifar and Molaei, 2004; Pane et al, 2013) This association is thought to result from the lack of dystrophin within the CNS, where it is normally located in the hippocampus, prefrontal cortex, and cerebellum (Chamberlain et al, 1989; Lidov et al, 1993). Different CNS cells express different Dp isoforms: full-length dystrophin (Dp427) is localized post-synaptically in neurons, Dp140 is associated with microvascular glia cells, and Dp71 − the most abundant dystrophin gene product in the brain – is both expressed in neurons and glia (Lidov et al, 1995; Blake and Kröger, 2002; Graciotti et al, 2008)

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