Alexander Disease Modeling in Zebrafish: An In Vivo System Suitable to Perform Drug Screening.

Simona Candiani,Daniele Bani,Andreas F Mack,Mario Pestarino,Tiziana Bachetti,Matteo Bozzo,Valentina Obino,Francesca Rosamilia,Silvia Carestiato,Michela Ori,Miriam De Sarlo,Isabella Ceccherini

doi:10.3390/genes11121490

Abstract

Alexander disease (AxD) is a rare astrogliopathy caused by heterozygous mutations, either inherited or arising de novo, on the glial fibrillary acid protein (GFAP) gene (17q21). Mutations in the GFAP gene make the protein prone to forming aggregates which, together with heat-shock protein 27 (HSP27), αB-crystallin, ubiquitin, and proteasome, contribute to form Rosenthal fibers causing a toxic effect on the cell. Unfortunately, no pharmacological treatment is available yet, except for symptom reduction therapies, and patients undergo a progressive worsening of the disease. The aim of this study was the production of a zebrafish model for AxD, to have a system suitable for drug screening more complex than cell cultures. To this aim, embryos expressing the human GFAP gene carrying the most severe p.R239C under the control of the zebrafish gfap gene promoter underwent functional validation to assess several features already observed in in vitro and other in vivo models of AxD, such as the localization of mutant GFAP inclusions, the ultrastructural analysis of cells expressing mutant GFAP, the effects of treatments with ceftriaxone, and the heat shock response. Our results confirm that zebrafish is a suitable model both to study the molecular pathogenesis of GFAP mutations and to perform pharmacological screenings, likely useful for the search of therapies for AxD.

Highlights

Alexander disease (AxD) is a rare autosomal dominant astrogliopathy, characterized by progressively increasing severity and fatal outcome
One of the most severe glial fibrillary acid protein (GFAP) mutations recognized as causative of AxD is the missense p.R239C, which we used to create a zebrafish model of the disease
We investigated whether small heat-shock proteins (sHSPs) induction, produced by heat-shock stimulation, could have beneficial effects on mutant GFAP aggregates in zebrafish embryos

Summary

Introduction

Alexander disease (AxD) is a rare autosomal dominant astrogliopathy, characterized by progressively increasing severity and fatal outcome. AxD comprises two different clinical forms according to age at onset and decreasing progressive severity, namely, Type I AxD Genes 2020, 11, 1490 of age) and Type II AxD (late onset, >4 years of age) [1]. The vast majority of AxD patients are characterized by heterozygous mutations in the GFAP gene [3], formed of nine exons on chromosome 17q21 [4]. In addition to GFAP mutations, wildtype GFAP overexpression induces the formation of intracellular protein aggregates, suggesting that the gene expression level is a modifier element of the disease expressivity [6] and that regulation of GFAP expression may be a pharmacological target in AxD

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