Dysfunction of spatacsin leads to axonal pathology in SPG11-linked hereditary spastic paraplegia.

Francesc Pérez-Brangulí,Iryna Prots,Jürgen Winkler,Martin Regensburger,Teja W Groemer,Ursula Schlötzer-Schrehardt,Juan Blasi,Steven Havlicek,Beate Winner,Jonatan Dorca-Arevalo,Himanshu K Mishra,Daniela Graef,Zacharias Kohl,Domenica Saul,Elisabeth Sock,Christine Rummel

doi:10.1093/hmg/ddu200

Francesc Pérez-Brangulí, Iryna Prots + Show 14 more

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https://doi.org/10.1093/hmg/ddu200

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Abstract

Hereditary spastic paraplegias are a group of inherited motor neuron diseases characterized by progressive paraparesis and spasticity. Mutations in the spastic paraplegia gene SPG11, encoding spatacsin, cause an autosomal-recessive disease trait; however, the precise knowledge about the role of spatacsin in neurons is very limited. We for the first time analyzed the expression and function of spatacsin in human forebrain neurons derived from human pluripotent stem cells including lines from two SPG11 patients and two controls. SPG11 patients'-derived neurons exhibited downregulation of specific axonal-related genes, decreased neurite complexity and accumulation of membranous bodies within axonal processes. Altogether, these data point towards axonal pathologies in human neurons with SPG11 mutations. To further corroborate spatacsin function, we investigated human pluripotent stem cell-derived neurons and mouse cortical neurons. In these cells, spatacsin was located in axons and dendrites. It colocalized with cytoskeletal and synaptic vesicle (SV) markers and was present in synaptosomes. Knockdown of spatacsin in mouse cortical neurons evidenced that the loss of function of spatacsin leads to axonal instability by downregulation of acetylated tubulin. Finally, time-lapse assays performed in SPG11 patients'-derived neurons and spatacsin-silenced mouse neurons highlighted a reduction in the anterograde vesicle trafficking indicative of impaired axonal transport. By employing SPG11 patient-derived forebrain neurons and mouse cortical neurons, this study provides the first evidence that SPG11 is implicated in axonal maintenance and cargo trafficking. Understanding the cellular functions of spatacsin will allow deciphering mechanisms of motor cortex dysfunction in autosomal-recessive hereditary spastic paraplegia.

Highlights

Hereditary spastic paraplegias (HSPs) are a heterogeneous group of neurodegenerative disorders commonly characterized by the degeneration of long axons of the cortico-spinal tract and dorsal columns [1]
By employing SPG11 patientderived forebrain neurons and mouse cortical neurons, this study provides the first evidence that SPG11 is implicated in axonal maintenance and cargo trafficking
We investigated the expression of spatacsin in human neurons derived either from human embryonic stem cells (HUES6-dNeurons, Fig. 1A) or from human-induced pluripotent stem cells and observed that spatacsin is expressed throughout neuronal differentiation

Summary

Introduction

Hereditary spastic paraplegias (HSPs) are a heterogeneous group of neurodegenerative disorders commonly characterized by the degeneration of long axons of the cortico-spinal tract and dorsal columns [1]. Genetic mapping and exome sequencing have identified at least 71 HSP gene loci, designated SPG 1-71, and up to date 54 genes causing an. Mutations in SPG11 are the most frequent cause of AR-HSP. Mutations in SPG11 were first described by screening patients with AR-HSP, thin corpus callosum (TCC) and cognitive impairment [3]. Additional symptoms including pseudobulbar symptoms such as dysarthria and dysphagia, neuropathy and amyotrophy are present in some patients with SPG11 mutations [4,5]

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