Fused in Sarcoma (FUS) Protein Lacking Nuclear Localization Signal (NLS) and Major RNA Binding Motifs Triggers Proteinopathy and Severe Motor Phenotype in Transgenic Mice

Sandrine Da Cruz,Owen M Peters,Igor L Goldman,Tatyana G Ermolkevich,Elena R Sadchikova,Elena A Kovrazhkina,Hannah Robinson,Sergey O Bachurin,Tatyana A Shelkovnikova,Alexey V Deykin,Vladimir L Buchman,Philippe A Parone,Natalie Connor-Robson,Shuo-Chien Ling,Veronica I Skvortsova,Alexey A Ustyugov,Natalia N Ninkina

doi:10.1074/jbc.m113.492017

Abstract

Dysfunction of two structurally and functionally related proteins, FUS and TAR DNA-binding protein of 43 kDa (TDP-43), implicated in crucial steps of cellular RNA metabolism can cause amyotrophic lateral sclerosis (ALS) and certain other neurodegenerative diseases. The proteins are intrinsically aggregate-prone and form non-amyloid inclusions in the affected nervous tissues, but the role of these proteinaceous aggregates in disease onset and progression is still uncertain. To address this question, we designed a variant of FUS, FUS 1-359, which is predominantly cytoplasmic, highly aggregate-prone, and lacks a region responsible for RNA recognition and binding. Expression of FUS 1-359 in neurons of transgenic mice, at a level lower than that of endogenous FUS, triggers FUSopathy associated with severe damage of motor neurons and their axons, neuroinflammatory reaction, and eventual loss of selective motor neuron populations. These pathological changes cause abrupt development of a severe motor phenotype at the age of 2.5-4.5 months and death of affected animals within several days of onset. The pattern of pathology in transgenic FUS 1-359 mice recapitulates several key features of human ALS with the dynamics of the disease progression compressed in line with shorter mouse lifespan. Our data indicate that neuronal FUS aggregation is sufficient to cause ALS-like phenotype in transgenic mice.

Highlights

FUS inclusions are hallmarks of certain neurodegenerative diseases
In the central nervous system of hemizygous FUS 1–359 TG 19 mice, the 55-kDa truncated human protein was expressed at a lower level than the 70-kDa endogenous mouse FUS protein (Fig. 1E), and these animals developed a severe neurological phenotype early in their life
Animals of FUS 1–359 TG line 6 expressed substantially less human protein in their nervous system when compared with line 19 (Fig. 1F), and only in aging homozygous line 6 mice were FUS-positive aggregates observed in a small proportion of lower motor neurons

Summary

Background

FUS inclusions are hallmarks of certain neurodegenerative diseases. Results: Expression of a highly aggregate prone FUS variant in transgenic mice causes proteinopathy and severe motor phenotype. The question of whether FUS aggregation is sufficient to cause pathological changes typical for FUSopathies or whether its altered function in RNA metabolism plays a primary role in the pathology development is still to be answered Findings supporting the latter mechanism were reported [8], but the importance of FUS aggregation with formation of FUS positive inclusions in the affected neurons as triggers of pathological changes has never been directly addressed. We demonstrate that expression of a relatively low level of FUS 1–359 protein in neurons of transgenic mice triggers FUSopathy and severe motor neuron pathology, recapitulating certain key features of human diseases associated with FUS aggregation and dysfunction

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION