Wild-Type and Mutant FUS Expression Reduce Proliferation and Neuronal Differentiation Properties of Neural Stem Progenitor Cells.

Eleonora Stronati,Giancarlo Poiana,Stefano Biagioni,Mauro Giorgi,Camilla Toselli,Emanuele Cacci,Mario Fiore

doi:10.3390/ijms22147566

Abstract

Nervous system development involves proliferation and cell specification of progenitor cells into neurons and glial cells. Unveiling how this complex process is orchestrated under physiological conditions and deciphering the molecular and cellular changes leading to neurological diseases is mandatory. To date, great efforts have been aimed at identifying gene mutations associated with many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Mutations in the RNA/DNA binding protein Fused in Sarcoma/Translocated in Liposarcoma (FUS/TLS) have been associated with motor neuron degeneration in rodents and humans. Furthermore, increased levels of the wild-type protein can promote neuronal cell death. Despite the well-established causal link between FUS mutations and ALS, its role in neural cells remains elusive. In order to shed new light on FUS functions we studied its role in the control of neural stem progenitor cell (NSPC) properties. Here, we report that human wild-type Fused in Sarcoma (WT FUS), exogenously expressed in mouse embryonic spinal cord-derived NSPCs, was localized in the nucleus, caused cell cycle arrest in G1 phase by affecting cell cycle regulator expression, and strongly reduced neuronal differentiation. Furthermore, the expression of the human mutant form of FUS (P525L-FUS), associated with early-onset ALS, drives the cells preferentially towards a glial lineage, strongly reducing the number of developing neurons. These results provide insight into the involvement of FUS in NSPC proliferation and differentiation into neurons and glia.

Highlights

Fused in Sarcoma/Translocated in Liposarcoma (FUS/TLS) belongs to the FET (FUSEWSR1, TAF15) family protein and was described for the first time in myxoid liposarcoma as an oncogenic fusion of the dominant negative transcription factor gene CHOP with the gene FUS [1,2]
FUS is implicated in the control of several stages of gene expression [9]: FUS controls transcription, as demonstrated by chromatin immunoprecitation combined with transcriptomic approaches that allowed to identify several FUS target genes [10]; microRNAs’ biogenesis, that is reduced by FUS/TLS depletion through a mechanism involving the modulation of the activity of Drosha [11]; and pre-mRNA processing as demonstrated by genome-wide analysis showing that thousands of RNA targets are bound by FUS [12,13,14], and by the fact that FUS deletion affects levels and splicing in about one thousand mRNAs [14]
Spinal cord-derived neural stem progenitor cell (NSPC) cell lines had been previously isolated in our laboratory and demonstrated to retain neural stem cell properties in vitro even after prolonged expansion [20,33,34]

Summary

Introduction

Fused in Sarcoma/Translocated in Liposarcoma (FUS/TLS) belongs to the FET (FUSEWSR1, TAF15) family protein and was described for the first time in myxoid liposarcoma as an oncogenic fusion of the dominant negative transcription factor gene CHOP with the gene FUS [1,2]. The interest in this protein has dramatically increased since a causative link was demonstrated between heritable and de novo FUS mutations and the dominant form of amyotrophic lateral sclerosis (ALS) [3,4,5]. Many studies pointed out that both the loss of nuclear function and the cytoplasmic gain of function of FUS lead to ALS-associated neurodegeneration in patients and in animal models [15,16]

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