The long non-coding RNA nuclear-enriched abundant transcript 1_2 induces paraspeckle formation in the motor neuron during the early phase of amyotrophic lateral sclerosis

Yoshinori Nishimoto,Shinichi Nakagawa,Norihiro Suzuki,Hirotaka Okano,Masaki Takao,Hideyuki Okano,Ken-Ichiro Kuwako,Takao Imai,Satoshi Suyama,Shigeo Murayama,Shinsuke Shibata,Tetsuro Hirose

doi:10.1186/1756-6606-6-31

Abstract

BackgroundA long non-coding RNA (lncRNA), nuclear-enriched abundant transcript 1_2 (NEAT1_2), constitutes nuclear bodies known as “paraspeckles”. Mutations of RNA binding proteins, including TAR DNA-binding protein-43 (TDP-43) and fused in sarcoma/translocated in liposarcoma (FUS/TLS), have been described in amyotrophic lateral sclerosis (ALS). ALS is a devastating motor neuron disease, which progresses rapidly to a total loss of upper and lower motor neurons, with consciousness sustained. The aim of this study was to clarify the interaction of paraspeckles with ALS-associated RNA-binding proteins, and to identify increased occurrence of paraspeckles in the nucleus of ALS spinal motor neurons.ResultsIn situ hybridization (ISH) and ultraviolet cross-linking and immunoprecipitation were carried out to investigate interactions of NEAT1_2 lncRNA with ALS-associated RNA-binding proteins, and to test if paraspeckles form in ALS spinal motor neurons. As the results, TDP-43 and FUS/TLS were enriched in paraspeckles and bound to NEAT1_2 lncRNA directly. The paraspeckles were localized apart from the Cajal bodies, which were also known to be related to RNA metabolism. Analyses of 633 human spinal motor neurons in six ALS cases showed NEAT1_2 lncRNA was upregulated during the early stage of ALS pathogenesis. In addition, localization of NEAT1_2 lncRNA was identified in detail by electron microscopic analysis combined with ISH for NEAT1_2 lncRNA. The observation indicating specific assembly of NEAT1_2 lncRNA around the interchromatin granule-associated zone in the nucleus of ALS spinal motor neurons verified characteristic paraspeckle formation.ConclusionsNEAT1_2 lncRNA may act as a scaffold of RNAs and RNA binding proteins in the nuclei of ALS motor neurons, thereby modulating the functions of ALS-associated RNA-binding proteins during the early phase of ALS. These findings provide the first evidence of a direct association between paraspeckle formation and a neurodegenerative disease, and may shed light on the development of novel therapeutic targets for the treatment of ALS.

Highlights

A long non-coding RNA, nuclear-enriched abundant transcript 1_2 (NEAT1_2), constitutes nuclear bodies known as “paraspeckles”
Among the genes associated with familial amyotrophic lateral sclerosis (ALS), mutations in TAR DNA-binding protein-43 (TDP43), fused in sarcoma/translocated in liposarcoma (FUS/ TLS), optineurin and SQSTM1, and hexanucleotide repeat expansion in C9ORF72 were identified in sporadic ALS cases [2,3,4,5,6,7]
TAR DNA-binding protein-43 (TDP-43) and fused in sarcoma/translocated in liposarcoma (FUS/TLS) are enriched in nuclear paraspeckles in cultured cells Characteristics of NEAT1_2 long non-coding RNA (lncRNA) and paraspeckle formation have been elucidated mainly using cultured cells including HeLa cells [16,17,18,19,20,28,29,30,31,32,33,34]

Summary

Introduction

A long non-coding RNA (lncRNA), nuclear-enriched abundant transcript 1_2 (NEAT1_2), constitutes nuclear bodies known as “paraspeckles”. Mutations of RNA binding proteins, including TAR DNA-binding protein-43 (TDP-43) and fused in sarcoma/translocated in liposarcoma (FUS/TLS), have been described in amyotrophic lateral sclerosis (ALS). The aim of this study was to clarify the interaction of paraspeckles with ALS-associated RNA-binding proteins, and to identify increased occurrence of paraspeckles in the nucleus of ALS spinal motor neurons. Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder characterized by loss of upper and lower motor neurons. Among the genes associated with familial ALS, mutations in TAR DNA-binding protein-43 (TDP43), fused in sarcoma/translocated in liposarcoma (FUS/ TLS), optineurin and SQSTM1, and hexanucleotide repeat expansion in C9ORF72 were identified in sporadic ALS cases [2,3,4,5,6,7]. TDP-43 and FUS/TLS play critical roles in RNA processing [13]; the association of these RNAbinding proteins with ALS pathogenesis remains mostly unknown

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