Cytoplasmic mislocalization of RNA splicing factors and aberrant neuronal gene splicing in TDP-43 transgenic pig brain.

Guohao Wang,Xudong Liu,Liangxue Lai,Zhaoming Liu,Zhen Ouyang,Sen Yan,Nana Fan,Tao Liu,Xiao-Jiang Li,Huaqiang Yang,Lin Guo,Chuan-En Wang,Peng Yin,Shihua Li,Yu Zhao,Bentian Zhao

doi:10.1186/s13024-015-0036-5

Abstract

BackgroundTAR DNA-binding protein 43 (TDP-43) is a nuclear protein, but it is redistributed in the neuronal cytoplasm in both amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). Because small transgenic animal models often lack cytoplasmic TDP-43, how the cytoplasmic accumulation of TDP-43 contributes to these diseases remains unclear. The current study is aimed at studying the mechanism of cytoplasmic pathology of TDP-43.ResultsWe established transgenic pigs expressing mutant TDP-43 (M337V). This pig model shows severe phenotypes and early death. We found that transgenic TDP-43 is also distributed in the cytoplasm of neuronal cells in the spinal cord and brain. Transgenic TDP-43 interacts with PSF, an RNA splicing factor that associates with NeuN to regulate neuronal RNA splicing. The interaction of TDP-43, PSF and NeuN causes PSF and NeuN mislocalize into the neuronal cytoplasm in transgenic pigs. Consistently, abnormal PSF-related neuronal RNA splicing is seen in TDP-43 transgenic pigs. The cytoplasmic localization of PSF and NeuN as well as abnormal PSF-related neuronal RNA splicing was also found in ALS patient brains.ConclusionOur findings from a large mammalian model suggest that cytoplasmic mutant TDP-43 could reduce the nuclear function of RNA splicing factors, contributing to neuropathology.

Highlights

TAR DNA-binding protein 43 (TDP-43) is a nuclear protein, but it is redistributed in the neuronal cytoplasm in both amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD)
Generation of transgenic pigs expressing mutant TDP-43 There are a number of mutations in human TDP-43, and transgenic expression of wild type human TDP-43 causes neuropathology in animal models [22, 28]
Considering that generation of transgenic pigs is much more time-consuming and costly than small animal models, we focused on the generation of transgenic pigs expressing human mutant TDP-43 (M337V), but not wild type TDP-43, and compared them with nontransgenic pigs

Summary

Introduction

TAR DNA-binding protein 43 (TDP-43) is a nuclear protein, but it is redistributed in the neuronal cytoplasm in both amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). Because small transgenic animal models often lack cytoplasmic TDP-43, how the cytoplasmic accumulation of TDP-43 contributes to these diseases remains unclear. A variety of transgenic TDP-43 animal models have been established and provided us with valuable tools to uncover gene expression alteration and aberrant RNA splicing caused by TDP-43 [5, 7, 15]. TDP-43, many transgenic TDP-43 mouse models fail to show the cytoplasmic accumulation of mutant TDP-43 [16,17,18,19,20,21,22,23,24], suggesting that species-dependent differences may account for differential pathology of TDP-43 in small animals and human patients. Because most of current animal models lack the cytoplasmic accumulation of TDP-43, our ability to investigate how the cytoplasmic mislocalization of TDP-43 contributes to the pathogenesis has been limited

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Discussion

Conclusion