Mutant TDP-43 in Astrocytes Kills Motor Neurons in Rats through Neurotoxic Gain and Neuroprotective Loss in Astrocytes

Mutation in TDP-43 is causative to amyotrophic lateral sclerosis (ALS). TDP-43 is a multifunctional ribonucleoprotein and is reproted to regulate thousands of genes in neurons, but how astrocytes contribute to TDP-43 pathogenesis is not known. This study examined how mutant TDP-43 in astrocytes kills motor neurons and causes ALS phenotypes. Primary astrocytes were isolated from transgenic rats expressing mutant TDP-43 or from control rats without mutant TDP-43 expression. Cultured astrocytes were induced to express mutant human TDP-43 and their gene expression profiles were determined by microarray assays. Microarray analysis revealed that hundreds of genes were altered in astrocytes in response to mutant TDP-43 expression. As mutant TDP-43 transgene is under the control of tetracycline-regulated pomoter elements (TRE), mutant TDP-43 expression is subjected to Doxycline regulation. Astrocytes isolated from GFAP-tTA/TRE-TDP43M337V rats were desiginated as M337V groups and astrocytes isolated from GFAP-tTA single transgenic rats were desiginated as tTA control groups. Total RNA was isolated from cultured astrocytes at varying times (3, 4, or 6 days after Dox withdrawal) after mutant TDP-43 was induced in astrocytes. Upon mutant TDP-43 induction in astroyctes, gene expression profiles in astroyctes were determined by Illumina Direct Hybridization Assay and compared between tTA and M337V groups at the varying time points of mutant TDP-43 induction.