NOS1AP is a novel molecular target and critical factor in TDP-43 pathology

Many lines of evidence have highlighted the role played by heterogeneous nuclear ribonucleoproteins in amyotrophic lateral sclerosis. In this study, we have aimed to identify transcripts co-regulated by TAR DNA-binding protein 43 kDa and highly conserved heterogeneous nuclear ribonucleoproteins which have been previously shown to regulate TAR DNA-binding protein 43 kDa toxicity (deleted in azoospermia-associated protein 1, heterogeneous nuclear ribonucleoprotein -Q, -D, -K and -U). Using the transcriptome analyses, we have uncovered that <i>Nitric Oxide Synthase 1 Adaptor Protein</i> mRNA is a direct TAR DNA-binding protein 43 kDa target, and in flies, its modulation alone can rescue TAR DNA-binding protein 43 kDa pathology. In primary mouse cortical neurons, we show that TAR DNA-binding protein 43 kDa mediated downregulation of <i>Nitric Oxide Synthase 1 Adaptor Protein</i> expression strongly affects the NMDA-receptor signalling pathway. In human patients, the downregulation of <i>Nitric Oxide Synthase 1 Adaptor Protein</i> mRNA strongly correlates with TAR DNA-binding protein 43 kDa proteinopathy as measured by cryptic <i>Stathmin-2</i> and Unc-13 homolog A cryptic exon inclusion. Overall, our results demonstrate that <i>Nitric Oxide Synthase 1 Adaptor Protein</i> may represent a novel disease-relevant gene, potentially suitable for the development of new therapeutic strategies.