RNA and Protein Interactors with TDP-43 in Human Spinal-Cord Lysates in Amyotrophic Lateral Sclerosis.

The TAR DNA-binding protein of 43 kDa (TDP-43) is a dual function RNA- and DNA-binding protein with varied cellular functions. In degenerating motor neurons in amyotrophic lateral sclerosis (ALS), TDP-43 relocalizes from the nucleus to the cytosol, where it is sequestered into inclusions. It is likely that the pathogenic role of TDP-43 in ALS can involve either a gain or a loss of function, depending on the nature of its RNA or protein interactor. However, while TDP-43 binding partners have been identified in a range of model systems and from the human brain, interactors from human spinal-cord tissue have not. In this study, we have characterized both protein and RNA TDP-43 interactors from neuropathologically normal (control) and ALS-affected ventral lumbar spinal cord, including sporadic ALS (sALS) and familial cases harboring either a A4T mutant SOD1 or a 3' UTR *c.41G>A mutant FUS/TLS or expressing pathological c9orf72 expanded repeats. RNA interactors with TDP-43 were similar between the control and ALS spinal cords examined regardless of genotype. In contrast, protein interactors with TDP-43 did demonstrate differences, with the sALS and mtSOD1 harboring cases examined differing from the protein interactors identified in the FUS 3' UTR mutation and c9orf72 repeat-positive cases.