Multiple roles of TDP-43 in gene expression, splicing regulation, and human disease.

TDP-43 is a RNA/DNA binding protein that structurally resembles a typical hnRNP protein family member and displays a significant specificity for binding the common microsatellite region (GU/GT)n. Initially described as a regulator of HIV-1 gene expression, it has been reported in the past to affect both normal and pathological RNA splicing events. In particular, it has been shown to play a fundamental role in the occurrence of several monosymptomatic/full forms of Cystic Fibrosis caused by pathological skipping of CFTR exon 9 from the mature mRNA. Recently, and in a way probably unrelated to splicing, a hyperphosphorylated form of TDP-43 has also been found to accumulate in the cytoplasm of neuronal cells of patients affected by fronto temporal lobar degenerations. In addition to its role in transcription and splicing regulation, a growing body of evidence indirectly suggests that TDP-43 may be involved in other cellular processes such as microRNA biogenesis, apoptosis, and cell division. The aim of this work is to provide the basic facts about TDP-43 an assessment of the multiple functions ascribed to this protein.