SMAD transcription factors are altered in cell models of HD and regulate HTT expression

- Dysregulation of TGFβ signalling is identified in mouse and human cell models of Huntington's disease.
- Characterisation of this dysregulation in downstream SMAD transcription factors is presented.
- SMAD3 binds to the HTT promotor and can regulate HTT expression in the absence of a CAG expansion.

Transcriptional dysregulation is observable in multiple animal and cell models of Huntington's disease, as well as in human blood and post-mortem caudate. This contributes to HD pathogenesis, although the exact mechanism by which this occurs is unknown. We therefore utilised a dynamic model in order to determine the differential effect of growth factor stimulation on gene expression, to highlight potential alterations in kinase signalling pathways that may be in part responsible for the transcriptional dysregulation observed in HD, and which may reveal new therapeutic targets. We demonstrate that cells expressing mutant huntingtin have a dysregulated transcriptional response to epidermal growth factor stimulation, and identify the transforming growth factor-beta pathway as a novel signalling pathway of interest that may regulate the expression of the Huntingtin (HTT) gene itself. The dysregulation of HTT expression may contribute to the altered transcriptional phenotype observed in HD.