This work was funded by the CHDI Foundation, a privately funded non-profit biomedical research organisation exclusively dedicated to discovering and developing therapeutics that slow the progression of HD. For this study CHDI Foundation assisted with the generation of Casp6-deficient mice.
Huntington’s disease (HD) is a late-onset progressive neurodegenerative disorder characterised by irrepressible motor dysfunction, cognitive decline and psychiatric disturbances for which there is no effective disease-modifying treatment. The proteolytic cleavage of huntingtin (HTT) to generate N-terminal fragments has been proposed to be a key aspect of HD pathogenesis. In particular, it has been shown that HTT can be cleaved at amino acid 586 by caspase-6 (CASP6) and that prevention of cleavage at this site is neuroprotective and can rescue HD-related phenotypes in YAC transgenic HD mouse models. To determine the role that CASP6 plays in HTT proteolysis, we evaluated the effects of the genetic ablation of Casp6 in theHdhQ150 knock-in mouse model of HD. Here we show that the loss of CASP6 had no effect on the proteolysis of HTT, and did not modify the pattern of N-terminal HTT fragments that are present in the brains of these animals. Furthermore, we show that CASP6 ablation does not influence the steady-state levels of soluble HTT in the brains of presymptomatic mice. Therefore, we conclude that CASP6 is not necessary for HTT proteolysis in the HdhQ150 mouse model of HD, and that targeting CASP6 as a therapeutic strategy should be approached with caution in the context of this complex disease.
* Corresponding author: Gillian P. Bates, Department of Medical and Molecular Genetics, King’s College London School of Medicine, 8th Floor Tower Wing, Guy’s Hospital, London, SE1 9RT, United Kingdom. Phone: +44 20 7188 3722; Fax: +44 20 7188 2585; Email: firstname.lastname@example.org