PHOSPHORYLATION OF HUNTINGTIN N17 DOMAIN IS CELL CYCLE REGULATED AND BECOMES DYSREGULATED IN HUNTINGTON’S DISEASE

Abstract

Huntington’s disease (HD) is a genetic disorder caused by a polyglutamine tract expansion in the huntingtin protein. This unstable expansion causes degeneration of cortical and striatal neurons thus emphasizing studies of post-mitotic neurons. In addition to neurological symptoms, HD is also known to affect peripheral areas of the body which makes studying the developmental aspect necessary for a thorough understanding of the disease. Huntingtin is required for proper mitotic spindle formation and orientation. Our group has previously shown that phosphorylation at critical serine residues, 13 and 16 of huntingtin causes localization to various mitotic structures such as centrosomes, spindle microtubules, and the cleavage furrow suggesting that post-translational modifications of huntingtin play a role in the cell cycle. Here we use biophotonic and biochemical techniques to observe the role of phosphorylated huntingtin in the cell cycle. In mouse striatal cells, we observed phosphorylated huntingtin in different stages of mitosis and saw increased phosphorylation and differential localization of huntingtin as mitosis progressed. We also observed an increase in phosphorylation levels as the cell cycle progressed with immunoblotting assays. These findings can be used to identify huntingtin dependant phases of the cycle which may have relevance to the role of huntingtin during development. Furthermore, the role of huntingtin at the mitotic spindle may translate to other microtubule-related functions with relevance to DNA integrity checkpoints.