Early whole-body mutant huntingtin lowering preserves proteins and lipids important for synapse function and white matter maintenance in the LacQ140 mouse model.

Lowering mutant huntingtin (m HTT ) transcription is a promising approach to treat Huntington's disease (HD). Using a m Htt -inducible mouse model we analyzed m Htt lowering initiated at different ages and sustained for different time-periods. mHTT protein in cytoplasmic and synaptic compartments of the caudate putamen, which is most affected in HD, was reduced 38-52%. Little or no lowering of mHTT occurred in nuclear and perinuclear regions where aggregates formed at 12 months of age. m Htt transcript repression partially or fully preserved select striatal proteins (SCN4B, PDE10A). Total lipids in striatum were reduced in LacQ140 mice at 9 months and preserved by early partial m Htt lowering. The reduction in total lipids was due in part to reductions in subclasses of ceramide (Cer), sphingomyelin (SM), and monogalactosyl diglyceride (MGDG), which are known to be important for white matter structure and function. Lipid subclasses-phosphatidylinositol (PI), phosphatidylserine (PS), and bismethyl phosphatidic acid (BisMePA)-were also changed in LacQ140 mice. Levels of all subclasses other than ceramide were preserved by early m Htt lowering. Our findings suggest that early and sustained reduction in m Htt can prevent changes in levels of select striatal proteins and most lipids but a misfolded, degradation-resistant form of mHTT hampers some benefits in the long term.