These included mechanistic target of rapamycin (MTOR), a potential target for therapy in HD, H2A histone family member Y (H2AFY), a gene whose transcript levels have been recently reported to mark HD activity in human and mouse, CDC-like kinase 3 (CLK3) another gene from the top 99 genes from the previous study, and aquaporin 9 (AQP9), a gene that has been described as a potential biomarker in blood.8, 9, 19. The gene discussed is AQP9; the disease is Huntington disease.