Blmh deficiency and HHcy dysregulated mTOR signaling/autophagy via increased mTOR promoter occupancy by Phf8-dependent H4K20me1, which caused Aβ accumulation and ultimately impaired cognition and neuro-motor activities. Supported by NCN grants 2016/21/D/NZ4/00478, 2016/23/N/NZ3/01216, 2018/29/B/NZ4/00771, 2019/33/B/NZ4/01760.