Patient data• Decrease of several phospholipids in brains of APOEε4 carriers (in the context of AD)• In the context of AD: reduced levels of PIP2In vivo studies• In the context of APOE ε4 KI mice: reduced levels of PIP2 and reduced degradation of SYNJ1mRNAGenetic risk factors• Mutations of GBA1• Carriers of APOEε4. Here, GBA1 is linked to Alzheimer disease.