APOE and Alzheimer disease: Further study of trafficking in hiPSC-derived astrocytes has established a compensatory functional connection between APOE ε4 and another AD risk factor, PICALM: although APOE ε4 expression was shown to cause defects in early endosomes that disrupted endocytic trafficking in astrocytes, increasing expression of PICALM was able to rescue the system (Narayan et al, 2020).