Generation of Astrocytes from hiPSCs

hiPSCs were maintained using standard protocols and were differentiated into astrocytes as described previously, generating highly enriched (>90%) populations of astrocytes (Supplementary Figure S1A) (8 (link),11 (link),48–51 (link)). hiPSCs were maintained on Geltrex (Life Technologies) with serum-free Essential 8 Medium media (Life Technologies), and passaged using EDTA. After neural conversion (7 days in a chemically defined medium containing 1 μM Dorsomorphin (Millipore), 2 μM SB431542 (Tocris Bioscience) and 3.3 μM CHIR99021 (Miltenyi Biotec), neural precursors were patterned for 7 days with 0.5 μM retinoic acid and 1 μM purmorphamine, followed by a 4-day treatment with 0.1 μM purmorphamine. After a propagation phase (60–120 days) with 10 ng/ml FGF-2 (Peprotech), astrocytes were terminally differentiated in presence of BMP4 (10 ng/ml, R&D) and LIF (10 ng/ml, Sigma-Aldrich) for 30 days. Informed consent was obtained from all patients and healthy controls in this study. Experimental protocols were all carried out according to approved regulations and guidelines by UCLH’s National Hospital for Neurology and Neurosurgery and UCL’s Institute of Neurology joint research ethics committee (09/0272).