RNA extraction, RT-PCR and Q-PCR analysis were described before11. To compare the expression level of different genes, probes were normalized to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) by performing 15, 20 and 25 cycles. PCR conditions and cycle numbers were established by using commercially available human fetal brain (single donor, male, 19 weeks of gestation) (Agilent Technologies). Q-PCR was performed by using the Power SYBR Green kit (Applied Biosystems, UK). Primers are listed in Supplementary Table 2.
