RNA was isolated using the miRNeasy Micro Kit (Qiagen) and RNA integrity was assessed by obtaining a RIN score on the Agilent 2100 Bioanalyzer. All of the RNA samples had a RIN > 8. Total RNAs were amplified, labeled and hybridized on HumanHT-12 v4 Expression BeadChips (Illumina) according to the manufacturer’s protocol. Microarray data was analyzed with custom R scripts calling Bioconductor (http://www.bioconductor.org/) packages. Briefly, outlier arrays were detected based on low inter-sample correlations. Raw expression data was log2 transformed, and quantile normalized. Probes were considered robustly expressed if the detection P value was <0.05 for at least half of the samples in the data set. Regional brain and temporal identify of the cells was assessed using CoNTExt (http://context.semel.ucla.edu/).
