Chen et al. [21] conducted microarray analysis of 3 BPD and 3 control iPSCs and neurons derived from these iPSCs. Although our GO annotations, derived from DEGs in iPSCs versus neurons, are similar to those reported by Chen et al, we did not see a major overlap in DEGs in BPD neurons compared to control between the two studies. A key reason for this underlying discrepancy may be the fact that Chen et al. conducted microarray analysis on neurons differentiated for 8 weeks, whereas ours were differentiated for 4 weeks. Alternatively the genetic heterogeneity of BPD revealed by GWAS [45,60] and, more recently, WGS [8,44] studies may underlie this lack of overlap. Our samples were derived from an Old Order Amish pedigree, whereas Chen et al. studied iPSCs reprogrammed from Caucasian donors from unrelated patients and controls. Madison et al [22] reported seeing differential gene expression as early as the NP stage between BPD and control population. This discrepancy might be due to their use of an enriched NP population (CXCR4+) or the different analytical platforms employed. RNA-seq has a
