Transcriptome profiling of wild type primordial germ cells (PGC) by RNAseq

Purpose: To identify molecular pathways underlying epigenetic reprogramming in early germ cell precursors, we examined global gene expression of wild type primordial germ cells using mRNA sequencing. Methods: Given the limited number of PGCs collected from E9.5 to E13.5 (ranging from 300 to 5000), we used a low-input RNA sequencing method, Smart-Seq. RNA libraries were pooled and sequenced by Illumina Hiseq. Results: We generated >22 million uniquely mapped reads per sample and identified >10 thousand transcripts per genotype (RPKM>0.1). Hierarchical clustering and correlation analysis on gene expression indicates samples were clearly separated according to their genotypes with Spearman correlation coefficient of 0.98/0.99 within biological replicates. Compared with E9.5 PGCs, 479 genes were significantly up-regulated and 248 genes were down-regulated in E11.5 PGCs. When compared with E11.5 PGCs, male E13.5 PGCs had 362 up-regulated, and 239 down-regulated genes, whereas female E13.5 PGCs had 1163 up-regulated and 333 down-regulated genes. Overall, the number of up-regulated genes was greater than that of the down-regulated genes in every comparison, suggesting that gene expression is generally activated during PGC reprogramming. Overall design: mRNA profiles of primordial germ cells derived from developmental embryos stages (E9.5, E11.5 and E13.5) were generated by deep sequencing, in duplicates (E9.5 and E11.5) or triplicates (E13.5f and E13.5m), using Illumina Hiseq.