Figure 2: Alteration in the mRNA expression of piRNA pathway genes in the caput epididymidis of aged Gpx5-/- mice. (a) GSEA analysis result of the piRNA pathway genes. A positive ES with a significant P value and FDR indicates higher mRNA levels of piRNA pathway genes in the WT group and the significant downregulation in the Gpx5-/- mice. (b) RNA-seq data validation by RT-qPCR of six known piRNA pathway genes in the 13-month-old WT and Gpx5-/- groups. Quantitative PCR data are presented as mean ± s.d. from three independent animals. NS: not significant;*P < 0.05;**P < 0.01; Student's t-test. GSEA: gene set enrichment analysis; ES: enrichment score; FDR: false discovery rate; RT-qPCR: quantitative reverse transcription PCR; Gpx5: glutathione peroxidase 5; s.d.: standard deviation; WT: wild-type; KO: knockout; NES: normalized enrichment score; piRNA: P-element-induced wimpy testis (PIWI)-interacting RNA.