Peer Review #1 of "Comparison of miRNA expression profiles in pituitary–adrenal axis between Beagle and Chinese Field dogs after chronic stress exposure (v0.1)"

Abstract

MicoRNAs (miRNAs), usually as gene regulators, participate in various biological processes, of which stress response is included. Hypothalamus-pituitary-adrenal axis (HPA axis) is an important pathway in regulating stress response. Although the mechanism that HPA axis regulates stress response has been basically revealed, the knowledge that miRNAs regulate stress response within HPA axis, still remains poor. The object of this study was to investigate the miRNAs in pituitary and adrenal cortex that regulated chronic stress response with high-throughput sequencing. The pituitary and adrenal cortex of Beagle and Chinese Field Dog (CFD) from a stress exposure group [including Beagle pituitary 1 (BP1), CFD pituitary 1 (CFDP1), Beagle adrenal cortex 1 (BAC1), CFD adrenal cortex 1 (CFDAC1)] and a control group [including Beagle pituitary 2 (BP2), CFD pituitary 2 (CFDP2), Beagle adrenal cortex 2 (BAC2), CFD adrenal cortex 2 (CFDAC2)], were selected for miRNA-seq comparisons. Comparisons, that were made in pituitary (including BP1 vs. BP2, CFDP1 vs. CFDP2, BP1 vs. CFDP1 and BP2 vs. CFDP2) and adrenal cortex (including BAC1 vs. BAC2, CFDAC1 vs. CFDAC2, BAC1 vs. CFDAC1 and BAC2 vs. CFDAC2), showed that a total of 39 and 18 common differentially expressed miRNAs (DE-miRNAs) (Total read counts >1000, Fold change >2 & P-value <0.001), that shared in at least two pituitary comparisons and at least two adrenal cortex comparisons, were detected separately. These identified DE-miRNAs were predicted for target genes, thus resulting in 3959 and 4010 target genes in pituitary and adrenal cortex, respectively. Further, 105 and 10 differentially expressed genes (DEGs) (Fold change >2 & P-value <0.05) from those target genes in pituitary and adrenal cortex were obtained separately, in combination with our previous corresponding transcriptome study. Meanwhile, in line with that miRNAs usually negatively regulated their target genes and the dual luciferse reporter assay, we finally identified cfa-miR-205 might play an important role by up-regulating MMD in pituitary and hippocampus, thus enhancing the immune response, under chronic stress exposure. Our results shed light on the miRNA expression profiles in pituitary and adrenal cortex with and without chronic stress exposure, and provide a new insight into miR-205 with its feasible role in regulating chronic stress in pituitary and hippocampus through targeting MMD.