Objective To screen and identify the key miRNAs during mammary gland development and milk secretion of rats. Methods Gene U6 was taken as interior label gene by real time-PCR to compare the differences of expression levels of miR-142-3p and miR-145-3p in the mammary gland, liver, heart, spleen, lung, kidney, ovary and uterus after 21 postpartum. Moreover, the expressions of miR-142-3p and miR-145-3p in different stages (1, 7 and 21 d) of lactation were summarized. Results There was significant difference in miR-142-3p in lactation 21 d between different tissues. The expression of miR-142-3p was significantly higher in mammary gland than that in heart, spleen, lung, kidney, ovary and uterus tissues, which was second only to the expression in liver (P<0.05). The expression of miR-145-3p was significantly higher in mammary gland than that in liver, spleen and kidney. There was no significant difference in the expression of miR-145-3p between heart, lung, ovary and uterus (P>0.05). Furthermore, the relative expression level of miR-142-3p was continuing downward continued to decline in breast at different stages of lactation, while the relative expression level of miR-145-3p was up-regulated after down-regulating. Conclusion miR-142-3p and miR-145-3p are differentially expressed in different tissues and physiological periods in rats. In addition, miR-142-3p can regulate the growth of mammary gland and the formation of lactation by targeting prolactin receptor (Prlr), miR-145-3p may have the same function with miR-145 and miR-145-5p.

PURPOSE: Circular RNAs (circRNAs), a novel class of RNAs, perform important functions in biological processes. However, the role of circRNAs in the mammary gland remains unknown. The present study is aimed at identifying and characterizing the circRNAs expressed in the mammary gland of lactating rats. METHODS: Deep sequencing of RNase R-enriched rat lactating mammary gland samples was performed and circRNAs were predicted using a previously reported computational pipeline. Gene ontology terms of circRNA-producing genes were also analyzed. RESULTS: A total of 6,824 and 4,523 circRNAs were identified from rat mammary glands at two different lactation stages. Numerous circRNAs were specifically expressed at different lactation stages, and only 1,314 circRNAs were detected at both lactation stages. The majority of the candidate circRNAs map to noncoding intronic and intergenic regions. The results demonstrate a circular preference or specificity of some genes. DAVID analysis revealed an enrichment of protein kinases and related proteins among the set of genes encoding circRNAs. Interestingly, four protein-coding genes (Rev3l, IGSF11, MAML2, and LPP) that also transcribe high levels of circRNAs have been reported to be involved in cancer. CONCLUSION: Our findings provide the basis for comparison between breast cancer profiles and for selecting representative circRNA candidates for future functional characterization in breast development and breast cancer.
Animals ; Biological Processes ; Breast ; Breast Neoplasms ; DNA, Intergenic ; Female ; Gene Ontology ; High-Throughput Nucleotide Sequencing ; Introns ; Lactation ; Mammary Glands, Human* ; Phosphotransferases* ; Protein Kinases ; Rats* ; Ribonucleases ; RNA* ; RNA, Untranslated ; Sensitivity and Specificity