Identification of differentially expressed microRNAs during the development of Chinese murine mammary gland.

MicroRNAs (miRNAs) are endogenous approximately 22 nucleotide-long noncoding RNAs. In this study, to investigate miRNA expression profiles and their functions in mammary gland development, we have used microarray as well as qRT-PCR, to analyze the miRNA expression changes along the murine mammary cycle during pregnancy, particularly on transition from pregnancy to lactation. It shows that every developmental stage of the mammary gland has its own miRNA expression pattern. Compared with virgin and involution, some miRNAs such as miR-138 and miR-431 are downregulated, whereas, some miRNAs such as miR-133 and miR-133a-133b are upregulated during pregnancy and lactation. These results indicate that miRNAs are functionally involved in mammary gland development.