miRNAs can control the fertility of female mice

Small molecules known as miRNAs, which are generated naturally by the body, regulate the conversion of genetic information into proteins.

New data, generated by Jiahuai Han and colleagues, at The Scripps Research Institute, La Jolla, have now indicated that miRNAs can control the fertility of female mice.

The generation of miRNAs is a complex process that involves a protein known as Dicer. In the study, mice expressing substantially lower levels of Dicer than normal mice (Dicerd/d mice) were found to have only one defect — the female mice were infertile. Infertility was a result of impaired functioning of the corpus luteum, the structure that forms at the site of release of the fertilized egg and that is required to maintain pregnancy at the early stages. Detailed analysis indicated that the functioning of the corpus luteum was impaired because it was unable to form new blood vessels, and that this was associated with increased expression of the protein TIMP1, which inhibits blood vessel formation. As injection of the miRNAs miR17-5p and let7b into the ovaries of Dicerd/d mice decreased expression of TIMP1 and increased the number of blood vessels in the corpus luteum, the authors concluded that the development and function of the corpus luteum in mice is tightly regulated by miRNAs.