Hikabe, O. et al. Nature http://dx.doi.org/10.1038/nature20104 (2016).

The mature oocyte represents a critical resource for studying mammalian development as well as reproduction and fertility. Hikabe et al. now report a culture system for generating fertilization-competent mouse oocytes from fibroblast-derived pluripotent stem cells in about 30 days. The researchers previously showed that it is possible to differentiate mouse pluripotent stem cells into primordial germ-cell-like cells that can become functional oocytes. However, the transformation from germ cell to gamete required transplantation into adult female mice. In their new, fully in vitro method, primordial germ-cell-like cells are cocultured with female gonadal somatic cells, and hormones, inhibitors and other factors are administered at key stages to stimulate the development of a follicular environment and to coordinate stages of the egg cell's maturation.