Although cell-autonomous genetic programs pursued by germ and somatic cells are of critical import, intimate interplays between the two cell types are also essential for normal development of the female gonad. Recent studies demonstrate that oocytes play active roles in coordinating the growth and differentiation of somatic cells during folliculogenesis and affect successful outcomes at fertilization and early development. Mouse transgenesis has been particularly useful in defining germ-cell specific genes and their roles in folliculogenesis (eg, Dazla, Figla, Nobox, Sohlh1, Ybx2, Cpeb1, Gdf9), fertilization (eg, Zp1, Zp2, Zp3), and preimplantation embryonic development (eg, Npm2, Zar1, Nalp5, Dppa3). Continued identification of novel oocyte-specific genes and the annotation of their functions will provide additional insight into the genetic pathways regulating ovarian development. The knowledge gained from mouse models will no doubt benefit the understanding of human biology and treatment of reproductive failure.