In the oocyte, key events that trigger the development of primary follicles seem to be the activation of specific transcription factors, such as NOBOX and SOHLH1/SOHLH2 together with LHX8. KO mice of these genes present with hypergonadotropic hypogonadism: in female Nobox-/- fibrous tissues replace follicles (205), while in female Sohlh1-/- and Lhx8-/- infertility is respectively caused by gonadal dysgenesis (206), and early oocytes loss (207). This evidence concerns the gene SOHLH2 and Infertility.