NANOS2 and male infertility: The function of Nanos2 in brain development is unknown, as the Nanos2 knock-out mice were apparently normal except for male infertility [25], and no phenotypic abnormality was reported for Nanos2 transgenic mice, which over-express Nanos2 under the control of Oct4DeltaPE promoter, but the expression was not examined in brain [27].