Essential for female fertility. May play a role in the oocyte-to-embryo transition. Ovary. Expressed in primary oocytes (from primary through antral follicle stages) and during the progression from Meiosis I to Meiosis II. The mRNA is detected in growing oocytes (early primary follicle, type 3a) through fully grown oocytes (antral follicle, type 8). Expressed in zygote at the one-cell embryo, markedly less abundant at the two-cell embryo. Belongs to the ZAR1 family.