Germ-line specific transcription factor implicated in postnatal oocyte-specific gene expression. Plays a key regulatory role in the expression of multiple oocyte-specific genes, including those that initiate folliculogenesis and those that encode the zona pellucida (ZP1, ZP2 and ZP3) required for fertilization and early embryonic survival. Essential for oocytes to survive and form primordial follicles. The persistence of FIGLA in adult females suggests that it may regulate additional pathways that are essential for normal ovarian development. Binds to the E-box (5'-CANNTG-3') of the ZPs (ZP1, ZP2, ZP3) promoters. Heterodimer with TCF3/isoform E12. Expressed only in the oocytes within the ovary and at lower level in the testis. Found in the resting oocytes of the primordial follicle cells, at the periphery of the ovary and in the hilar region. Also detected in growing oocytes, but at lower levels. Detected as early as embryonic day 13, shortly after the onset of sexual dimorphism of the gonads. Dramatically increases at the end of the embryonic development and peaks at 2 dpp, a time in ovarian development at which oocytes have become enclosed in primordial follicles. Decreases markedly by 7 and 14 days after birth. Persists, but at low level, in adult females. Not detected in male embryos, but detected in adult testes. Females display a defect in the formation of primordial follicles leading to infertility. Although embryonic gonadogenesis appeared normal, primordial follicles were not formed at birth, and massive depletion of oocytes resulted in shrunken ovaries and female sterility. Null females do not express ZP1, ZP2 or ZP3. Since its expression is oocyte-specific in females, Figla is a plausible candidate gene for primary ovarian failure in otherwise phenotypically normal women. The gene for Figla null males have normal fertility.