Gene

Oocyte

Cell biology

Gonocyte

Biology

Oogenesis

Sperm

Cell culture

Retinoic acid

Germ line development

Endocrinology

Germ cell

Genetics

Meiosis

Spermatogenesis

Embryo

Development of the gonads

Internal medicine

Germ

Andrology

Medicine

Ovary

Sertoli cell

Gonad

Biomolecules

Retinoic acid (RA), a derivative of vitamin A, is critical for the production of oocytes and sperm in mammals. These gametes derive from primordial germ cells, which colonize the nascent gonad, and later undertake sexual differentiation to produce oocytes or sperm. During fetal development, germ cells in the ovary initiate meiosis in response to RA, whereas those in the testis do not yet initiate meiosis, as they are insulated from RA, and undergo cell cycle arrest. After birth, male germ cells resume proliferation and undergo a transition to spermatogonia, which are destined to develop into haploid spermatozoa via spermatogenesis. Recent findings indicate that RA levels change periodically in adult testes to direct not only meiotic initiation, but also other key developmental transitions to ensure that spermatogenesis is precisely organized for the prodigious output of sperm. This review focuses on how female and male germ cells develop in the ovary and testis, respectively, and the role of RA in this process.

Retinoic Acid and Germ Cell Development in the Ovary and Testis