RNA synthesis in immature mouse oocyte development

Oocyte development in several nonmammalian species is characterized by the synthesis of large quantities of ribonucleic acids during lampbrush stages of meiosis. These are stored in the oocyte and used during later oocyte maturation and early embryogenesis. This autoradiographic study examined the incorporation and persistence of ribonucleic acid in mouse oocytes during comparable stages of development. At each age examined, fetal through juvenile, the radiolabeled RNA precursors were incorporated into mouse oocytes during the growth stages. The RNAase‐digestible label appeared first over nucleoli and meiotic chromosomes, becoming cytoplasmic after 24 hours, and remaining cytoplasmic through all remaining stages. Once incorporated the label persisted during subsequent oocyte growth and maturation through preimplantation embryo stages with apparently undiminished levels. It is suggested that this persistently labeled RNA represents maternal RNA stored for use during early embryonic development.