Molecular cloning of a cDNA encoding a bovine growth differentiation factor-9 (GDF-9) and expression of GDF-9 in bovine ovarian oocytes and in vitro-produced embryos.

Growth differentiation factor-9 (GDF-9), a member of the transforming growth factor-beta superfamily, is known to be expressed specifically in ovaries of various mammalian species and to be important for normal follicular development in mice. In the present study, a cDNA encoding for bovine GDF-9 was isolated and characterized, and expression of GDF-9 mRNA in ovarian oocytes and in-vitro-derived embryos was examined. Isolation of bovine GDF-9 was achieved using the polymerase chain reaction (PCR) with primers based on an ovine GDF-9 cDNA sequence. A 1385 bp cDNA encodes a deduced 453-amino acid sequence which contains the proregion (318 residues) and the mature protein (135 residues) portion. The deduced amino acid sequence of bovine GDF-9 is 98 and 93% identical to ovine GDF-9 and human GDF-9 in the mature portion of the molecule, respectively. Results from reverse transcription (RT)-PCR analysis detected bovine GDF-9 mRNA in preantral follicles (150-200 microm in diameter), early antral follicles (400-800 microm in diameter), and immature oocytes, whereas no detectable PCR signal was observed in cumulus/granulosa cells. In addition, bovine GDF-9 mRNA continued to be expressed in developing embryos up to the 8-cell stage, but was undetectable at the blastocyst stage. These findings give rise to new possibilities regarding an additional physiological role of GDF-9 in early embryonic development as well as in the development of follicles.