CLELLAND, E; KOHLI, G; DIMUCCIO, T; CAMPBELL, R; PENG, C; York University, Toronto; York University, Toronto; York University, Toronto; Woods Hole Marine Science Centre, Woods Hole, Ma.; York University, Toronto: Investigation of Bone Morphogenetic Protein-15 (BMP-15) in Zebrafish Follicles

Bone Morphogenetic Protein-15 (BMP-15) also known as Growth and Differentiation
Factor-9B (GDF-9B) and a related peptide, GDF-9, form a unique subset of the transforming growth factor-&beta (TGF-&beta) cytokines. In mammalian systems, GDF-9 and BMP-15 are secreted from oocytes and are essential for normal growth and development of follicles. However, the role of these growth factors in lower vertebrates has not been examined. In this study, we have cloned BMP-15 from zebrafish and have detected its expression in ovarian follicles. The deduced propeptide is 384 aa in length, possessing a 125 aa mature peptide at the carboxy terminus. The mature peptide is 50-60% homologous to mammalian isoforms and contains the cysteine knot characteristic of TGF-&beta type peptides. It remains in the GDF-9/BMP-15 subset due to the absence of the cysteine residue responsible for the formation of intermolecular disulfide bonds. Quantitative-PCR analysis suggests BMP-15 mRNA is expressed in primary growth stage follicles and expression levels remain essentially unchanged throughout follicle development. These observations were confirmed using in situ hybridization employing DIG-labeled sense and antisense RNA probes. A peptide epitope occurring near the carboxy terminus of the mature peptide was synthesized and used to produce primary antibody (in rabbit). BMP-15 has been localized in follicles using immunohistochemical and immunoblotting techniques. The role of BMP-15 in regulating follicle development in zebrafish awaits further investigation.