Abstract
BackgroundIt has been reported that calf oocytes are less developmentally competent than oocytes obtained from adult cows. Bone morphogenetic protein 15 (BMP15) and growth and differentiation factor 9 (GDF9) play critical roles in folliculogenesis, follicular development and ovulation in mammalian ovaries. In the present study, we attempted to compare the expression patterns of BMP15 and GDF9 in the cells of calf and cow ovaries to determine a relationship between the level of these genes and the low developmental competence of calf oocytes.MethodsBovine tissues were collected from 9-11 months-old calves and from 4-6 years-old cows. We characterized the gene expression of BMP15 and GDF9 in calf and adult bovine oocytes and cumulus cells using quantitative real-time reverse transcriptase polymerase chain reaction (QPCR) and in situ hybridization. Immunohistochemical analysis was also performed.ResultsThe expression of BMP15 and GDF9 in cumulus cells of adult ovaries was significantly higher than that in calf ovaries, as revealed by QPCR. GDF9 expression in the oocytes of calf ovaries was significantly higher than in those of the adult ovaries. In contrast, BMP15 expression in the oocytes of calf and adult ovaries was not significantly different. The localization of gene expression and protein were ascertained by histochemistry.ConclusionsOur result showed for the first time BMP15 and GDF9 expression in bovine cumulus cells. BMP15 and GDF9 mRNA expression in oocytes and cumulus cells was different in calves and cows.
Highlights
It has been reported that calf oocytes are less developmentally competent than oocytes obtained from adult cows
Bone morphogenetic protein 15 (BMP15) transcripts were detected in ovarian tissues, but were not detected in any other tissues examined by reverse transcriptase polymerase chain reaction (RT-PCR)
In the antral follicles of calf ovaries, BMP15 and growth and differentiation factor 9 (GDF9) mRNAs were strongly detected in the oocytes (Figure 3A and 3E) and were weakly detected in the cumulus cells
Summary
It has been reported that calf oocytes are less developmentally competent than oocytes obtained from adult cows. Bone morphogenetic protein 15 (BMP15) and growth and differentiation factor 9 (GDF9) play critical roles in folliculogenesis, follicular development and ovulation in mammalian ovaries. We attempted to compare the expression patterns of BMP15 and GDF9 in the cells of calf and cow ovaries to determine a relationship between the level of these genes and the low developmental competence of calf oocytes. It was reported that BMP15 and GDF9 expressed only in oocytes in rodents, but expressed in cumulus and mural granulosa cells as well as in oocytes in goats and pigs [1,3,5]. Hussein et al reported that the addition of exogenous GDF9 and BMP15 to maturing cumulusoocyte complexes (COCs) dramatically increased the yield of blastocysts [19]. They reported that the addition of GDF9 and/or BMP15 antagonist to maturing COCs significantly decreased blastocyst yields, compared to untreated COCs [19]
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