Identification and characterization of the changed transcripts in cumulus cells of Bmp15-/- and Bmp15-/-Gdf9+/--DM mice.

Mouse oocytes control cumulus cell metabolic processes that are deficient in the oocytes themselves and this delegation is necessary for oocyte development. Oocyte-derived bone morphogenetic factor 15 (BMP15) and growth differentiation factor 9 (GDF9) appear to be key regulators of follicular development. The effect of these factors on cumulus cell function before the preovulatory surge of luteinizing hormone (LH) was assessed by analysis of the transcriptomes of cumulus cells from wildtype (WT), Bmp15-/-, and Bmp15-/- Gdf9+/- double mutant (DM) mice using microarray analysis. The biological themes associated with the most highly-affected transcripts were identified using bioinformatic approaches, IPA and GenMAPP/MAPPFinder. There were 5,332, 7,640, and 2,651 transcripts identified to be significantly changed in the comparisons of Bmp15-/- vs. WT, DM vs. WT, and DM vs. Bmp15-/- respectively by the criteria of FC (fold change) p <0.01. Among theses changed transcripts, 744 were commonly changed in all three pair-wise comparisons, and hence were considered to be the most highly affected transcripts by mutation of Bmp15 and Gdf9. IPA Analyses revealed that metabolism was the major theme associated with the most highly-changed transcripts: glycolysis and sterol biosynthesis were the two most significantly affected pathways. Most of the transcripts encoding enzymes for sterol biosynthesis were down-regulated in both mutant cumulus cells and in WT cumulus cell after oocytectomy. Similarly, there was a reduction of de novo-synthesized cholesterol in these cumulus cells. This suggests that oocytes regulate cumulus cell metabolism, particularly sterol biosynthesis, by promoting the expression of corresponding transcripts. Furthermore, in WT-mice, Mvk, Pmvk, Fdps, Sqle, Cyp51, Sc4mol, and Ebp, which encode enzymes in the sterol biosynthetic pathway, were found to be expressed robustly in cumulus cells, but expression was barely detectable in oocytes. Levels of de novo-synthesized cholesterol were significantly higher in cumulusenclosed oocytes than denuded oocytes. These results indicate that mouse oocytes are deficient in their ability to synthesize cholesterol and require cumulus cells to provide them with products of the sterol biosynthetic pathway. Oocyte-derived BMP15 and GDF9 may promote this metabolic pathway in cumulus cells as compensation for their own deficiencies.

9

Su YQ, Sugiura K, Wigglesworth K, O'Brien MJ, Affourtit JP, Pangas SA, Matzuk MM, Eppig JJ