Differential genome-wide gene expression profiling of bovine largest and second largest follicles

We tried to classify largest (F1) and second largest follicles (F2) by global gene expression profiles and to identify differentially expressed genes between the follicular groups using combination of microarray and quantitative real-time PCR (QPCR) analysis. F1 (10.7 ± 0.7 mm) and F2 (7.8 ± 0.2 mm) were collected for microarray and QPCR analysis. Global gene expression profiles of each follicle were analyzed by hierarchical cluster analysis and expression profiles of representative 16 genes were confirmed by QPCR analysis. Hierarchical cluster analysis classified the follicles into two clusters by microarray expression profiles. The cluster A was composed of only F2 and was characterized by highly expression of 31 genes including IGFBP5, whereas the cluster B contained only F1 and was predominately expressed 45 genes including CYP19, FSHR and INHA. The QPCR analysis confirmed AMH, CYP19, FSHR, GPX3, PGF, PLA2G1B, SCD and TRB2 were greater in F1 than F2, while CCL2, GADD45A, IGFBP5, PLAUR, SELP, SPP1, TIMP1 and TSP2 were greater in F2 than F1. Expression of stage-specific genes in follicles may be closely associated with its growth or atresia. Several genes identified in this study will provide intriguing candidates for the determinant of follicular growth. Global gene expression of three largest follicles and two second largest follicles were analyzed