Gene expression profiling of differentially expressed genes in granulosa cells of bovine dominant follicles using suppression subtractive hybridization.

Development of antral follicles beyond 3 to 4 mm in cattle appears as a wave pattern that occurs two to three times during the estrous cycle. Each wave presents a cyclic recruitment of multiple follicles at the 3- to 4-mm stage, followed by the selection of a single follicle that becomes the dominant follicle (DF). The molecular determinants involved in the follicular dominance process remain poorly understood. The objective of the current study was to compare gene expression in granulosa cells (GCs) between growing dominant follicles from Day 5 of the estrous cycle and nonselected small follicles (<or=4 mm) using the suppression subtractive hybridization (SSH) approach to identify candidate genes differentially expressed in GCs of the DF. Small follicle cDNAs were subtracted from DF cDNAs (DF-SF) and used to establish a DF GC-subtracted cDNA library. A total of 42 nonredundant cDNAs were identified. Detection of previously identified genes such as CX43, CYP19, INHBA, and SERPINE2 supported the validity of our experimental model and the use of SSH as the method of analysis. For selected genes such as ApoER2, CPD, CSPG2, 14-3-3 epsilon, NR5A2/SF2, RGN/SMP30, and SERPINE2, gene expression profiles were compared by virtual Northern blot or reverse transcriptase-polymerase chain reaction, and results confirmed an increase or induction of their mRNA in GCs of dominant follicles compared with that of small follicles. We conclude that we have identified novel genes (known and unknown) that are up-regulated in bovine GCs that may affect follicular growth, dominance, or both.