PARENT SESSION

(W447) DIFFERENTIAL EXPRESSION OF INTRACELLULAR SIGNALLING MOLECULES IN DOMINANT COMPARED TO SUBORDINATE FOLLICLES DURING DIFFERENT STAGES OF THE FOLLICLE WAVE IN CATTLE.

Forde, Niamh¹, Canty, Mary¹, Zielak, Anna¹, Lonergan, Pat¹, Smith, George², Ireland, James², Evans, Alex¹, ¹ University College Dublin, Dublin, Ireland² Michigan State University, East Lansing, MI

ABSTRACT- Factors that trigger enhanced growth of a dominant follicle from a cohort of growing follicles during a follicular wave are unknown. Since all follicles in an early growing cohort are exposed to similar hormones, we hypothesize that follicles destined to become dominant have enhanced expression of signal transduction factors in granulosa and/or theca cells compared to non-dominant, subordinate follicles. Ovaries were collected from cattle during the first follicular wave and assigned to one of three periods; emergence (n=4; suspected dominant follicle had highest follicular fluid estradiol (FF E2) concentration 12.9±1.0 vs 11.0±0.7 ng/ml), selection (n=4; dominant follicle was largest and had FF E2 concentration that was ≥150% of the next largest follicle; 15.1±6.7 vs 8.8±3.4 ng/ml) and dominance (n=7; dominant follicle was largest and had FF E2 concentration that was ≥200% of the next largest follicle; 72.5±40.3 vs 4.4±1.5 ng/ml). In the two largest follicles, theca and granulosa cells were separated and mRNA for signal transduction factors, previously identified as differentially expressed in dominant vs subordinate follicles using cDNA microarrays, were measured using real-time PCR. At emergence, mRNA in the theca cells for Calcium/Calmodulin-dependent kinase 1 (CAMK 1; P=0.003) and mRNAs in the granulosa cells for aromatase (P=0.002) and cyclophylin (P=0.025) were greater, and mRNA for breast cancer antiestrogen receptor 1 (BCAR1; P=0.039) was lower in dominant compared to subordinate follicles. In the selection group, mRNA for CAMK 1 (P=0.040) in the theca cells and for aromatase (P=0.037) in the granulosa cells were greater in dominant compared to subordinate follicles. In the dominance group, mRNA in the theca cells for CAMK 1 (P=0.028) and Ephrin A4 (P=0.017), and mRNAs in the granulosa cells for aromatase (P=0.027), LH receptor (P=0.029) and BCAR1 (P=0.027) were greater, and mRNA for -glycan (P=0.009) and FGF-1 intracellular binding protein (FIBP; P=0.043) were lower in dominant compared to subordinate follicles. We conclude that dominant follicles have greater expression of signal transduction factors that promote development and reduced expression of signalling factors that hinder development compared to subordinate follicles. (Supported by Science Foundation Ireland)

KEY WORDS: follicle, signal transduction, genomics, cattle