274. Brain gene expression changes in MHC Class II genes and Neuropilin 2 associated with the transition from acyclic to cyclic ovarian function in postpartum beef cows

Abstract

The aim was to identify hypothalamic genes associated with transition from acyclic to cyclic ovarian function in postpartum cows. Ovarian status was recorded at slaughter for primiparous Brahman cows (Zebu, Bos indicus) at 27–34 days postpartum and hypothalamic tissue was obtained at the same time. Ovaries were classified as: Ov1 (n = 4), follicles 4–5 mm; Ov2 (n = 4), follicles equal or larger 10 mm without ovulation; Ov3 (n = 4), corpus haemorrhagicum or corpus luteum. Hypothalamic regions were: H1 (SC-POA, APVN, anterior hypothalamic nucleus, anterior portion of the arcuate nucleus, nearby areas of the diagonal band of Broca, and medial septum); H2 (basal hypothalamus-median eminence, ventromedial hypothalamus, posterior portion of the arcuate nucleus, and anterior part of the mammillary body). Gene expression was determined using the Agilent bovine 44k DNA microarray and differential expression (DE) was ascertained by mixed model analysis. Functional clustering of DE genes using DAVID (www.david.abcc.ncifcrf.gov) revealed an enrichment of genes linked with synaptic transmission in H1 and H3 comparing Ov1 and Ov3. Three members of the major histocompatibility complex (MHC) class II gene family (BOLA-DQA1, BOLA-DQA2 and BOLA-DQB) showed a higher expression level in Ov2 than Ov1 in H1 and H2. BOLA-DGA2 and BOLA-DQB were downregulated in Ov3 when comparing Ov2 and Ov3. MHC family members have been associated with plasticity in the brain1. Functional clusters of genes involved in cell-cell adhesion were differentially expressed when comparing Ov1 and Ov2 (H2), and Neutropilin-2 which promotes GnRH neuronal migration2 was upregulated in Ov1. The findings provide preliminary evidence that gene expression related to cellular plasticity within the basal hypothalamus-median eminence is associated with the transition from acyclic to cyclic ovarian function in the postpartum cow. (1) Håvik B et al. 2007 Neuroscience 148:925–36 (2) Cariboni A et al. 2007 TRENDS in Neurosciences 30:638–44