Candidate Gene Expression in Bos indicus Ovarian Tissues: Prepubertal and Postpubertal Heifers in Diestrus

Growth factors such as bone morphogenetic proteins 6, 7, 15, and two isoforms of transforming growth factor-beta (BMP6, BMP7, BMP15, TGFB1, and TGFB2), and insulin-like growth factor system act as local regulators of ovarian follicular development. To elucidate if these factors as well as others candidate genes, such as estrogen receptor 1 ( ), growth differentiation factor 9 ( ), follicle-stimulating hormone receptor ( ), luteinizing hormone receptor ( ), bone morphogenetic protein receptor, type 2 ( ), type 1 insulin-like growth factor receptor ( ), and key steroidogenic enzymes cytochrome P450 aromatase and 3-β-hydroxysteroid dehydrogenase ( and ) could modulate or influence diestrus on the onset of puberty in Brahman heifers, their ovarian mRNA expression was measured before and after puberty (luteal phase). Six postpubertal (POST) heifers were euthanized on the luteal phase of their second cycle, confirmed by corpus luteum observation, and six prepubertal (PRE) heifers were euthanized in the same day. Quantitative real-time PCR analysis showed that the expression of , and mRNA was greater in PRE heifers, when contrasted to POST heifers. The expression of and was lower in PRE heifers. Differential expression of ovarian genes could be associated with changes in follicular dynamics and different cell populations that have emerged as consequence of puberty and the luteal phase. The emerging hypothesis is that and are co-expressed and may modulate the expression of and , and . could influence the downregulation of and upregulation of and , which mediates the follicular dynamics in heifer ovaries. Upregulation of expression prepuberty, compared to postpuberty diestrus, correlates with increased levels and . Thus, and may play synergic roles and were predicted to interact, from the expression data ( = 0.07, = 0.84). The role of these co-expressed genes in puberty and heifers luteal phase merits further research.