Transcriptome analysis of the hypothalamus and pituitary of turkey hens with low and high egg production

Authors: Diehl, Kristen; LIU, HSIAO-CHING - North Carolina State University; HICKS, JULIE - North Carolina State University; Long, Julie; PORTER, TOM - University Of Maryland

Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/10/2020
Publication Date: 9/21/2020
Citation: Brady, K.M., Liu, H., Hicks, J.A., Long, J.A., Porter, T.E. 2020. Transcriptome analysis of the hypothalamus and pituitary of turkey hens with low and high egg production. Biomed Central (BMC) Genomics. https://doi.org/10.1186/s12864-020-07075-y.
DOI: https://doi.org/10.1186/s12864-020-07075-y

Interpretive Summary: Turkey hens have the capacity to lay an egg on a daily basis (every 24 to 26 hours or 6-7 eggs/week); however, there are hens that routinely produce fewer eggs (3-4 eggs per week). Understanding the mechanism of why low egg producing hens (LEPH) ovulate less frequently than high egg producing hens (HEPH) is important to improve reproduction in commercial operations. Ovulation in birds is trigged by a preovulatory surge of two hormones, luteinizing hormone (LH) and progesterone, produced by the pituitary and the ovary, respectively. Cells from the pituitary and the ovary were cultured and treated with hormones known either to stimulate or inhibit LH and progesterone production. Gene expression analysis of the cultured cells from HEPH showed up-regulation of genes associated with ovulation stimulation, whereas LEPH cells showed up-regulation of genes associated with inhibition of ovulation. These findings indicate that differences in egg production among turkey hens likely involve differential responsiveness of the cells within the hypothalamo-pituitary-gonadal axis.

Technical Abstract: Low egg producing hens (LEPH) ovulate less frequently than high egg producing hens (HEPH). Ovulation in birds is trigged by a preovulatory surge of luteinizing hormone (LH) and progesterone. Pituitary gonadotroph production of LH is stimulated by gonadotropin releasing hormone (GNRH) and inhibited by gonadotropin inhibitory hormone (GNIH). Granulosa cells from the largest follicle (F1G) respond to LH to produce progesterone while small white follicle cells (SWF) respond to follicle stimulating hormone (FSH) to produced estradiol. Pituitary cells from LEPH and HEPH were subjected to both GNRH and GNIH treatment followed by expression analysis of mRNA levels for HPG axis genes related to ovulation. Additionally, F1G and SWF from LEPH and HEPH were subjected to LH and FSH treatment, respectively, followed by radioimmunoassays for progesterone and estradiol production. Results were analyzed by a two-way ANOVA using the mixed models procedure of SAS. In response to GNRH and GNIH treatment, HEPH pituitary cells showed up-regulation of genes associated with ovulation stimulation, whereas LEPH cells showed up-regulation of genes associated with inhibition of ovulation. HEPH F1G and SWF cells displayed a higher sensitivity and responsiveness to LH and FSH treatment, respectively. Level of egg production impacted ovulation related gene expression in pituitary cells after neuropeptide treatment as well as steroid hormone production of F1G and SWF cells after gonadotropin treatment, with HEPH displaying a greater positive response stimulation. These findings indicate that differences in egg production among turkey hens likely involve differential responsiveness of the cells within the hypothalamo-pituitary-gonadal axis.