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

ABSTRACT: BACKGROUND:High egg producing hens (HEPH) show increased hypothalamic and pituitary gene expression related to hypothalamo-pituitary-gonadal (HPG) axis stimulation as well as increased in vitro responsiveness to gonadotropin releasing hormone (GnRH) stimulation in the pituitary when compared to low egg producing hens (LEPH). Transcriptome analysis was performed on hypothalamus and pituitary samples from LEPH and HEPH to identify novel regulators of HPG axis function. RESULTS:In the hypothalamus and pituitary, 4644 differentially expressed genes (DEGs) were identified between LEPH and HEPH, with 2021 genes up-regulated in LEPH and 2623 genes up-regulated in HEPH. In LEPH, up-regulated genes showed enrichment of the hypothalamo-pituitary-thyroid (HPT) axis. Beta-estradiol was identified as an upstream regulator regardless of tissue. When LEPH and HEPH samples were compared, beta-estradiol was activated in HEPH in 3 of the 4 comparisons, which correlated to the number of beta-estradiol target genes up-regulated in HEPH. In in vitro pituitary cell cultures from LEPH and HEPH, thyroid hormone pretreatment negatively impacted gonadotropin subunit mRNA levels in cells from both LEPH and HEPH, with the effect being more prominent in HEPH cells. Additionally, the effect of estradiol pretreatment on gonadotropin subunit mRNA levels in HEPH cells was negative, whereas estradiol pretreatment increased gonadotropin subunit mRNA levels in LEPH cells. CONCLUSIONS:Up-regulation of the HPT axis in LEPH and upstream beta-estradiol activation in HEPH may play a role in regulating HPG axis function, and ultimately ovulation rates. Thyroid hormone and estradiol pretreatment impacted gonadotropin mRNA levels following GnRH stimulation, with the inhibitory effects of thyroid hormone more detrimental in HEPH and estradiol stimulatory effects more prominent in LEPH. Responsiveness to thyroid hormone and estradiol may be due to desensitization to thyroid hormone and estradiol in LEPH and HEPH, respectively, due to up-regulation of the HPT axis in LEPH and of the HPG axis in HEPH. Further studies will be necessary to identify possible target gene desensitization mechanisms and elicit the regulatory role of the HPT axis and beta-estradiol on ovulation rates in turkey hens.

SUBMITTER: Brady K

PROVIDER: S-EPMC7507666 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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

Brady Kristen K Liu Hsiao-Ching HC Hicks Julie A JA Long Julie A JA Porter Tom E TE

BMC genomics 20200921 1

<h4>Background</h4>High egg producing hens (HEPH) show increased hypothalamic and pituitary gene expression related to hypothalamo-pituitary-gonadal (HPG) axis stimulation as well as increased in vitro responsiveness to gonadotropin releasing hormone (GnRH) stimulation in the pituitary when compared to low egg producing hens (LEPH). Transcriptome analysis was performed on hypothalamus and pituitary samples from LEPH and HEPH to identify novel regulators of HPG axis function.<h4>Results</h4>In th ...[more]

PMID: 32957911

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Project description:MicroRNAs exist widely in viruses, plants and animals. As endogenous small non-coding RNAs, miRNAs regulate a variety of biological processes. Tissue miRNA expression studies have discovered numerous functions for miRNAs in various tissues of chicken, but the regulation of miRNAs in chicken pituitary and hypothalamic development related to high and low egg-laying performance has remained unclear.In this study, using high-throughput sequencing technology, we sequenced two tissues (pituitary and hypothalamus) in 3 high- and 3 low-rate egg production Luhua chickens at the age of 300 days. By comparing low- and high-rate egg production chickens, 46 known miRNAs and 27 novel miRNAs were identified as differentially expressed (P?<?0.05). Six differentially expressed known miRNAs, which are expressed in both tissues, were used in RT-qPCR validation and SNP detection. Among them, seven SNPs in two miRNA precursors (gga-miR-1684a and gga-miR-1434) were found that might enhance or reduce the production of the mature miRNAs. In addition, 124 and 30 reciprocally expressed miRNA-target pairs were identified by RNA-seq in pituitary and hypothalamic tissues, respectively and randomly selected candidate miRNA and miRNA-target pairs were validated by RT-qPCR in Jiuyuan black fowl. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway annotation illustrated that a large number of egg laying-related pathways were enriched in the high-rate egg production chickens, including ovarian steroidogenesis and steroid hormone biosynthesis.These differentially expressed miRNAs and their predicted target genes, especially identified reciprocally expressed miRNA-target pairs, advance the study of miRNA function and egg production associated miRNA identification. The analysis of the miRNA-related SNPs and their effects provided insights into the effects of SNPs on miRNA biogenesis and function. The data generated in this study will further our understanding of miRNA regulation mechanisms in the chicken egg-laying process.

Project description:Nutrition during the pre-lay period takes effect on the production performance in the laying flock. This study evaluated the effects of dietary energy and protein levels in pre-lay diet on performance during the whole laying period and the egg quality, bone quality, and mRNA expression of hypothalamus-pituitary-gonadal (HPG) axis-related genes of hens at the end of the laying cycle. A total of 1,856 15-wk old Hy-Line brown pullets were randomly assigned to one of the four dietary treatments: using a 2 × 2 factorial arrangement with 2 energy levels (2,700 and 2,800 kcal/kg ME, respectively) and 2 protein levels (15 and 16.5% CP, respectively). Pullets were fed ad libitum from 15 to 20 wk and from 20 wk onward, fed with a similar laying diet till 72 wk of age. At 72 wk, the expression of genes in the hypothalamus, pituitary, ovarian, and follicles and bone quality was evaluated. At 72wk, there were no differences in production performance, BW, organ index, and ovarian parameters among the dietary treatments. High-CP diet increased the egg shape index and eggshell thickness (p < 0.05), but the eggshell breaking strength, Haugh unit, and albumen height did not differ among the treatments. Neither dietary energy nor protein level took an effect of bone quality. Low-energy diet increased the mRNA expression of gonadotropin-releasing hormone-1 (GnRH-1) in the hypothalamus (p < 0.05). The mRNA expression level of estrogen receptor-1 (ESR-1) in the hypothalamus and ovary was elevated by the 2,700 ME-15%CP diet (p < 0.05). The expression of cytochrome family 17 subfamily A polypeptide 1 (CYP17A1) in the large white follicle (LWF), small yellow follicles (SYF) and dominant follicle (DF) was decreased by the 2,800 kcal/kg diet (p < 0.05). These results indicate that the prelay diet had no influence on the production performance but had minimal effect on the eggshell characteristics and bone parameters. These results suggest that the energy and protein level of the prelay diet changes the expression of HPG axis-related genes of hens around the end of the laying cycle without changing the circulating sex hormone profile. The effect of prelay diet on the endocrinal adjustment at the end of the laying cycle needs to be investigated further.

Dataset Information

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

Publications

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

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