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The abundance of miR-1b-3p in the chicken ovary is greater after sexual maturation. In the present study there was assessment of whether a single nucleotine polymorphism (SNP) led to an alteration in expression of reproductive traits. The miR-1b-3p abundance was greatest in ovarian follicles The SNP site of rs737028527 (G > A), located in the 734 bp upstream region of pre-miR-1b-3p, was identified in three different chicken breeds. Results from an association analysis of chicken egg-laying traits indicated the SNP was associated with age at first egg production (AFE) and egg number at 32 and 48 weeks (E32, E48; P < 0.01). Hens with genotype AA had an earlier AFE and greater E32 and E48 than hens with other genotypes. The abundance of mature miR-1b-3p in the hens with the GG genotype was larger than those with the AA genotype (P < 0.01), and the luciferase activity of GG genotype promoter was also greater in birds with the AA than GG genotype (P < 0.05). There was inhibition of the production of the transcription factor bound by the specificity protein 1 (Sp1) as a result of the G-to-A mutation, and the luciferase activity of the GG, but not AA, genotype was markedly increased by Sp1. In conclusion, the SNP, rs737028527 (G> A), affected the abundance of mature miR-1b-3p by Sp1 and was associated with chicken egg-laying traits. Data from the present study allow for an increased understanding of the functions and regulation of miR-1b-3p in ovarian follicle development of hens., Competing Interests: Declaration of Competing Interest All authors agreed with the final version of the manuscript and all aspects of the work., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Duck eggs are highly nutritious, and demand for consumption has markedly increased in the growing human population, resulting in the need to increase production. Egg production is dependent on the reproductive performance of animals, a trait that is not highly heritable. Improving reproductive performance, therefore, is an essential aim of breeders performing genetic selection to increase egg production. The ovary has received much attention by breeders because of its importance in the production and release of eggs. The ovary, therefore, has been intensely studied to identify the candidate genes and the polymorphisms associated with egg-laying traits. The expression of these genes in the ovary indicates the potential for involvement in ovarian follicular development. The expression of the growth hormone, follicle-stimulating hormone receptor, prolactin, ovoinhibitor, melatonin receptor, and insulin-like growth factor-2 genes in the ovary has been studied, and polymorphisms have been identified that are related to egg-laying traits. The single nucleotide polymorphisms of these genes help with the identification of novel genetic markers that assist in selecting the ducks with the most desirable genotypes for egg production. This approach to genetic selection is more effective than the traditional method used to select animals for egg production. With this review, therefore, there is a summarization of genetic effects of polymorphisms in candidate genes related to ovarian development and egg production traits in ducks., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Egg production is determined by the function of ovary and is regulated by the hypothalamic-pituitary-ovary axis. The mechanism by which the ovary regulates egg production, however, is still poorly understood. The purpose of this study is to compare the transcriptome difference in ovary of relatively greater and lesser egg producing chickens, and to screen candidate genes related to egg production. A RNA sequencing was performed to analyze and compare the mRNA in ovarian tissues of relatively greater and lesser egg producing chickens. A total of 4 431 new genes expressed in the chicken ovary were mined. There were 305 differentially expressed genes (DEGs) identified between the relatively greater and lesser egg producing hens. Gene ontology analysis identified five candidate genes related to egg production, including ZP2, WNT4, AMH, IGF1, and CYP17A1 genes. Tissue expression profiles indicated these five candidate genes were highly expressed in chicken ovarian tissues, indicating a potential role in regulating chicken ovarian function and egg production. The KEGG analysis indicated the neuroactive ligand-receptor interaction pathway might have an important function in regulation of egg production. In addition, four known pathways related to reproduction were detected, including the calcium signaling, wnt signaling pathway, focal adhesion, and cytokine-cytokine receptor interaction pathways. Results of the present study indicate gene expression differences in the ovarian tissues of relatively greater and lesser egg producing chickens, and identified five important candidate genes related to egg production, which provided a theoretical basis for improving egg production of Jinghai Yellow Chickens., (Copyright © 2019. Published by Elsevier B.V.)

MicroRNAs (miRNAs) are a class of endogenous non-coding RNAs that have an important role in post-transcriptional regulation. Previous analysis of the chicken ovary transcriptome indicated there was a differential abundance of miR-26a-5p in sexually mature and immature hens. In this study, ten single nucleotide polymorphism (SNP) sites in miR-26a-5p primary transcripts (pri-miR-26a-5p) were identified using Sanger sequencing on PCR products in three chicken breeds, among which, the rs316365438(C > T)SNP was associated with age at first egg (AFE) and total number of eggs at 32 weeks (E32). The hens with the TT genotype of the rs316365438(C > T)SNP had an earlier AFE and greater E32 than those with CC and CT genotypes. Due to the presence of linkage disequilibrium (LD) in SNPs, there were only two dominant haplotypes. The two dominant haplotypes with different free-energy and secondary structure were identified and the overexpression vectors were constructed. Overexpression of mature miR-26a-5p from TCTACGCACG haplotype was greater than that from the TTTATATACA haplotype. In summary, the polymorphisms of pri-miR-26a-5p are associated with chicken egg production traits and affect the transcript abundance of the mature miR-26a-5p., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The aim of the study was to evaluate changes in laying patterns depending on the age of different genotypes of laying hens. In the experiment, six genotypes were evaluated (brown-egg hens Bovans Brown, Bovans Sperwer and Isa Sussex, white-egg hens Dekalb White, and laying hens with tinted shells Moravia Barred and Moravia BSL) in three periods during the laying cycle (the onset of lay between 20 and 26 weeks of age, the middle from 36 to 42 weeks of age and the end of lay between 64 and 70 weeks of age). A significant interaction between genotype and age was apparent in mean sequence length (P<0.001), length of the prime sequence (P<0.001), mean number of sequences (P<0.001) and mean time of oviposition (P˂0.001). The longest lag during the course of the experiment was with Moravia BSL, which was more than 3h; the shortest lag was observed in Bovans Brown, which was less than 1h. The mean time of oviposition was also affected by genotype (P˂0.001). Bovans Brown laid their eggs approximately 3.5h after the lights came on, whereas Moravia BSL laid their eggs almost 6h after the lights came on. Egg weight increased with age (P˂0.001), and the smallest differences in egg weight were with ISA Sussex (5g), whereas the biggest differences were with Moravia BSL (10g)., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The reproductive system of a female bird is responsible for egg production. The genes highly expressed in oviduct are potentially important. From RNA-seq analysis, C2H9orf152 (an orthologous gene of human C9orf152) was identified as highly expressed in chicken uterus. To infer its function, we obtained and characterized its complete cDNA sequence, determined its spatiotemporal expression, and probed its transcription factor(s) through pharmaceutical approach. Data showed that the complete cDNA sequence was 1468bp long with a 789bp of open reading frame. Compared to other tested tissues, this gene was highly expressed in the oviduct and liver tissues, especially uterus. Its expression in uterus was gradually increased during developmental and reproductive periods, which verified its involvement in the growth and maturity of reproductive system. In contrast, its expression was not significant different between active and quiescent uterus, suggesting the role of C2H9orf152 in reproduction is likely due to its long-term effect. Moreover, based on its 5'-flanking sequence, Foxd3 and Hnf4a were predicted as transcription factors of C2H9orf152. Using berberine or retinoic acid (which can regulate the activities of Hnf4a and Foxd3, respectively), we demonstrated suppression of C2H9orf152 by the chemicals in chicken primary hepatocytes. As retinoic acid regulates calcium metabolism, and Hnf4a is a key nuclear factor to liver, these findings suggest that C2H9orf152 is involved in liver function and calcium metabolism of reproductive system. In conclusion, C2H9orf152 may have a long-term effect on chicken reproductive system by regulating calcium metabolism, suggesting this gene has an important implication in the improvement of egg production and eggshell quality., (Copyright © 2016 Elsevier B.V. All rights reserved.)

To identify molecular markers and candidate genes associated with reproductive traits, a genome-wide analysis was performed in Jinghai Yellow Chickens to analyze body weight at first oviposition (BWF), age at first oviposition (AFE), weight of the egg at first oviposition (FEW), egg weight at the age of 300 days (EW300), number of eggs produced by 300 days of age (EN300), egg hatchability (HA) and multiple selection index for egg production (MSI). The results showed that seven single nucleotide polymorphisms (SNPs) were associated with reproductive traits (P<1.80E-6, Bonferroni correction). The P-values of the seven SNPs were 5.62E-10, 3.45E-08, 9.76E-07, 8.90E-07, 1.12E-06, 1.42E-07 and 1.48E-07, respectively. These SNPs were located in close proximity to or within the sequence of the five candidate genes, including FAM184B, TTL, RGS1, FBLN5 and PCNX. An additional 46 SNPs that could be associated with reproductive traits were identified (P<3.59E-5, Bonferroni correction). Identification of the candidate genes as well as genome-wide SNPs that may be associated with reproductive traits will greatly advance the understanding of the genetic basis and molecular mechanisms underlying reproductive traits and may have practical significance in breeding programs for the improvements of reproductive traits in the Jinghai Yellow Chicken., (Copyright © 2015 Elsevier B.V. All rights reserved.)

This study investigated the regulatory mechanisms of seasonal breeding, developments of ovarian follicles and incubation in Magang geese, a short day breeding bird. Throughout the year, plasma PRL concentrations increased in non-breeding season in spring and summer (from April to early August), and remained low in the rest of the year, while LH concentrations peaked in August and September and remained low in non-breeding season (March to June). Lengthening photoperiod increased PRL and decreased LH secretions, which inhibited follicular development, terminated lay and induced moulting, while shortening photoperiod decreased PRL and increased LH secretion and reinitiated lay. Long photoperiod stimulated PRL secretion occurred with increased gene expressions of PRL in the pituitary gland and VIP in the hypothalamus, but inhibition of LH secretion was without decreases in gene expressions of LH beta subunit and GnRH. Under breeding conditions, terminating incubation decreased PRL but increased LH concentrations and resumed lay in 24 days following recruitment of about 10 large white follicles into hierarchical development. Plasma concentrations of progesterone and inhibin peaked at peak lay, whereas LH concentrations exhibited a bi-phasic pattern with troughs at peak lay and incubation when PRL concentrations were high. Ninety percent geese exhibited incubation behaviour after laying one clutch of approximately eight eggs in approximately 30 days. In conclusion the seasonal reproductive activities in Magang geese is directly inhibited by long photoperiod and directly stimulated by short photoperiod via PRL and LH secretions, whose interplays also cause occurrences of four to five lay and incubation cycles in the breeding season.

Expression levels of 33 high egg production candidate transcripts in Red-feather Taiwan country chickens (TCCs) were examined by quantitative reverse-transcription (RT) polymerase chain reactions (PCR) in this study. Candidate transcripts were previously identified from a L2-B (L2-subtract-B) hypothalamus/pituitary gland subtractive cDNA library. In this subtractive cDNA library, two divergently selected strains of TCCs, B and L2 were used. These two strains were originated from one single population and were further subjected (since 1982) to the selections of body weight/comb size (B) and eggs to 40wk of age (L2), respectively. Hypothalamuses and pituitary glands that sampled from Red-feather TCCs were previously grouped into high (Red-high; n=20) and low (Red-low; n=20) egg productions based on the rate of lay after 1st egg (hen-day laying rate; %). Rates of lay after 1st egg (mean+/-S.E.) in the Red-high and the Red-low subpopulations were 72.2+/-0.6 and 23.0+/-3.5, respectively (P<0.01). Quantitative RT-PCR validated that 25 candidate transcripts were significantly higher expressed in the Red-high than in the Red-low hens. These transcripts were ANP32A, BDH, CDC42, CNTN1, COMT, CPE, CTNNB1, DIO2, EIF4E, GARNL1, HSPCA, LAPTM4B, MBP, NAP1L4, NCAM1, PARK7, PCDHA@, PGDS, PLAG1, PRL, RAD21, SAR1A, SCG2, STMN1 and UFM1. Among these transcripts, 15 (79.0%), 13 (68.4%), and 12 (63.2%) genes were annotated to involve in cellular physiological process (GO:0050875), metabolism (GO:0008152) and cell communication (GO:0007154). Identified transcripts that related to high egg production are most active in focal adhesion, adherens junction, MAPK signaling, tight junction and cell adhesion pathways.