Association of single nucleotide polymorphism inmelatonin receptor 1Agene with egg production traits in Yangzhou geese

Association analysis of polymorphisms of candidate genes for laying traits in Yangzhou geese

Egg production is an important economic trait in the Chinese goose industry. Due to the low heritability of annual egg production traits in geese, large-scale individual selection based on annual egg production measurements cannot be carried out. Therefore, new selection methods must be applied for large-scale early selections. To screen for effective molecular markers for early Yangzhou geese selection, the genotypes and gene frequencies of mutated loci of five candidate genes related to egg production, MAGI-1, ACSF2, ASTN2, KIAA1462, and ARHGAP21, were detected and analyzed by PCR-direct sequencing.Furthermore, correlation analysis was performed with annual egg mass and body weight at the point of lay and egg weight, and the results were as follows:Magi-1 (Record-106975)was A > G, ACSF2 (Record-106582)was A > C, ASTN2 (Record-111407)was A > T, KIAA1462 (Record-134172)was A > T, and the base of ARHGAP21 (Record-112359) was G > T. At all the five loci above, the Yangzhou geese population followed the Hardy-Weinberg equilibrium (P > 0.05). The results of the association analysis between different genotypes and production performance showed no significant differences in annual egg production, body weight at the point of lay, and egg weight, among different genotypes (P > 0.05) at the mutation loci of MAGI-1 and ASTN2. At the ACSF2 and KIAA1462, the annual egg production of AC was significantly higher than that of AA and CC (P < 0.05), the annual egg production of TT was significantly higher than that of AA (P < 0.05), and there were no significant differences in body weight at the point of lay and egg weight, among the three genotypes (P > 0.05). At ARHGAP21, the body weight at the lay point of the TT genotype was the highest, which was significantly higher than that of GG (P < 0.05); however, there was no significant difference with the heterozygous GT genotype for this trait (P > 0.05). Therefore, Genotype AC at ACSF2 and genotype TT at KIAA1462 could be used as favorable genotypes for egg production, and genotype TT at ARHGAP21 could be used as a favorable genotype for weight in Yangzhou geese.

TAT gene polymorphism and its relationship with production traits in Muscovy ducks (Cairina Moschata)

In a previous study, the laying pattern of Muscovy duck was explored by macro-fitting the laying curve of Muscovy duck, and transcriptome sequencing technique of the ovarian tissues was used to screen the egg-related gene "TAT." Moreover, recent results have shown that TAT is expressed in organs such as oviduct, ovary, and testis. The objective of this study is to examine the effect of TAT gene on egg production traits of Muscovy ducks. First, the expression levels of TAT gene in highest producing (HP) and lowest producing (LP) in 3 tissues related to reproduction were examined, and the results indicated that the expression of TAT gene in hypothalamus was significantly different between HP and LP groups. Then, 6 SNP loci (g. 120G>T, g, 122G>A, g, 254G> A, g. 270C >T, g, 312G>A, and g. 341C>A) were detected in TAT gene. Further, association analysis between the six SNP loci of TAT gene and egg production traits of 652 individual Muscovy ducks was done. The results showed that g. 254G>A and g. 270C>T were significantly correlated (P < 0.05 or 0.001) with the egg production traits of Muscovy ducks. This study elucidated the molecular mechanism that TAT gene might be regulating the egg production traits of Muscovy ducks.

Polymorphism analysis and expression profile of the estrogen receptor 2 gene in Leizhou black duck

Our previous study on the ovarian transcriptomic analysis in Leizhou black duck revealed that the ESR2 gene was involved in hormone regulation in reproduction and the estrogen signaling pathway related to reproductive performance was enriched. This suggested that ESR2 may have a functional role in the reproductive performance of the Leizhou black duck. Thus, this study aimed at evaluating the polymorphism of the ESR2 gene and its association with egg-laying traits and the distribution pattern of ESR2 mRNA in laying and non-laying Leizhou black ducks. In this study, genomic DNA was extracted from blood samples of 101 Leizhou black ducks to identify single nucleotide polymorphisms (SNPs) of the ESR2 gene to elucidate molecular markers highly associated with egg-laying traits. Four each of laying and non-laying Leizhou black ducks were selected to collect different tissues to analyze the ESR2 gene expression. A total of 23 SNPs were identified and association analysis of the single SNP sites showed that SNPs g.56805646 T>C and exon 3-20G>A were significantly (P < 0.05) associated with egg weight. Ducks with CT and AG genotypes had significantly higher (P < 0.05) egg weights than their respective other genotypes. Haplotype association analysis of g.56805646 T>C and exon 3-20G>A showed that the haplotypes were significantly associated with egg weight. Higher egg weight was seen in individuals with H3H4 haplotypes. In the hypothalamus-pituitary-gonadal (HPG) axis, the results of qRT/PCR showed that ESR2 mRNA was significantly (P < 0.05) expressed in the ovaries of both duck groups than in the hypothalamus and pituitary. In the oviduct, ESR2 was significantly (P < 0.05) higher in the infundibulum and magnum of laying and non-laying ducks respectively. This study provides a molecular marker for selecting Leizhou black ducks for egg production. In addition, it offers theoretical knowledge for studying the related biological functions of the ESR2 gene at the cellular level.

The effect of SNP rs400827589 in exon 2 of the MTNR1B gene on reproductive seasonality and litter size in sheep

In mammals, the melatonin receptor gene has been widely studied since it has a great influence on reproductive traits. However, little is known about the association between polymorphism of the coding region of the MTNR1B gene and year‐round oestrus or the litter size in Small Tail Han sheep. To better understand the effects of single nucleotide polymorphism (SNP) rs400827589 in MTNR1B, a population polymorphism analysis was conducted using genotyping data in 45 sheep breeds around the world. The results indicated that TT was the dominant genotype in all sheep breeds. The associations of this SNP with reproductive seasonality and litter size in Small Tail Han sheep showed rs400827589 was correlated with fecundity as assessed by reproductive seasonality and litter size (p < .05). Bioinformatics analysis indicated the change in amino acid from Ile to Leu may affect the function of the MTNR1B protein by impacting the secondary and tertiary protein structures. The present results demonstrate that rs400827589 could be used in the marker‐assisted selection of the litter size in Small Tail Han sheep.

Polymorphisms of the melatonin receptor 1A gene that affects the reproductive seasonality and litter size in Small Tail Han sheep

Previous researches have shown that MTNR1A plays an essential role in sheep reproduction. However, most researches focused more on the reproductive seasonality of sheep, and few scientists had studied the association of polymorphisms of the MTNR1A gene with ovine litter size and reproductive seasonality. Therefore, we chose MTNR1A gene to detect its novel sequence polymorphisms and population genetics and analyse their association with seasonal reproduction and litter size in ewes. The mRNA expression level in hypothalamus, pituitary and ovary was also detected. In this study, five polymorphisms (g.15118664G > T, g.15118683C > T, g.15118756C > T, g.15118774C > T and g.15118951G > A) were identified in exon 2. Most importantly, the g.15118683C > T and g.15118951G > A were significant difference between year‐round oestrous sheep and seasonal oestrous sheep (p < .01), and g.15118756C > T had a great effect on litter size of Small Tail Han sheep (p < .05). In addition, the mRNA expression level of MTNR1A in the hypothalamus of polytocous Small Tail Han sheep was significantly higher than that in monotocous Small Tail Han sheep (p < .01) and the expression of MTNR1A in the hypothalamus of year‐round oestrous sheep was significantly higher than that in seasonal oestrous sheep (p < .01). Polymorphisms in exon 2 may regulate the reproductive seasonality and litter size of ewes by influencing gene expression to regulate the reproductive seasonality and litter size of ewes. Our studies provided useful guidance in marker‐assisted selection of the litter size in Small Tail Han sheep.

Polymorphisms of melatonin receptor genes and their associations with egg production traits in Shaoxing duck

OBJECTIVE

In birds, three types of melatonin receptors (MTNR1A, MTNR1B, and MTNR1C) have been cloned. Previous researches have showed that three melatonin receptors played an essential role in reproduction and ovarian physiology. However, the association of polymorphisms of the three receptors with duck reproduction traits and egg quality traits is still unknown. In this test, we chose MTNR1A, MTNR1B, and MTNR1C as candidate genes to detect novel sequence polymorphism and analyze their association with egg production traits in Shaoxing duck, and detected their mRNA expression level in ovaries.

METHODS

In this study, a total of 785 duck blood samples were collected to investigate the association of melatonin receptor genes with egg production traits and egg quality traits using a direct sequencing method. And 6 ducks representing two groups (3 of each) according to the age at first eggs (at 128 days of age or after 150 days of age) were carefully selected for quantitative real-time polymerase chain reaction.

RESULTS

Seven novel polymorphisms (MTNR1A: g. 268C>T, MTNR1B: g. 41C>T, and g. 161T>C, MTNR1C: g. 10C>T, g. 24A>G, g. 108C>T, g. 363 T>C) were detected. The single nucleotide polymorphism (SNP) of MTNR1A (g. 268C>T) was significantly linked with the age at first egg (p<0.05). And a statistically significant association (p<0.05) was found between MTNR1C g.108 C>T and egg production traits: total egg numbers at 34 weeks old of age and age at first egg. In addition, the mRNA expression level of MTNR1A in ovary was significantly higher in late-mature group than in early-mature group, while MTNR1C showed a contrary tendency (p<0.05).

CONCLUSION

These results suggest that identified SNPs in MTNR1A and MTNR1C may influence the age at first egg and could be considered as the candidate molecular marker for identify early maturely traits in duck selection and improvement.

Comparative transcriptomic analysis of high and low egg-producing duck ovaries

The egg-laying rate is an important indicator of egg production of laying ducks. Egg production directly impacts the economic benefits of the duck industry. In order to obtain better insight into the molecular mechanisms associated with the process of egg production, comparative transcriptomic analysis of the ovaries of Jinding ducks with high and low egg production was performed using the Illumina HiSeq 2500 system. A total of 843 differentially expressed genes (DEGs) was identified, 367 that were down-regulated and 476 that were up-regulated in high egg production (HEP) ovaries, as compared with low egg production (LEP) ovaries. Some genes, such as MC5R, APOD, ORAI1, and DYRK4, were more active in HEP ovaries, indicating that these genes may play important roles in regulation of egg production. Among these 843 DEGs, 685 were assigned to gene ontology (GO) categories. Of these, 25 genes were related to reproduction, and 30 were related to the reproductive process, including some associated with ovarian follicle development, circadian regulation of gene expression, circadian rhythm, and estrogen receptor binding. Furthermore, some important functional pathways were revealed, such as the steroid biosynthesis pathway, the endocrine and other factor-regulated calcium reabsorption pathways, circadian rhythm, the neuroactive ligand-receptor interaction pathway, fatty acid biosynthesis, and the calcium-signaling pathway, which appear to be much more active in the HEP group, as compared to those of the LEP group. The results of this study provide very useful information that may contribute to future functional studies of genes involved in bird reproduction.

A Functional Mutation in KIAA1462 Promoter Decreases Glucocorticoid Receptor Affinity and Affects Egg-Laying Performance in Yangzhou Geese

The identification of genetic markers is valuable for improving the egg-laying performance in goose production. The single-nucleotide polymorphism (SNP) rs1714766362 in an intron of the goose KIAA1462 gene was found to be relevant to laying performance in our previous study. However, its function remains unclear. In this study, the full-length coding sequence of KIAA1462 gene was firstly characterized in Yangzhou geese. Q-PCR (Quantitative Real Time Polymerase Chain Reaction) results showed that KIAA1462 was highly expressed in the liver, ovary, and mature F1 follicles. For SNP rs1714766362, geese with the AA genotype showed better laying performance than the TT ones and exhibited a higher KIAA1462 expression level in the ovary. Gain- and loss-of function experiments in granulosa cells revealed that KIAA1462 affected the expression of the apoptosis marker gene caspase-3. Considering that rs1714766362 locates in an intron area, we compared the KIAA1462 promoter regions of AA and TT individuals and identified the SNP c.-413C>G (Genbank ss2137504176), which was completely linked to SNP rs1714766362. According to the transcription factor prediction results, the glucocorticoid receptor (GR) would bind to the SNP site containing the C but not the G allele. In this study, we proved this hypothesis by an electrophoretic mobility shift assay (EMSA). In summary, we identified a novel mutation in the promoter of KIAA1462 gene which can modulate GR binding affinity and affect the laying performance of geese.