Identification and association of novel lncRNA pouMU1 gene mutations with chicken performance traits

Functional SNPs in SYISL promoter significantly affect muscle fiber density and muscle traits in pigs

Our previous studies showed that SYISL is a negative regulator of muscle growth and regeneration in mice, pigs and humans. SYISL knockout resulted in an increase in the density of muscle fibers and muscle growth. However, it is unclear whether there are natural mutations in pig SYNPO2 intron sense-overlapping lncRNA (pSYISL) that affect the expression of pSYISL and muscle growth traits. In this study, three SNPs in exons and six SNPs within the promoter of pSYISL were identified. Association analysis showed that the two SNPs in exons are significantly associated with loin muscle area (p < 0.05); the six SNPs in the promoter that show complete linkage are significantly associated with live backfat thickness and live loin muscle area in American Large White pigs. Bioinformatics and luciferase reporter assays as well as in vitro binding experiments indicated that the mutation of SNP rs702045770 (g.539G>A) leads to the loss of YY1 binding to the promoter, thus affecting the expression level of pSYISL, and we found that Jiangshan Black pigs with genotype GG have a higher expression level of pSYISL than genotype AA individuals, but the muscle fiber density was significantly lower than in genotype AA individuals. Furthermore, the association analysis showed that the carcass backfat thickness of genotype GG of SNP rs702045770 was significantly higher than that of other genotypes in (Pietrain × Duroc) × (Landrace × Yorkshire) crossbred pigs (p < 0.05). The glycolytic potential of genotype GG was significantly higher than that of other genotypes (p < 0.05). These results provide novel insight into the identification of functional SNPs in non-coding genomic regions.

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.

QPCTL Affects the Daily Weight Gain of the F2 Population and Regulates Myogenic Cell Proliferation and Differentiation in Chickens

Molecular breeding can accelerate the process of animal breeding and improve the breeding efficiency. To date, many Indel molecular markers have been identified in livestock and poultry, but how Indels affect economic traits is not well understood. For molecular breeding, it is crucial to reveal the mechanism of action of Indels and to provide more accurate information. The purpose of this study was to investigate how the 52/224-bp multiallelic Indels of the chicken QPCTL promoter area affect the daily weight gain of chickens and the potential regulatory mechanism of the QPCTL gene. The analysis was conducted by association analysis, qPCR, dual-fluorescence assay and Western blotting. The results showed that Indels in the QPCTL promoter region were significantly associated with the daily weight gain in chickens and that QPCTL expression showed a decreasing trend in embryonic breast muscle tissues. Furthermore, QPCTL expression was significantly higher in breast muscle tissues of the AC genotype than in those of the AB and BB genotypes. Based on the transcriptional activity results, the pGL3-C vector produced more luciferase activity than pGL3-A and pGL3-B. In addition, overexpression of QPCTL promoted chicken primary myoblast (CPM) proliferation and inhibited differentiation. The results of this study suggest that Indels in the promoter region of the QPCTL gene may regulate the proliferation and differentiation of CPMs by affecting the expression of QPCTL, which ultimately affects the growth rate of chickens. These Indels have important value for the molecular breeding of chickens, and QPCTL can be used as a candidate gene to regulate and improve chicken growth and development.

LncRNAs in domesticated animals: from dog to livestock species

Animal genomes are pervasively transcribed into multiple RNA molecules, of which many will not be translated into proteins. One major component of this transcribed non-coding genome is the long non-coding RNAs (lncRNAs), which are defined as transcripts longer than 200 nucleotides with low coding-potential capabilities. Domestic animals constitute a unique resource for studying the genetic and epigenetic basis of phenotypic variations involving protein-coding and non-coding RNAs, such as lncRNAs. This review presents the current knowledge regarding transcriptome-based catalogues of lncRNAs in major domesticated animals (pets and livestock species), covering a broad phylogenetic scale (from dogs to chicken), and in comparison with human and mouse lncRNA catalogues. Furthermore, we describe different methods to extract known or discover novel lncRNAs and explore comparative genomics approaches to strengthen the annotation of lncRNAs. We then detail different strategies contributing to a better understanding of lncRNA functions, from genetic studies such as GWAS to molecular biology experiments and give some case examples in domestic animals. Finally, we discuss the limitations of current lncRNA annotations and suggest research directions to improve them and their functional characterisation.

Single Nucleotide Polymorphisms of Porcine lncMGPF Regulate Meat Production Traits by Affecting RNA Stability

lncMGPF is a novel positive regulator of myogenic differentiation, muscle growth and regeneration in mouse, pig, and human. But whether natural mutations within lncMGPF gene regulate animal meat production traits is unclear. In this study, ten single nucleotide polymorphisms (SNPs) of pig lncMGPF (plncMGPF) gene were identified among commercial pig breeds and Chinese local pig breeds. These SNPs are highly linked and constructed into multiple haplotypes, and haplotype ATTCATGTTC (H1) mainly exists in commercial pig breeds while haplotype GCCTGCACCT (H3) is more frequent in Chinese local pig breeds. Association analysis indicated that all SNPs are significantly associated with the backfat thickness and loin muscle area (P < 0.05), respectively, and homologous H1 individuals have higher loin muscle area and lower backfat thickness than H3 pigs. Bioinformatics and functional analysis showed that haplotype H1 has a longer half-life and more stable RNA secondary structure than haplotype H3. plncMGPF haplotype H1 has stronger effects on pig primary myogenic progenitor cells differentiation and muscle growth than haplotype H3. Further experiments showed that two SNPs (rs81403974 and rs325492834) function together to confer plncMGPF stability and function. Our observation suggested that the SNPs in lncMGPF can change the RNA stabilities and lncMGPF function, thereby affecting the porcine meat production traits.

Novel 61-bp Indel of RIN2 Is Associated With Fat and Hatching Weight Traits in Chickens

The Ras and Rab interactor 2 (RIN2) gene, which encodes RAS and Rab interacting protein 2, can interact with GTP-bound Rab5 and participate in early endocytosis. This study found a 61-bp insertion/deletion (indel) in the RIN2 intron region, and 3 genotypes II, ID, and DD were observed. Genotype analysis of mutation sites was performed on 665 individuals from F₂ population and 8 chicken breeds. It was found that the indel existed in each breed and that yellow feathered chickens were mainly of the DD genotype. Correlation analysis of growth and carcass traits in the F₂ population of Xinghua and White Recessive Rock chickens showed that the 61-bp indel was significantly correlated with abdominal fat weight, abdominal fat rate, fat width, and hatching weight (P < 0.05). RIN2 mRNA was expressed in all the tested tissues, and its expression in abdominal fat was higher than that in other tissues. In addition, the expression of the RIN2 mRNA in the abdominal fat of the DD genotype was significantly higher than that of the II genotype (P < 0.05). The transcriptional activity results showed that the luciferase activity of the pGL3-DD vector was significantly higher than that of the pGL3-II vector (P < 0.01). Moreover, the results indicate that the polymorphisms in transcription factor binding sites (TFBSs) of 61-bp indel may affect the transcriptional activity of RIN2, and thus alter fat traits in chicken. The results of this study showed that the 61-bp indel was closely related to abdominal fat-related and hatching weight traits of chickens, which may have reference value for molecular marker-assisted selection of chickens.

Transcriptome Analysis Reveals the Profile of Long Non-coding RNAs During Chicken Muscle Development

The developmental complexity of muscle arises from elaborate gene regulation. Long non-coding RNAs (lncRNAs) play critical roles in muscle development through the regulation of transcription and post-transcriptional gene expression. In chickens, previous studies have focused on the lncRNA profile during the embryonic periods, but there are no studies that explore the profile from the embryonic to post-hatching period. Here, we reconstructed 14,793 lncRNA transcripts and identified 2,858 differentially expressed lncRNA transcripts and 4,282 mRNAs from 12-day embryos (E12), 17-day embryos (E17), 1-day post-hatch chicks (D1), 14-day post-hatch chicks (D14), 56-day post-hatch chicks (D56), and 98-day post-hatch chicks (D98), based on our published RNA-seq datasets. We performed co-expression analysis for the differentially expressed lncRNAs and mRNAs, using STEM, and identified two profiles with opposite expression trends: profile 4 with a downregulated pattern and profile 21 with an upregulated pattern. The cis- and trans-regulatory interactions between the lncRNAs and mRNAs were predicted within each profile. Functional analysis of the lncRNA targets showed that lncRNAs in profile 4 contributed to the cell proliferation process, while lncRNAs in profile 21 were mainly involved in metabolism. Our work highlights the lncRNA profiles involved in the development of chicken breast muscle and provides a foundation for further experiments on the role of lncRNAs in the regulation of muscle development.

Effects and Molecular Mechanism of Single-Nucleotide Polymorphisms of MEG3 on Porcine Skeletal Muscle Development

Maternally expressed gene 3 (MEG3) is a long non-coding RNA that is a crucial regulator of skeletal muscle development. Some single-nucleotide polymorphism (SNP) mutants in MEG3 had strong associations with meat quality traits. Nevertheless, the function and mechanism of MEG3 mutants on porcine skeletal muscle development have not yet been well-demonstrated. In this study, eight SNPs were identified in MEG3 of fat- and lean-type pig breeds. Four of these SNPs (g.3087C > T, g.3108C > T, g.3398C > T, and g.3971A > C) were significantly associated with meat quality and consisted of the CCCA haplotype for fat-type pigs and the TTCC haplotype for lean-type pigs. Quantitative real-time PCR results showed that the expression of MEG3-TTCC was higher than that of MEG3-CCCA in transcription level (P < 0.01). The stability assay showed that the lncRNA stability of MEG3-TTCC was lower than that of MEG3-CCCA (P < 0.05). Furthermore, the results of qRT-PCR, Western blot, and Cell Counting Kit-8 assays demonstrated that the overexpression of MEG3-TTCC more significantly inhibited the proliferation of porcine skeletal muscle satellite cells (SCs) than that of MEG3-CCCA (P < 0.05). Moreover, the overexpression of MEG3-TTCC more significantly promoted the differentiation of SCs than that of MEG3-CCCA (P < 0.05). The Western blot assay suggested that the overexpression of MEG3-TTCC and MEG3-CCCA inhibited the proliferation of SCs by inhibiting PI3K/AKT and MAPK/ERK1/2 signaling pathways. The overexpression of the two haplotypes also promoted the differentiation of SCs by activating the JAK2/STAT3 signaling pathway in different degrees. These data are valuable for further studies on understanding the crucial role of lncRNAs in skeletal muscle development.

A 31-bp indel in the 5' UTR region of GNB1L is significantly associated with chicken body weight and carcass traits

BACKGROUND

G-protein subunit beta 1 like (GNB1L) encodes a G-protein beta-subunit-like polypeptide. Chicken GNB1L is upregulated in the breast muscle of high feed efficiency chickens, and its expression is 1.52-fold that in low feed efficiency chickens. However, no report has described the effects of GNB1L indels on the chicken carcass and growth traits.

RESULTS

This study identified a 31-bp indel in the 5' untranslated region (UTR) of GNB1L and elucidated the effect of this gene mutation on the carcass and growth traits in chickens. The 31-bp indel showed a highly significant association with the body weight at 8 different stages and was significantly correlated with daily gains at 0 to 4 weeks and 4 to 8 weeks. Similarly, the mutation was significantly associated with small intestine length, breast width, breast depth and breast muscle weight. Moreover, DD and ID were superior genotypes for chicken growth and carcass traits.

CONCLUSIONS

These results show that the 31-bp indel of GNB1L significantly affects chicken body weight and carcass traits and can serve as a candidate molecular marker for chicken genetics and breeding programs.

A 51 bp indel polymorphism within the PTH1R gene is significantly associated with chicken growth and carcass traits

Parathyroid hormone (PTH) is a crucial regulator of calcium homeostasis and bone remodeling, and the parathyroid hormone 1 receptor (PTH1R) belongs to a class II G-protein-coupled receptor. PTH activates PTH1R, which mediates catabolic and anabolic processes in the skeleton. However, the functional mechanism of PTH1R has not been thoroughly elucidated in organisms. This study identified a 51 bp indel mutation in the first intron of the PTH1R gene and elucidated the effect of this gene mutation on the growth and carcass traits in chickens. The results indicated that the 51 bp indel was significantly associated with subcutaneous fat thickness, abdominal fat weight, body weight and daily gain over 4-8 weeks. Furthermore, we found that PTH1R gene expression was highest in the kidney and liver tissues, and it showed a trend of decreasing in leg and breast muscle tissues at different embryonic stages. In addition, we examined the expression of the three genotypes of the PTH1R gene in the liver, breast muscle and abdominal fat and found that the II genotype was significantly higher than the DD and ID genotypes. In summary, these findings suggest that the PTH1R gene can serve as a potential molecular marker for chicken breeding.

Review: Long non-coding RNA in livestock

Less than 2% of mammalian genomes code for proteins, but 'the majority of its bases can be found in primary transcripts' - a phenomenon termed the pervasive transcription, which was first reported in 2007. Even though most of the transcripts do not code for proteins, they play a variety of biological functions, with regulation of gene expression appearing as the most common one. Those transcripts are divided into two groups based on their length: small non-coding RNAs, which are maximally 200 bp long, and long non-coding RNAs (lncRNAs), which are longer than 200 nucleotides. The advances in next-generation sequencing methods provided a new possibility of investigating the full set of RNA molecules in the cell. In this review, we summarized the current state of knowledge on lncRNAs in three major livestock species - Sus scrofa, Bos taurus and Gallus gallus, based on the literature and the content of biological databases. In the NONCODE database, the largest number of identified lncRNA transcripts is available for pigs, but cattle have the largest number of lncRNA genes. Poultry is represented by less than a half of records. Genomic annotation of lncRNAs showed that the majority of them are assigned to introns (pig, poultry) or intergenic (cattle). The comparison with well-annotated human and mouse genomes indicates that such annotation is a result of lack of proper lncRNA annotation data. Since lncRNAs play an important role in genomic studies, their characterization in farm animals' genomes is critical in bridging the gap between genotype and phenotype.

Association of single nucleotide polymorphism at long non-coding RNA 8138.1 with duration of fertility in egg-laying hens

A previous genome-wide transcriptional analysis identified long non-coding RNA 8138.1 (lncRNA8138.1) as a candidate gene related to hen duration of the fertility (DF) trait. LncRNA8138.1 gene response to growth factor and reproductive system development suggests it has a vital role in reproduction. In this study, we investigated the lncRNA8138.1 gene sequence in a population of egg-laying hens. The sequence analysis of the lncRNA8138.1 gene containing about 1.6 k nucleotides (nt) was observed with four single nucleotide polymorphisms (SNPs) and 7 nt indel including r.4937159A > G; r.4937219T > C; r.4937258G > C; r.4937318C > G and g.4937319_4937325delinsTGTGTGG. Next, the genomic DNAs from laying hen populations were subjected to polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) to detect a region of 457 bp carrying lncRNA8138.1 r.4937159A > G substitution. Further inspection of the region containing r.4937159A > G mutation revealed three genotypes viz., AA, AG, and GG were observed with respective frequencies of 0.106, 0.607, and 0.287 in laying hen population 1 (P1) (n = 1, 042) and respective frequencies of 0.176, 0.708, and 0.116 in laying hen population 2 (P2) (n = 826). Moreover, to further examining the frequencies of r.4937159A > G genotypes in P1 and P2, and their additive and dominance effects; r.4937159A > G locus was significantly associated with DF-trait in both P1 and P2 (EN: the number of eggs, FN: the number of fertile eggs after a single AI), and DN (the number of days post-insemination until last fertile egg). In testing for additive and dominance effects, additive effect was significant (P < 0.05) in both P1 and P2 for DF-trait, and the dominance effect was significant (P < 0.05) for EN and FN traits, suggesting that r.4937159A > G polymorphism is a potential biomarker for DF-trait. However, the identified novel r.4937159A > G mutation and others require further investigation to confirm phenotypic causality and potential genetic relationships with reproductive traits. Overall, our findings suggest the significance of genetic variation in long non-coding RNAs may assist in future breeding programs to improve selection for prolonged DF-trait.

Two insertion/deletion variants in the promoter region of the QPCTL gene are significantly associated with body weight and carcass traits in chickens

Glutaminyl-peptide cyclotransferase-like (QPCTL) is an isoenzyme of glutaminyl-peptide cyclotransferase (QPCT). QPCTL and QPCT catalyze the formation of N-terminal modified pyroglutamate-fractalkine and the chemokine CCL2. The objective of this study was to investigate the association between insertions/deletions in the chicken QPCTL promoter region with growth traits in chickens. We first detected two insertion/deletion variants of QPCTL via whole-genome resequencing analysis of DNA samples from Xichuan chickens. A total of 1896 individuals from 12 breeds were genotyped for 52- and 224-bp insertions/deletions. We found two novel insertions/deletions in the promoter region of the chicken QPCTL gene and studied their association with chicken body weight and carcass traits. Our findings show that QPCTL can be a molecular marker for chicken genetics and breeding programs.

Association Between the Methylation Statuses at CpG Sites in the Promoter Region of the SLCO1B3, RNA Expression and Color Change in Blue Eggshells in Lushi Chickens

The formation mechanism underlying the blue eggshell characteristic has been discovered in birds, and SLCO1B3 is the key gene that regulates the blue eggshell color. Insertion of an endogenous retrovirus, EAV-HP, in the SLCO1B3 5′ flanking region promotes SLCO1B3 expression in the chicken shell gland, and this expression causes bile salts to enter the shell gland, where biliverdin is secreted into the eggshell, forming a blue shell. However, at different laying stages of the same group of chickens, the color of the eggshell can vary widely, and the molecular mechanism underlying the eggshell color change remains unknown. Therefore, to reveal the molecular mechanism of the blue eggshell color variations, we analyzed the change in the eggshell color during the laying period. The results indicated that the eggshell color in Lushi chickens can be divided into three stages: 20–25 weeks for dark blue, 26–45 weeks for medium blue, and 46–60 weeks for light blue. We further investigated the expression and methylation levels of the SLCO1B3 gene at eight different weeks, finding that the relative expression of SLCO1B3 was significantly higher at 25 and 30 weeks than at other laying weeks. Furthermore, the overall methylation rate of the SLCO1B3 gene in Lushi chickens increased gradually with increasing weeks of egg production, as shown by bisulfite sequencing PCR. Pearson correlation analysis showed that methylation of the promoter region of SLCO1B3 was significantly negatively correlated with both SLCO1B3 expression in the shell gland tissue and eggshell color. In addition, we predicted that CpG5 and CpG8 may be key sites for regulating SLCO1B3 gene transcription. Our findings show that as the level of methylation increases, methylation of the CpG5 and CpG8 sites hinders the binding of transcription factors to the promoter, reducing SLCO1B3 expression during the late period and resulting in a lighter eggshell color.