Proteomic analysis of hypothalamic proteins of high and low egg production strains of chickens

The hypothalamic transcriptome reveals the importance of visual perception on the egg production of Wanxi white geese

Egg performance significantly impacts the development of the local goose industry. The hypothalamus plays an essential role in the egg production of birds. However, few potential candidate genes and biological functions related to egg production in geese have been identified in hypothalamus tissue. In this study, 115 geese were raised and observed for 5 months during the laying period. To understand the regulation mechanism of egg production, the hypothalamus transcriptome profiles of these geese were sequenced using RNA-seq. The hypothalamus samples of four high egg production (HEP) and four low egg production (LEP) geese were selected and collected, respectively. A total of 14,679 genes were identified in the samples. After multiple bioinformatics analyses, Gene Ontology (GO) annotations indicated that genes related to egg production were mainly enriched in biological processes of "response to light stimulus," "sensory system development," and "visual perception." Six potential candidate genes (PDE6C, RHO, MFRP, F2, APOB, and IL6) based on their corresponding GO terms and interaction networks were identified. These identified candidate genes can be used as selection markers to improve the egg production of Wanxi white geese. Our study highlights how visual perception may affect the regulation of geese egg production.

Whole transcriptome analysis revealed the regulatory network and related pathways of non-coding RNA regulating ovarian atrophy in broody hens

Poultry broodiness can cause ovarian atresia, which has a detrimental impact on egg production. Non-coding RNAs (ncRNAs) have become one of the most talked-about topics in life sciences because of the increasing evidence of their novel biological roles in regulatory systems. However, the molecular mechanisms of ncRNAs functions and processes in chicken ovarian development remain largely unknown. Whole-transcriptome RNA sequencing of the ovaries of broodiness and laying chickens was thus performed to identify the ncRNA regulatory mechanisms associated with ovarian atresia in chickens. Subsequent analysis revealed that the ovaries of laying chickens and those with broodiness had 40 differentially expressed MicroRNA (miRNAs) (15 up-regulated and 25 down-regulated), 379 differentially expressed Long Noncoding RNA (lncRNAs) (213 up-regulated and 166 down-regulated), and 129 differentially expressed circular RNA (circRNAs) (63 up-regulated and 66 down-regulated). The competing endogenous RNAs (ceRNA) network analysis further revealed the involvement of ECM-receptor interaction, AGE-RAGE signaling pathway, focal adhesion, cytokine-cytokine receptor interaction, inflammatory mediator regulation of TRP channels, renin secretion, gap junction, insulin secretion, serotonergic synapse, and IL-17 signaling pathways in broodiness. Upon further analysis, it became evident that THBS1 and MYLK are significant candidate genes implicated in the regulation of broodiness. The expression of these genes is linked to miR-155-x, miR-211-z, miR-1682-z, gga-miR-155, and gga-miR-1682, as well as to the competitive binding of novel_circ_014674 and MSTRG.3306.4. The findings of this study reveal the existence of a regulatory link between non-coding RNAs and their competing mRNAs, which provide a better comprehension of the ncRNA function and processes in chicken ovarian development.

Addition of NaCl or Sucrose on the Protein Content, and Functional and Physicochemical Properties of Egg Whites Liquid under Heat Treatment

In this study, differences in the protein content and functional and physicochemical properties of four varieties of egg white (EW) were studied by adding 4-10% sucrose or NaCl and then heating them at 70 °C for 3 min. According to a high-performance liquid chromatography (HPLC) analysis, the percentages of ovalbumin, lysozyme and ovotransferrin rose with an increase in the NaCl or sucrose concentration; however, the percentages of ovomucin and ovomucoid decreased. Furthermore, the foaming properties, gel properties, particle size, α-helixes, β-sheets, sulfhydryl groups and disulfide bond content also increased, whereas the content of β-turns and random coils decreased. In addition, the total soluble protein content and functional and physicochemical properties of black bone (BB) chicken and Gu-shi (GS) EWs were higher than those of Hy-Line brown (HY-LINE) and Harbin White (HW) Ews (p < 0.05). Subsequently, transmission electron microscopy (TEM) confirmed the changes in the EW protein structure in the four varieties of Ews. As the aggregations increased, the functional and physicochemical properties decreased. The protein content and functional and physicochemical properties of Ews after heating were correlated with the concentration of NaCl and sucrose and the EW varieties.

Interacting Networks of the Hypothalamic-Pituitary-Ovarian Axis Regulate Layer Hens Performance

Egg production is a vital biological and economic trait for poultry breeding. The 'hypothalamic-pituitary-ovarian (HPO) axis' determines the egg production, which affects the layer hens industry income. At the organism level, the HPO axis is influenced by the factors related to metabolic and nutritional status, environment, and genetics, whereas at the cellular and molecular levels, the HPO axis is influenced by the factors related to endocrine and metabolic regulation, cytokines, key genes, signaling pathways, post-transcriptional processing, and epigenetic modifications. MiRNAs and lncRNAs play a critical role in follicle selection and development, atresia, and ovulation in layer hens; in particular, miRNA is known to affect the development and atresia of follicles by regulating apoptosis and autophagy of granulosa cells. The current review elaborates on the regulation of the HPO axis and its role in the laying performance of hens at the organism, cellular, and molecular levels. In addition, this review provides an overview of the interactive network regulation mechanism of the HPO axis in layer hens, as well as comprehensive knowledge for successfully utilizing their genetic resources.

Transcriptomic analyses of the HPG axis-related tissues reveals potential candidate genes and regulatory pathways associated with egg production in ducks

BACKGROUND

Egg production is one of the most important economic traits in the poultry industry. The hypothalamic-pituitary-gonadal (HPG) axis plays an essential role in regulating reproductive activities. However, the key genes and regulatory pathways within the HPG axis dominating egg production performance remain largely unknown in ducks.

RESULTS

In this study, we compared the transcriptomic profiles of the HPG-related tissues between ducks with high egg production (HEP) and low egg production (LEP) to reveal candidate genes and regulatory pathways dominating egg production. We identified 543, 759, 670, and 181 differentially expressed genes (DEGs) in the hypothalamus, pituitary, ovary stroma, and F5 follicle membrane, respectively. Gene Ontology (GO) analysis revealed that DEGs from four HPG axis-related tissues were enriched in the "cellular component" category. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated that the neuroactive ligand-receptor interaction pathway was significantly enriched based on DEGs commonly identified in all four HPG axis-related tissues. Gene expression profiles and Protein-Protein Interaction (PPI) network were performed to show the regulatory relationships of the DEGs identified. Five DEGs encoding secreted proteins in the hypothalamus and pituitary have interaction with DEGs encoding targeted proteins in the ovary stroma and F5 follicle membrane, implying that they were these DEGs might play similar roles in the regulation of egg production.

CONCLUSIONS

Our results revealed that neuroactive ligand-receptor interaction pathway and five key genes(VEGFC, SPARC, BMP2, THBS1, and ADAMTS15) were identified as the key signaling pathways and candidate genes within the HPG axis responsible for different egg production performance between HEP and LEP. This is the first study comparing the transcriptomic profiles of all HPG axis-related tissues in HEP and LEP using RNA-seq in ducks to the best of our knowledge. These data are helpful to enrich our understanding of the classical HPG axis regulating the egg production performance and identify candidate genes that can be used for genetic selection in ducks.

Comparison of body size and reproductive hormones in high- and low-yielding Wulong geese

Wulong geese are renowned for their egg-laying and reproductive abilities. This work investigated the potential of using body size traits in the selection and breeding of high-yielding Wulong geese. A total of forty 479day-old female geese (high-yielding geese, n = 20; low-yielding geese, n = 20) were selected to evaluate the relationship between body weight, body size trait indicators, serum reproductive hormones, and biochemical indicators. The results showed that serum estradiol (E2), glucose (GLU), and triglyceride (TG) concentrations, together with pubic spacing and abdominal circumference were significantly higher in high-yielding geese (P < 0.01), whereas the opposite was true for neck circumference, neck length, and tibial circumference. In addition, the serum testosterone (T) concentration and body weight were higher in high-yielding geese (P < 0.05). Neck circumference and neck length were negatively correlated with E2 and TG (P < 0.01); while pubic spacing and abdominal circumference were positively correlated with E2, GLU, and TG (P < 0.01), the highest correlation coefficient was 0.777 between TG and pubic spacing; T was also strongly associated with neck circumference (P < 0.01). In conclusion, high-yielding Wulong geese can be selected through neck circumference, neck length, pubic spacing, and abdominal circumference.

Effects of dietary corticosterone on the central adenosine monophosphate-activated protein kinase (AMPK) signaling pathway in broiler chickens

Glucocorticoids (GCs) induce the activation of the central adenosine 5'-monophosphate-activated protein kinase (AMPK) signaling pathway in birds. In this study, we aimed to investigate the effects of corticosterone (CORT) supplemented in diet on the central AMPK signaling pathway in broilers. The average daily gain was reduced by CORT treatment, and the average daily feed intake remained unchanged. Plasma glucose, triglyceride, total cholesterol, and CORT contents were increased by CORT administration. In addition, CORT treatment decreased the relative weights of heart, spleen, and bursa and increased the relative weights of liver and abdominal fat. The glycogen contents in the liver and breast muscle were higher in the chicks treated with CORT. CORT treatment upregulated the gene expression of mammalian target of rapamycin, glucocorticoid receptor, AMPKα2, neuropeptide Y(NPY), liver kinase B1 (LKB1), AMPKα1, and fatty acid synthase in the hypothalamus. Moreover, CORT treatment increased the protein levels of acetyl-coenzyme A carboxylase (ACC) phosphorylation and total AMPK and phosphorylated AMPK in the hypothalamus. Hence, CORT administration in the diet activated the LKB1-AMPK-NPY/ACC signaling pathway in the hypothalamus of broiler.

Endocrine and genetic factors affecting egg laying performance in chickens: a review

1. Egg-laying performance reflects the overall reproductive performance of breeding hens. The genetic traits for egg-laying performance have low or medium heritability, and, depending on the period involved, usually ranges from 0.16 to 0.64. Egg-laying in chickens is regulated by a combination of environmental, endocrine and genetic factors. 2. The main endocrine factors that regulate egg-laying are gonadotropin-releasing hormone (GnRH), prolactin (PRL), follicle-stimulating hormone (FSH) and luteinising hormone (LH). 3. In the last three decades, many studies have explored this aspect at a molecular genetic level. Recent studies identified 31 reproductive hormone-based candidate genes that were significantly associated with egg-laying performance. With the development of genome-sequencing technology, 64 new candidate genes and 108 single nucleotide polymorphisms (SNPs) related to egg-laying performance have been found using genome-wide association studies (GWAS), providing novel insights into the molecular genetic mechanisms governing egg production. At the same time, microRNAs that regulate genes responsible for egg-laying in chickens were reviewed. 4. Research on endocrinological and genetic factors affecting egg-laying performance will greatly improve the reproductive performance of chickens and promote the protection, development, and utilisation of poultry. This review summarises studies on the endocrine and genetic factors of egg-laying performance in chickens from 1972 to 2019.

POMC gene expression, polymorphism, and the association with reproduction traits in chickens

Reproduction trait is one of the most important economic traits in poultry industry. This study was aimed to investigate the mRNA expression levels, single nucleotide polymorphisms (SNP) of POMC gene, and the association with reproduction traits in chickens. Five SNP (g.958 G > A, g.1374 G > C, g.1393 G > A, g.1817 C > T, and g.1918G > A) were detected in introns of POMC gene in 317 Zhenning yellow chickens. Association analysis revealed that g.958 G > A and g.1817 C > T showed significantly associations with fertilization rate, hatching rate of hatching eggs, and hatching rate of fertilized eggs in chickens. Simultaneously, g.1374 G > C and g.1918G > A were both associated with egg weight at 300 D of age (P < 0.05). The SNP of g.958 G > A, g.1393 G > A, and g.1817 C > T were all associated with E2 hormone levels (P < 0.05). The result of mRNA expression levels in different tissues showed that POMC mRNA expression level in the pituitary was higher than those in the other tissues and varied in different genotypes. In conclusion, the results in this study provided new evidences that polymorphisms of the POMC gene have potential effects on reproduction traits in chickens. The 5 SNP detected in this study could be potential markers for improving reproduction traits in chickens.

Polymorphisms of pro-opiomelanocortin gene and the association with reproduction traits in chickens

Pro-opiomelanocortin (POMC) is a member of prohormone family and has important functions in stress response, skin pigmentation, thermoregulation and reproduction. In this study, the single nucleotide polymorphisms (SNPs) of POMC gene exons were detected by direct sequencing in 317 Zhenning yellow chickens. The sequencing results indicated there were seven mutation sites (g.1140C > T, g.1185 T > C, g.2085 T > C, g.3566A > C, g.3572 G > A, g.3594 G > A and g.3628 G > A) and all of these were synonymous. Furthermore, seven haplotypes were formed and sixteen diplotypes were obtained. The associations between the POMC gene polymorphisms or diplotypes and reproduction traits were also analyzed. The association analysis results indicated that the SNP of g.1140C > T was associated with egg production at 300 d of age (E300), fertilization rate (FR), hatching rate of hatching eggs (HEHR) and hatching rate of fertilized eggs (FEHR; P < 0.05). The SNP of g.3566A>C was associated with FR (P < 0.05), SNP of g.3594G>A was associated with egg weight at 300d of age (EW300; P < 0.05), and SNP of g.3628G>A was associated with HEHR and FEHR (P < 0.01), respectively. Furthermore, chickens with H2H3 diplotype had greater EW300 and FR than those with H1H7 and H3H4 diplotypes (P < 0.05). These results indicate the expression of the POMC gene had significant genotype effects on the reproduction traits of Zhenning yellow chickens, and that the H2H3 diplotype could be used as a potential genetic marker to improve the reproduction traits in chicken breeding.

Fasting differentially alters the hypothalamic proteome of chickens from lines with the propensity to be anorexic or obese

BACKGROUND

The hypothalamus is the ultimate modulator of appetite and energy balance and therefore sensitive to changes in nutritional state. Chicks from lines selected for low (LWS) and high (HWS) body weight are hypophagic and compulsive eaters, respectively, and differ in their propensity to become obese and in their hypothalamic mRNA response to fasting.

METHODS

As fasting-induced changes in hypothalamic proteins are unknown, we investigated the hypothalamic proteomes of 5-day old LWS and HWS chicks in the fed and fasted states using a label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach.

RESULTS

A total of 744 proteins were identified in the chicken hypothalamus, and 268 differentially abundant proteins were identified among four pairwise comparisons. Ninety-five proteins were associated with the response to fasting in HWS chicks, and 23 proteins were associated with the response to fasting in LWS chicks. Fasting-responsive proteins in HWS chicks were significantly enriched in ATP metabolic processes, glyoxylate/dicarboxylate metabolism, and ribosome function. There was no enrichment for any pathways in LWS chicks in response to fasting. In the fasted and fed states, 159 and 119 proteins differed between HWS and LWS, respectively. Oxidative phosphorylation, citric acid cycle, and carbon metabolism were the main pathways associated with differences between the two lines of chicks. Enzymes associated with metabolic pathways differed between HWS and LWS in both nutritional states, including fumarase, aspartate aminotransferase, mitochondrial GOT2, 3-hydroxyisobutyrate dehydrogenase, chondrogenesis associated lipocalin, sialic acid synthase, arylamine N-acetyltransferase, pineal gland isozyme NAT-3, and succinate dehydrogenase [ubiquinone] flavoprotein subunit, mitochondrial.

CONCLUSIONS

These results provide insights into the hypothalamic metabolic pathways that are affected by nutritional status and the regulation of appetite and eating behavior.

Annotation of differential protein expression in the hypothalami of layer-type Taiwan country chickens in response to acute heat stress

The hypothalamus is the coordinating center for maintaining temperature homeostasis. In this study, global protein expression in the hypothalami of layer-type Taiwan country chickens in response to acute heat stress was investigated. Twelve 30-week-old female TCCs were divided into three acute heat-stressed groups, namely acute heat stress at 36 °C for 4 h with 0 h (without recovery, H4R0), 2 h (H4R2), or 6 h (H4R6) of recovery. A control group was maintained at 25 °C. Hypothalamus samples were collected at the end of each time point for proteomic analysis. The analysis results revealed that 134 protein spots representing 118 distinct proteins exhibited differential expressions after acute heat stress treatment. Results of gene ontology analysis showed that most of the differentially expressed proteins are involved in carbohydrate metabolism, cellular processes, actin cytoskeleton organization, and responses to stimuli. Functional pathway analysis results suggested that the proteins are associated with networks of carbon metabolism, glycolysis, and gluconeogenesis. Upregulation of the expression of triosephosphate isomerase, phosphoglycerate kinase, pyruvate kinase, alpha-enolase, glycogen phosphorylase (brain form), phosphoglucomutase, L-lactate dehydrogenase A chain and downregulation of 6-phosphogluconolactonase expression indicated an increase in the glycolytic activity and glucose supply for ATP production in the hypothalami in response to heat stress. By contrast, upregulated expressions of heat shock protein 90 alpha, glutathione S-transferase 2s, peroxiredoxin-1, and dihydropyrimidinase-like 2 suggested that acute heat stress adversely affects the hypothalamus; thus, it induces mechanisms that prevent oxidative damage and endoplasmic reticulum stress. In conclusion, acute heat stress induces differential protein expression in the hypothalami of the L2 strain Taiwan country chickens, which may manifest detrimental effects. Furthermore, differential expression is a critical response in the hypothalamus for the regulation of thermotolerance.

Proteomic analysis of the hypothalamus of broiler-type Taiwan country chickens in response to acute heat stress

The hypothalamus is a critical center for regulating heat retention or dissipation. This study investigated global protein changes in the hypothalamus of broiler-type Taiwan country chickens (TCCs) after acute heat stress. Twelve TCC hens aged 30 weeks were allocated to groups subjected to acute heat stress at 38°C for 2 hr without recovery, with 2 hr of recovery, and with 6 hr of recovery; a control group was maintained at 25°C. Hypothalami were collected for protein expression analysis at the end of each time point. The results showed 114 protein spots differentially expressed after acute heat stress. Most of the differentially expressed proteins were involved in cellular processes, metabolism, transport, and cellular component organization. Functional annotation analysis suggested that these proteins were related to cellular defensive responses against heat and oxidative stress, detoxification and toxin export/delivery, cytoskeleton integrity, oxygen transport, and neural development. The results of this study suggest that acute heat stress damages the hypothalamus of broiler-type TCCs through oxidative stress and provokes a series of responses to stabilize protein structures, degrade misfolded proteins, and remodel cytoskeletons for attenuating the detrimental effects by acute heat stress.

Comparative proteomic analysis of hypothalamus tissue from Huoyan geese between pre-laying period and laying period using an iTRAQ-based approach

The hypothalamus plays a central role in controlling poultry endocrine and reproductive activities. So far there is limited information focused on the proteome profiles of the hypothalamus from geese during different stages of the egg-laying cycle. In order to identify proteins regulating the egg-laying process of Huoyan geese, we investigated the proteome profiles of the hypothalamus from Huoyan geese during the laying period and pre-laying period by applying an isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomic technology. A total number of 3,337 were identified and quantified, of which 18 were significantly up-regulated and 16 were significantly down-regulated. These differentially expressed proteins were subjected to bioinformatics analyses based on the Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway. Some of these were revealed to be involved in hormone and neurotransmitter secretion, exocytosis, calcium ion transport and synaptic transmission. Subsequently, excitatory amino acid transporter 2, complexin-1 and inositol 1,4,5-trisphosphate receptor, type 3 were confirmed at the messenger RNA level using quantitative real-time RT-PCR. Then, the abundance change of these proteins was verified further using Western blotting analysis. These data may aid in elucidating the molecular mechanism of higher laying performance in Huoyan geese.

Functional genomics study of acute heat stress response in the small yellow follicles of layer-type chickens

This study investigated global gene and protein expression in the small yellow follicle (SYF; 6-8 mm in diameter) tissues of chickens in response to acute heat stress. Twelve 30-week-old layer-type hens were divided into four groups: control hens were maintained at 25 °C while treatment hens were subjected to acute heat stress at 36 °C for 4 h without recovery, with 2-h recovery, and with 6-h recovery. SYFs were collected at each time point for mRNA and protein analyses. A total of 176 genes and 93 distinct proteins with differential expressions were identified, mainly associated with the molecular functions of catalytic activity and binding. The upregulated expression of heat shock proteins and peroxiredoxin family after acute heat stress is suggestive of responsive machineries to protect cells from apoptosis and oxidative insults. In conclusion, both the transcripts and proteins associated with apoptosis, stress response, and antioxidative defense were upregulated in the SYFs of layer-type hens to alleviate the detrimental effects by acute heat stress. However, the genomic regulations of specific cell type in response to acute heat stress of SYFs require further investigation.

Proteomic Analysis of Thermal Regulation of Small Yellow Follicles in Broiler-Type Taiwan Country Chickens

Heat stress hampers egg production and lowers fertility in layers. This study investigated global protein abundance in the small yellow follicles (SYFs, 6–8 mm diameter) of a broiler-type strain of Taiwan country chickens (TCCs) under acute heat stress. Twelve 30-week-old TCC hens were allocated to a control group maintained at 25°C, and to three acute heat-stressed groups subjected to 38°C for 2 h without recovery, with 2-h recovery, or with 6-h recovery. Two-dimensional difference gel electrophoresis analysis identified 119 significantly differentially expressed proteins after acute heat exposure. Gene ontology analysis revealed that most of these proteins are involved in molecular binding (34%), catalytic activity (23%), and structural molecule activity (11%), and participate in metabolic processes (20%), cellular processes (20%), and cellular component organization or biogenesis (11%). Proteins associated with stress response and survival (HSP25, HSP47, HSP70, HSC70, HSPA9), cytoskeleton remodeling, mitochondrial metabolic process of ATP production, antioxidative defense (peroxiredoxin-6), cargo lipid export and delivery (vitellogenin, apolipoprotein B and A1), and toxin/metabolite clearance and delivery (albumin) were upregulated after acute heat stress in the SYFs of TCCs. No overt cell death and atresia were observed in SYFs after acute heat stress. Collectively, these responses may represent a protective mechanism to maintain follicle cell integrity and survival, thereby ensuring a sufficient pool of SYFs for selection into the ovulation hierarchy for successful egg production.

Comparative proteomic analysis of pituitary glands from Huoyan geese between pre-laying and laying periods using an iTRAQ-based approach

In this study, we performed a comprehensive evaluation of the proteomic profile of the pituitary gland of the Huoyan goose during the laying period compared to the pre-laying period using an iTRAQ-based approach. Protein samples were prepared from pituitary gland tissues of nine pre-laying period and nine laying period geese. Then the protein samples from three randomly selected geese within each period were pooled in equal amounts to generate one biological sample pool. We identified 684 differentially expressed proteins, including 418 up-regulated and 266 down-regulated proteins. GO annotation and KEGG pathway analyses of these proteins were conducted. Some of these proteins were found to be associated with hormone and neurotransmitter secretion and transport, neuropeptide signalling and GnRH signalling pathways, among others. Subsequently, the modification of the abundance of three proteins (prolactin, chromogranin-A and ITPR3) was verified using western blotting. Our results will provide a new source for mining genes and gene products related to the egg-laying performance of Huoyan geese, and may provide important information for the conservation and utilization of local goose breeds.

High-throughput sequencing of pituitary and hypothalamic microRNA transcriptome associated with high rate of egg production

Background

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.

Results

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.

Conclusions

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3644-3) contains supplementary material, which is available to authorized users.

Seasonal and photoperiodic regulation of reproductive hormones and related genes in Yangzhou geese

This study aimed at the reproductive endocrine profile under a natural photoperiod in Yangzhou female geese. Geese in the breeding industry were exposed to a natural photoperiod and the results showed the breeding season of Yangzhou geese initiated in autumn, reached peak in February and March, and terminated in June. Fifteen female geese were randomly selected for blood collection samples monthly. The results showed serum luteinizing hormone (LH) concentrations in female geese were higher in the breeding season than in the non-breeding season. The concentrations of Prolactin (PRL) were also high in the breeding season. Follicle-stimulating hormone (FSH) concentrations were high from March to May and decreased to low levels in other periods. Furthermore, 6 female birds were selected randomly monthly, sacrificed, and the hypothalamus and pituitary isolated. The expressions of FSH were also high in the breeding season, while the expressions of the gonadotropin-releasing hormone (GnRH) fluctuated. These results indicated that the reproductive hormones and their transcript expressions were closely related to the reproductive activities in Yangzhou geese.

Annotation of Differential Gene Expression in Small Yellow Follicles of a Broiler-Type Strain of Taiwan Country Chickens in Response to Acute Heat Stress

This study investigated global gene expression in the small yellow follicles (6-8 mm diameter) of broiler-type B strain Taiwan country chickens (TCCs) in response to acute heat stress. Twelve 30-wk-old TCC hens were divided into four groups: control hens maintained at 25°C and hens subjected to 38°C acute heat stress for 2 h without recovery (H2R0), with 2-h recovery (H2R2), and with 6-h recovery (H2R6). Small yellow follicles were collected for RNA isolation and microarray analysis at the end of each time point. Results showed that 69, 51, and 76 genes were upregulated and 58, 15, 56 genes were downregulated after heat treatment of H2R0, H2R2, and H2R6, respectively, using a cutoff value of two-fold or higher. Gene ontology analysis revealed that these differentially expressed genes are associated with the biological processes of cell communication, developmental process, protein metabolic process, immune system process, and response to stimuli. Upregulation of heat shock protein 25, interleukin 6, metallopeptidase 1, and metalloproteinase 13, and downregulation of type II alpha 1 collagen, discoidin domain receptor tyrosine kinase 2, and Kruppel-like factor 2 suggested that acute heat stress induces proteolytic disintegration of the structural matrix and inflamed damage and adaptive responses of gene expression in the follicle cells. These suggestions were validated through gene expression, using quantitative real-time polymerase chain reaction. Functional annotation clarified that interleukin 6-related pathways play a critical role in regulating acute heat stress responses in the small yellow follicles of TCC hens.

Profiling of differential gene expression in the hypothalamus of broiler-type Taiwan country chickens in response to acute heat stress

Acute heat stress severely impacts poultry production. The hypothalamus acts as a crucial center to regulate body temperature, detect temperature changes, and modulate the autonomic nervous system and endocrine loop for heat retention and dissipation. The purpose of this study was to investigate global gene expression in the hypothalamus of broiler-type B strain Taiwan country chickens after acute heat stress. Twelve 30-week-old hens were allocated to four groups. Three heat-stressed groups were subjected to acute heat stress at 38 °C for 2 hours without recovery (H2R0), with 2 hours of recovery (H2R2), and with 6 hours of recovery (H2R6). The control hens were maintained at 25 °C. At the end, hypothalamus samples were collected for gene expression analysis. The results showed that 24, 11, and 25 genes were upregulated and 41, 15, and 42 genes were downregulated in H2R0, H2R2, and H2R6 treatments, respectively. The expressions of gonadotropin-releasing hormone 1 (GNRH1), heat shock 27-kDa protein 1 (HSPB1), neuropeptide Y (NPY), and heat shock protein 25 (HSP25) were upregulated at all recovery times after heat exposure. Conversely, the expression of TPH2 was downregulated at all recovery times. A gene ontology analysis showed that most of the differentially expressed genes were involved in biological processes including cellular processes, metabolic processes, localization, multicellular organismal processes, developmental processes, and biological regulation. A functional annotation analysis showed that the differentially expressed genes were related to the gene networks of responses to stress and reproductive functions. These differentially expressed genes might be essential and unique key factors in the heat stress response of the hypothalamus in chickens.

Feed restriction ameliorates metabolic dysregulation and improves reproductive performance of meat-type country chickens

Restricted feed intake improves egg production in Cornish×Plymouth Rock (broiler) hens. Red-feather (RF) and Black-feather (BF) chickens are 2 local strains of non-broiler meat-type chickens whose egg production has declined with continued selection for meat yield, and which are unstudied regarding restricted feeding and egg-laying improvement. Sixteen week old RF and BF pullets were either fed ad libitum (AL) or restricted to 85% AL intake (R). At 35wk and 50wk R-hens showed improved egg production and less abnormal ovarian morphology than AL-hens. Obesity, hepatic steatosis, lipotoxic change to plasma lipids, and systemic inflammation induced by AL feeding in RF and BF hens were similar to those observed previously in AL-broiler hens. Egg production was negatively correlated to body weight, fractional abdominal fat weight and plasma NEFA concentrations in AL hens (P<0.05). AL-hen hierarchical follicles accumulated ceramide and increased interleukin-1β production (P<0.05) in conjunction with increased granulosa cell apoptosis, follicle atresia, ovarian regression, and reduced plasma 17β-estradiol concentrations (P<0.05). The present outcomes from non-broiler but nevertheless meat-type country chicken strains indicate that selection for rapid growth and increased meat yield fundamentally changes energy metabolism in a way that renders hens highly susceptible to reproductive impairment from lipid dysregulation and pro-inflammatory signaling rather than impaired resource allocation per se.

Gene expression profiling in the pituitary gland of laying period and ceased period huoyan geese

Huoyan goose is a Chinese local breed famous for its higher laying performance, but the problems of variety degeneration have emerged recently, especially a decrease in the number of eggs laid. In order to better understand the molecular mechanism that underlies egg laying in Huoyan geese, gene profiles in the pituitary gland of Huoyan geese taken during the laying period and ceased period were investigated using the suppression subtractive hybridization (SSH) method. Total RNA was extracted from pituitary glands of ceased period and laying period geese. The cDNA in the pituitary glands of ceased geese was subtracted from the cDNA in the pituitary glands of laying geese (forward subtraction); the reverse subtraction was also performed. After sequencing and annotation, a total of 30 and 24 up and down-regulated genes were obtained from the forward and reverse SSH libraries, respectively. These genes mostly related to biosynthetic process, cellular nitrogen compound metabolic process, transport, cell differentiation, cellular protein modification process, signal transduction, small molecule metabolic process. Furthermore, eleven genes were selected for further analyses by quantitative real-time PCR (qRT-PCR). The qRT-PCR results for the most part were consistent with the SSH results. Among these genes, Synaptotagmin-1 (SYT1) and Stathmin-2 (STMN2) were substantially over-expressed in laying period compared to ceased period. These results could serve as an important reference for elucidating the molecular mechanism of higher laying performance in Huoyan geese.

Proteomic analysis of visceral adipose tissue in pre-obese patients with type 2 diabetes

The mechanisms involved in the progression to overt diabetes in pre-obese subjects remain unclear. Therefore, a nontargeted evaluation of differences in the protein abundance of visceral adipose tissue (VAT) obtained from pre-obese diabetic subjects and pre-obese subjects showing normal glucose tolerance may provide novel insights on the molecular processes involved in the progression to overt diabetes in pre-obesity. Diabetic patients showed increased VAT abundance of glutathione S-transferase Mu 2, peroxiredoxin-2, antithrombin-III, apolipoprotein A-IV, Ig κ chain C region, mitochondrial aldehyde dehydrogenase and actin, and decreased abundance of annexin-A1, retinaldehyde dehydrogenase-1, and vinculin, compared with their non-diabetic counterparts. These proteins are involved in cytoskeleton function and structure, oxidative stress, inflammation and retinoid metabolism. The presence of diabetes influences the VAT abundance of several proteins. Hence, the proteins identified here could be considered candidate molecules in future studies addressing the role that VAT dysfunction plays in the development of type 2 diabetes.

A proteomic approach to identify seminal plasma proteins in roosters (Gallus gallus domesticus)

Considering the interest in avian semen processing and storage, the objective of this study was to identify the domestic fowl seminal plasma proteins using two-dimensional gel electrophoresis (2-DE) and mass spectrometry MS/MS. For three times in a 4-month period, seminal plasma was obtained from semen collected from four local male chickens (Gallus gallus domesticus) and prepared for two-dimensional polyacrylamide gel electrophoresis. A total of 83 spots were detected across all gels and analyzed by MALDI-TOF/TOF. Among these spots, 17 have been successfully identified. The most intensely stained spots were recognized as serum albumin, ovotransferrin, alpha-enolase, fatty acid binding protein, thioredoxin, trypsin inhibitor CITI-1 and gallinacin-9. From these proteins, two are characteristic of avian seminal plasma, the ovotransferrin and gallinacin-9, and one is specific of the Gallus species, the chicken trypsin inhibitor CITI-1.

PreZon: prediction by zone and its application to egg productivity in chickens

Taiwan red-feathered country chickens (TRFCCs) are one of the main meat resources in Taiwan. Due to the lack of any systematic breeding programs to improve egg productivity, the egg production rate of this breed has gradually decreased. The prediction by zone (PreZone) program was developed to select the chickens with low egg productivity so as to improve the egg productivity of TRFCCs before they reach maturity. Three groups (A, B, and C) of chickens were used in this study. Two approaches were used to identify chickens with low egg productivity. The first approach used predictions based on a single dataset, and the second approach used predictions based on the union of two datasets. The levels of four serum proteins, including apolipoprotein A-I, vitellogenin, X protein (an IGF-I-like protein), and apo VLDL-II, were measured in chickens that were 8, 14, 22, or 24 weeks old. Total egg numbers were recorded for each individual bird during the egg production period. PreZone analysis was performed using the four serum protein levels as selection parameters, and the results were compared to those obtained using a first-order multiple linear regression method with the same parameters. The PreZone program provides another prediction method that can be used to validate datasets with a low correlation between response and predictors. It can be used to find low and improve egg productivity in TRFCCs by selecting the best chickens before they reach maturity.

The GTPase activating Rap/RanGAP domain-like 1 gene is associated with chicken reproductive traits

Background

Abundant evidence indicates that chicken reproduction is strictly regulated by the hypothalamic-pituitary-gonad (HPG) axis, and the genes included in the HPG axis have been studied extensively. However, the question remains as to whether any other genes outside of the HPG system are involved in regulating chicken reproduction. The present study was aimed to identify, on a genome-wide level, novel genes associated with chicken reproductive traits.

Methodology/Principal Finding

Suppressive subtractive hybridization (SSH), genome-wide association study (GWAS), and gene-centric GWAS were used to identify novel genes underlying chicken reproduction. Single marker-trait association analysis with a large population and allelic frequency spectrum analysis were used to confirm the effects of candidate genes. Using two full-sib Ningdu Sanhuang (NDH) chickens, GARNL1 was identified as a candidate gene involved in chicken broodiness by SSH analysis. Its expression levels in the hypothalamus and pituitary were significantly higher in brooding chickens than in non-brooding chickens. GWAS analysis with a NDH two tail sample showed that 2802 SNPs were significantly associated with egg number at 300 d of age (EN300). Among the 2802 SNPs, 2 SNPs composed a block overlapping the GARNL1 gene. The gene-centric GWAS analysis with another two tail sample of NDH showed that GARNL1 was strongly associated with EN300 and age at first egg (AFE). Single marker-trait association analysis in 1301 female NDH chickens confirmed that variation in this gene was related to EN300 and AFE. The allelic frequency spectrum of the SNP rs15700989 among 5 different populations supported the above associations. Western blotting, RT-PCR, and qPCR were used to analyze alternative splicing of the GARNL1 gene. RT-PCR detected 5 transcripts and revealed that the transcript, which has a 141 bp insertion, was expressed in a tissue-specific manner.

Conclusions/Significance

Our findings demonstrate that the GARNL1 gene contributes to chicken reproductive traits.

Polymorphisms associated with egg number at 300 days of age in chickens

We looked for variations that could be associated with chicken egg number at 300 days of age (EN300) in seven genes of the hypothalamic-pituitary-gonadal axis, including gonadotrophin-releasing hormone-I (GnRH-I), GnRH receptor (GnRHR), neuropeptide Y (NPY), dopamine D2 receptor (DRD2), vasoactive intestinal polypeptide (VIP), VIP receptor-1 (VIPR-1), prolactin (PRL), and the QTL region between 87 and 105 cM of the Z chromosome. Ten mutations in the seven genes were chosen to do marker-trait association analyses in a population comprising 1310 chickens, which were obtained from a company located in Guangdong Province of China. The C1704887T of VIPR-1 was found to have a highly significant association with EN300. The T5841629C of DRD2 and the C1715301T of VIPR-1 were significantly associated with EN300. A highly significant association was also found between the C1704887T-C1715301T haplotypes of VIPR-1 and EN300. H1H3 had the highest EN300. Four PCR-RFLP variations in the candidate QTL region were selected to investigate their genetic effects on EN300. The haplotypes of T32742468C-G32742603A in this region showed a highly significant association with EN300. Bioinformatics analyses showed that both T32742468C and G32742603A were located in intron 1 of the SH3-domain GRB2-like 2 (SH3GL2) gene. We conclude that five SNPs, including C1704887T and C1715301T of VIPR-1, T5841629C of DRD2, and T32742468C and G32742603A of SH3GL2, would be useful as markers for breeding to increase chicken EN300.

Proteome changes in Thai indigenous chicken muscle during growth period

Proteomic profiling of the pectoralis muscle of Thai indigenous chickens during growth period was analyzed using two-dimensional gel electrophoresis (2-DE) and matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF/MS). A total of 259, 161, 120 and 107 protein spots were found to be expressed in the chicken pectoralis muscles at 0, 3, 6 and 18 weeks of age, respectively. From these expressed proteins, five distinct protein spots were significantly associated with chicken age. These protein spots were characterized and showed homology with phosphoglycerate mutase 1 (PGAM1), apolipoprotein A1 (APOA1), triosephosphate isomerase 1 (TPI1), heat shock protein 25 kDa (HSP25) and fatty acid binding protein 3 (FABP3). These five protein spots were categorized as follows: (i) the expression levels of PGAM1 and TPI1 proteins were positively correlated with chicken aging (p<0.05), (ii) the expression levels of APOA1 and FABP3 proteins were negatively correlated with chicken aging (p<0.05) and (iii) the expression levels of the HSP25 protein were up- and down-regulated during growth period. Moreover, the mRNA expression levels of the FABP3 and HSP25 genes were significantly decreased in muscle during the growth period (p<0.05), whereas no significant changes of the PGAM1, TPI1 and APOA1 gene expression from the chicken muscle was observed. The identified proteins were classified as metabolic and stress proteins. This demonstrates a difference in energy metabolism and stress proteins between age groups and shows that proteomics is a useful tool to uncover the molecular basis of physiological differences in muscle during the growth period.

Optimized sample preparation for two-dimensional gel electrophoresis of soluble proteins from chicken bursa of Fabricius

BACKGROUND

Two-dimensional gel electrophoresis (2-DE) is a powerful method to study protein expression and function in living organisms and diseases. This technique, however, has not been applied to avian bursa of Fabricius (BF), a central immune organ. Here, optimized 2-DE sample preparation methodologies were constructed for the chicken BF tissue. Using the optimized protocol, we performed further 2-DE analysis on a soluble protein extract from the BF of chickens infected with virulent avibirnavirus. To demonstrate the quality of the extracted proteins, several differentially expressed protein spots selected were cut from 2-DE gels and identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS).

RESULTS

An extraction buffer containing 7 M urea, 2 M thiourea, 2% (w/v) 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS), 50 mM dithiothreitol (DTT), 0.2% Bio-Lyte 3/10, 1 mM phenylmethylsulfonyl fluoride (PMSF), 20 U/ml Deoxyribonuclease I (DNase I), and 0.25 mg/ml Ribonuclease A (RNase A), combined with sonication and vortex, yielded the best 2-DE data. Relative to non-frozen immobilized pH gradient (IPG) strips, frozen IPG strips did not result in significant changes in the 2-DE patterns after isoelectric focusing (IEF). When the optimized protocol was used to analyze the spleen and thymus, as well as avibirnavirus-infected bursa, high quality 2-DE protein expression profiles were obtained. 2-DE maps of BF of chickens infected with virulent avibirnavirus were visibly different and many differentially expressed proteins were found.

CONCLUSION

These results showed that method C, in concert extraction buffer IV, was the most favorable for preparing samples for IEF and subsequent protein separation and yielded the best quality 2-DE patterns. The optimized protocol is a useful sample preparation method for comparative proteomics analysis of chicken BF tissues.

Functional genomics of the chicken--a model organism

Since the sequencing of the genome and the development of high-throughput tools for the exploration of functional elements of the genome, the chicken has reached model organism status. Functional genomics focuses on understanding the function and regulation of genes and gene products on a global or genome-wide scale. Systems biology attempts to integrate functional information derived from multiple high-content data sets into a holistic view of all biological processes within a cell or organism. Generation of a large collection ( approximately 600K) of chicken expressed sequence tags, representing most tissues and developmental stages, has enabled the construction of high-density microarrays for transcriptional profiling. Comprehensive analysis of this large expressed sequence tag collection and a set of approximately 20K full-length cDNA sequences indicate that the transcriptome of the chicken represents approximately 20,000 genes. Furthermore, comparative analyses of these sequences have facilitated functional annotation of the genome and the creation of several bioinformatic resources for the chicken. Recently, about 20 papers have been published on transcriptional profiling with DNA microarrays in chicken tissues under various conditions. Proteomics is another powerful high-throughput tool currently used for examining the dynamics of protein expression in chicken tissues and fluids. Computational analyses of the chicken genome are providing new insight into the evolution of gene families in birds and other organisms. Abundant functional genomic resources now support large-scale analyses in the chicken and will facilitate identification of transcriptional mechanisms, gene networks, and metabolic or regulatory pathways that will ultimately determine the phenotype of the bird. New technologies such as marker-assisted selection, transgenics, and RNA interference offer the opportunity to modify the phenotype of the chicken to fit defined production goals. This review focuses on functional genomics in the chicken and provides a road map for large-scale exploration of the chicken genome.

Laying traits and underlying transcripts, expressed in the hypothalamus and pituitary gland, that were associated with egg production variability in chickens

The objective was to characterize the potential laying traits and underlying transcripts expressed in the hypothalamus and pituitary gland that were associated with egg production variability in five genetic stocks of chickens: two commercial lines, Red- (n=12) and Black-feather (n=14) Taiwan country chickens (TCCs); two selected lines of TCCs, B (high body weight/comb size; n=17) and L2 (high-egg production; n=14); and a commercial single comb White Leghorn (WL; n=17). Six laying traits, age at first egg, clutch length, pause length, oviposition lag within clutch, follicle rapid growth period, and rate of yolk accumulation were measured. The significance of differential values among five chicken stocks and correlation coefficients between laying traits and number of eggs to 50 weeks of age or laying rate after first egg, and the expression level of 33 transcripts were determined. Longer clutch length and shorter oviposition lag within clutch contributed to a higher number of eggs to 50 weeks of age or laying rate after first egg in L2 (P<0.05) and WL strains (P<0.05). However, their rate of yolk accumulation (P<0.05) and follicle rapid growth period (P<0.05) were different, indicating the accumulation of different alleles after long-term, independent selection. Across all five strains, numbers of eggs to 50 weeks of age were positive correlated with average clutch length (P<0.05) as well as the rate of yolk accumulation (P<0.05). Expressions of PLAG1, STMN2, PGDS, PARK7, ANP32A, PCDHA@, SCG2, BDH and SAR1A transcripts contributed to number of eggs to 50 weeks of age (P<0.05) or laying rate after first egg (P<0.05). Analysis of correlation coefficients indicated that PLAG1 additionally played roles in decreasing average pause length. Two transcripts, PRL and GARNL1, specifically contributed to number of eggs to 50 weeks of age or laying rate after first egg by reducing oviposition lag within clutch (P<0.05) and/or increasing average clutch length (P<0.05), respectively. Expression level of NCAM1, contributed to laying rate after first egg by association with a shorter oviposition lag within clutch (P<0.05). The current study attributed egg production phenotype in five strains into several laying traits; correlations between these traits and expression levels of underlying transcripts expressed in the hypothalamus and pituitary gland were also established.

Differentially expressed transcripts in shell glands from low and high egg production strains of chickens using cDNA microarrays

We have constructed a tissue-specific in-house cDNA microarray to identify differentially expressed transcripts in shell glands from low (B) and high (L2) egg production strains of Taiwanese country chickens during their egg-laying period. The shell gland cDNA library was constructed from the high egg production strain. cDNA clones (7680) were randomly selected and their 5'-end sequences characterized. After excluding overlapping sequences, an in-house cDNA microarray, representing 2743 non-redundant transcripts, was generated for functional genomic studies. Using our microarray, we have successfully identified 85 differentially expressed transcripts from the two different strains of chicken shell glands. In this study, 34 of these transcripts were associated with signal transduction, protein biosynthesis, cell adhesion, cellular metabolism, skeletal development, cell organization and biogenesis. We selected a number of the differentially expressed transcripts for further validation using semi-quantitative RT-PCR. These included elongation factor 2 (EEF2), ovocalyxin-32 (OCX-32) and annexin A2 (ANXA2) which were expressed at high levels in the chicken shell glands of the B strain and, in contrast, the coactosin-like protein (COTL1), transcription factor SOX18 and MX protein were more highly expressed in the L2 strain. Our results suggest that these differentially expressed transcripts may be suitable to use as molecular markers for high rates of egg production, and now need to be investigated further to assess whether they can be applied for use in breeding selection programs in Taiwanese country chickens.

Avian proteomics: advances, challenges and new technologies

Proteomics is defined as an analysis of the full complement of proteins of a cell or tissue under given conditions. Avian proteomics, or more specifically chicken proteomics, has focussed on the study of individual tissues and organs of interest to specific researchers. Researchers have looked at skeletal muscle and growth, and embryonic development and have performed initial studies in avian disease. Traditional proteomics involves identifying and cataloguing proteins in a cell and identifying relative changes in populations between two or more states, be that physiological or disease-induced states. Recent advances in proteomic technologies have included absolute quantification, proteome simplification and the ability to determine the turnover of individual proteins in a global context. This review discusses the current developments in this relatively new field, new technologies and how they may be applied to biological questions, and the challenges faced by researchers in this ever-expanding and exciting field.

Using Proteomics to Understand Avian Systems Biology and Infectious Disease

The proteome is defined as the protein complement to the genome. Proteomics is the study of the proteome. Several techniques are frequently used in proteomics; these include 2-hybrid systems, 2-dimensional gel electrophoresis, and mass spectrometry. Systems biology is a scientific approach that takes into account the complex relationships among and between genes and proteins and determines how all of these interactions come together to form a functional organism. Proteomic tools can simultaneously probe the properties of numerous proteins and thus are a great aid to the emerging field of systems biology, in which the functional interactions of numerous proteins are studied instead of studying individual proteins as isolated entities. In the field of avian biology, proteomics has been used to study everything from the development and function of organs and systems to the interactions of infectious agents and the altered states that they induce in their hosts.

Identification of transcripts related to high egg production in the chicken hypothalamus and pituitary gland

To identify transcripts related to high egg production expressed specifically in the hypothalamus and pituitary gland of the chicken, two subtracted cDNA libraries were constructed. Two divergently selected strains of Taiwan Country Chickens (TCCs), B (sire line) and L2 (dam line) were used; they had originated from a single population and were further subjected (since 1982) to selection for egg production to 40 wk of age and body weight/comb size, respectively. A total of 324 and 370 clones were identified from the L2-B (L2-subtract-B) and the B-L2 subtracted cDNA libraries, respectively. After sequencing and annotation, 175 and 136 transcripts that represented 53 known and 65 unknown non-redundant sequences were characterized in the L2-B subtracted cDNA library. Quantitative reverse-transcription (RT)-PCR was used to screen the mRNA expression levels of 32 randomly selected transcripts in another 78 laying hens from five different strains. These strains included the two original strains (B and L2) used to construct the subtracted cDNA libraries and an additional three commercial strains, i.e., Black- and Red-feather TCCs and Single-Comb White Leghorn (WL) layer. The mRNA expression levels of 16 transcripts were significantly higher in the L2 than in the B strain, whereas the mRNA expression levels of nine transcripts, BDH, NCAM1, PCDHA@, PGDS, PLAG1, PRL, SAR1A, SCG2 and STMN2, were significantly higher in two high egg production strains, L2 and Single-Comb WL; this indicated their usefulness as molecular markers of high egg production.

Expression of 25 high egg production related transcripts that identified from hypothalamus and pituitary gland in red-feather Taiwan country chickens

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.