Genetic effect of an A/G polymorphism in the HSP70 gene on thermotolerance in chicken.

Studying thermotolerance is important for the prevention of thermostress in chickens. This study aimed to analyze the effect of mutations in the heat shock protein 70 (HSP70) gene on chicken thermotolerance. The C.-69A>G SNP in the 5'-flanking region of the HSP70 gene was genotyped in Lingshan and White Recessive Rock (WRR) chickens. Association of this SNP with thermotolerance traits revealed it to be significantly associated with CD4+/CD8+, and potentially associated with heterophil-to-lymphocyte ratio in WRR chickens exposed to thermoneutral temperature (15°C). Online prediction detected a putative myeloid zinc finger protein 1 binding factor in the C.-69A>G mutation. Under acute thermostress, mRNA levels of HSP70 in individuals with different C.-69A>G genotypes varied in the heart, leg muscle, and liver tissues. The HSP70 protein was expressed at higher levels in individuals with the GG genotype than in those with the AA genotype. In heart and liver, protein expression of HSP70 in individuals with the GG genotype was significantly higher than in those with the AA genotype. In leg muscle, protein expression was higher in birds with the GG genotype than in those with the AA and AG genotypes. Luciferase activity of the GG genotype was significantly higher than that of the AA genotype, suggesting that the C.-69A>G SNP regulates HSP70 gene expression. These results indicate that the C.-69A>G SNP in the 5'-flanking region of the HSP70 gene might affect chicken thermotolerance and that the GG genotype might be advantageous for the prevention of thermostress.

Characterization of HSP70 and its expression in tissue: correlation with physiological and immune indices in goose (Anser cygnoides) serum.

We cloned the goose heat shock protein 70 gene (HSP70), to determine its sequence variation and elucidate its mRNA expression. We designed primers to amplify the entire goose HSP70 sequence. We used 10 commercial Wuzong goslings in a heat-stress experiment. We collected tissue samples for RNA extraction and quantitative real-time polymerase chain reaction (qRT-PCR). We analyzed the variation in expression of goose HSP70 before and after heat stress. We constructed a DNA pool from six different species, for single nucleotide polymorphism (SNP) screening. We detected 18 SNPs and selected three of these SNPs for correlation analysis with biological and immune traits in 200 Wuzong geese. We showed that T+237C was significantly correlated with the serum corticosterone level, whereas T+1122C was significantly correlated with the heterophil to lymphocyte ratio. Goose HSP70 contained no introns. The results of qRT-PCR analysis revealed significant gender differences in the expression of goose HSP70 at 40°C but not at 25°C; moreover, in general, expression was significantly higher at 40°C than at 25°C. With the exception of the leg muscle and cerebellum, HSP70 expression was significantly higher in male geese than in female geese. Our results indicate that goose HSP70 plays an important role in response to severe heat stress.

Association analysis between SNPs in the 5'-flanking region of the chicken GRP78 gene, thermotolerance parameters, and tissue mRNA expression.

Glucose-regulated protein 78 (GRP78) is a molecular chaperone in the endoplasmic reticulum and can be induced by different kinds of environmental and physiological stress. Thus far, the role of the GRP78 gene in thermotolerance in chickens has not been investigated. In the present study, we detected sequence variations in the 5ꞌ-flanking region of the GRP78 gene and evaluated several thermotolerance parameters, such as T3, corticosterone, H/L ratio, and levels of CD3(+), CD4(+), and CD8(+) T cells, to further determine its associations at 35° and 15°C. The sequencing results revealed 10 SNPs in the 5'-flanking region of the GRP78 gene, and seven mutations were chosen for further genotyping in a White Recessive Rock (WRR) chicken population. The SNP C.-744C>G in WRR chickens was significantly correlated with heat tolerance parameters under both conditions; it may therefore exert a potential hereditary effect on heat tolerance, and the genotype GG may be advantageous for thermotolerance. The heart, liver, brain, and leg muscle tissues of 8-day-old WRR chickens were sampled from heat stress groups, which were defined by exposure to 1, 2, 3, and 6 h of persistent thermal stress, and a control group, which was not exposed to thermal stress. Quantitative real-time polymerase chain reaction assay indicated that the mRNA expression level of the GRP78 gene increased gradually under heat stress, peaked at 3 h, and then decreased. We conclude that the mRNA expression of the GRP78 gene is time- and tissue-dependent.

Analysis of genetic diversity of the heat shock protein 70 gene on the basis of abundant sequence polymorphisms in chicken breeds.

This study was designed to detect the sequence variation of the chicken heat shock protein 70 (HSP70) gene. A total of 102 individuals from 8 native Chinese breeds together with Dwarf White Chicken and Red Junglefowl were used to detect sequence variations. The coding regions of the chicken HSP70 gene from 102 individuals were cloned and sequenced. Thirty-six variations were identified, which included 34 single nucleotide polymorphisms and 2 indel mutations. Fifty-seven haplotypes were observed, of which, 43 were breed-specific and 14 were shared. There were 7 Red Junglefowl-specific haplotypes, while Haidong and Silkie only had 2 specific haplotypes. Eleven and 3 haplotypes were shared between and within species, respectively. The variation in nucleotide diversity (Pi) and average number of nucleotide differences (K) among species were consistent. The total Pi of HSP70 was 0.0016, and the total K was 4.1998. The Pi value of Red Junglefowl was the highest (0.0018) and K was 4.8000, while the Pi of Silkie was the lowest (0.0010) and K was 2.5000. These results demonstrated that variation in chicken HSP70 was abundant between and within species.

Alteration of HSF3 and HSP70 mRNA expression in the tissues of two chicken breeds during acute heat stress.

This study aimed to estimate changes in HSF3 and HSP70 mRNA expression in stress-sensitive tissues of 2 chicken breeds during acute heat stress. Lingshan chickens (LSC) and White Recessive Rock (WRR) (24 chickens of each breed) were randomly divided into 4 groups (0, 2, 3, and 6 h of heat treatment). With increasing heat treatment time, both HSF3 and HSP70 expression first declined and then showed a significant increase in both breeds. However, HSP70 expression decreased in the heart following 6 h of heat treatment, whereas HSF3 expression continued to increase. After 2 h of heat treatment, HSF3 expression was significantly higher in the brain and leg muscle of LSC compared to WRR (P < 0.05, P < 0.01). In comparison, HSP70 expression was significantly higher in the liver and leg muscle of WRR compared to LSC (P < 0.01, P < 0.05). After 3 h of heat treatment, HSF3 expression was significantly higher in the brain and leg muscle of LSC compared to WRR (P < 0.01). In comparison, HSP70 expression was significantly higher in the liver and heart of LSC compared to WRR (P < 0.01). These results indicate that the expression of HSF3 and HSP70 mRNA in LSC and WRR exhibit species-specific and tissue-specific differences during heat treatment.

Exploring the molecular mechanism of acute heat stress exposure in broiler chickens using gene expression profiling.

The process of heat regulation is complex and its exact molecular mechanism is not fully understood. In this study, to investigate the global gene regulation response to acute heat exposure, gene microarrays were exploited to analyze the effects of heat stress on three tissues (brain, liver, leg muscle) of the yellow broiler chicken (Gallus gallus). We detected 166 differentially expressed genes (DEGs) in the brain, 219 in the leg muscle and 317 in the liver. Six of these genes were differentially expressed in all three tissues and were validated by qRT-PCR, and included heat shock protein genes (HSPH1, HSP25), apoptosis-related genes (RB1CC1, BAG3), a cell proliferation and differentiation-related gene (ID1) and the hunger and energy metabolism related gene (PDK). All these genes might be important factors in chickens suffering from heat stress. We constructed gene co-expression networks using the DEGs of the brain, leg muscle and liver and two, four and two gene co-expression modules were identified in these tissues, respectively. Functional enrichment of these gene modules revealed that various functional clusters were related to the effects of heat stress, including those for cytoskeleton, extracellular space, ion binding and energy metabolism. We concluded that these genes and functional clusters might be important factors in chickens under acute heat stress. Further in-depth research on the newly discovered heat-related genes and functional clusters is required to fully understand their molecular functions in thermoregulation.

Promoter methylation negatively correlated with mRNA expression but not tissue differential expression after heat stress.

DNA methylation plays a central role in gene expression. In this study, we detected the promoter methylation pattern of the chicken heat shock protein 70 (HSP70) gene and its association with messenger RNA (mRNA) expression before and after heat shock. The results showed that mRNA expression increased in response to heat stress and peaked at 3 h before dropping. Hypomethylation of the HSP70 promoter occurred in all of the groups studied, but the difference between groups within tissue type was not significant. The DNA methylation level of the control and the 6-h treatment groups was slightly higher than that of the 3-h treatment group in brain tissue and leg muscle. Correlation analysis between mRNA expression and DNA methylation of HSP70 showed that DNA methylation was negatively associated with mRNA expression in leg muscle (P = 0.0124), indicating that DNA methylation may be negatively associated with the expression of HSP70, although the difference was not significant. We concluded that the expression of HSP70 is heat inducible and tissue dependent and that heat induction may correlate with DNA methylation pattern in the HSP70 promoter, whereas tissue dependence is unrelated to DNA methylation pattern.

The relationship between gene expression of cationic and neutral amino acid transporters in the small intestine of chick embryos and chick breed, development, sex, and egg amino acid concentration.

This study was conducted to investigate the gene expression of cationic and neutral amino acid (AA) transporters in the small intestine of chick embryos with different genetic backgrounds [Wenshi Yellow-Feathered chick (WYFC) and White Recessive Rock chick (WRRC)]. The study also investigated the correlation between the abundance of AA transporter mRNA and the AA content of fertilized eggs. Intestinal samples were collected on embryonic d 9, 12, 14, 17, and 19 and the day of hatch. The results showed that, before incubation, the AA content of WRRC eggs was lower (P < 0.05) than the AA content of WYFC eggs. In WYFC, the mRNA abundance of CAT-1 [solute carrier (SLC) family 7 member 1], CAT-4 (SLC family 7 member 4), rBAT (SLC family 3 member 1), y(+)LAT-1 (SLC family 7 member 7), y(+)LAT-2 (SLC family 7 member 6), LAT-4 (SLC family 43 member 2), and SNAT-2 (SLC family 38 member 2), as detected by real-time reverse transcriptase PCR, was greater (P < 0.05) than the mRNA abundance detected in the WRRC samples. The mRNA abundance of all measured AA transporters was affected (P < 0.05) by embryonic age. Sex had the largest effect (P < 0.05) on the mRNA expression of CAT-1, CAT-4, y(+)LAT-2, and LAT-4 in WYFC and on CAT-4 and B(0)AT-1 (SLC family 6 member 19) mRNA expression in WRRC. In WYFC, only CAT-1 mRNA expression was negatively correlated (r = -0.68 to -0.84, P < 0.05) with all AA content. However, few correlations were detected between AA content and the mRNA expression of multiple transporters in WRRC. These findings provide a comprehensive profile of the temporal and spatial mRNA expression of AA transporters in the small intestine of chick embryos. Few correlations were detected between the AA content of the eggs and mRNA expression of specific AA transporters in the small intestine.

Tissue and allelic-specific expression of hsp70 gene in chickens: basal and heat-stress-induced mRNA level quantified with real-time reverse transcriptase polymerase chain reaction.

1. The 70 kDa heat shock proteins (hsp70) are a family of molecular chaperones, which promote protein folding and participate in many cellular functions. The objective of the current research was to investigate the relationship between tissue or allele and the expression of chicken hsp70 under normal growth conditions and during acute heat stress (44 degrees C for 4 h). 2. A total of 279 individuals were genotyped for two single nucleotide polymorphisms (A258G and C276G) in chicken hsp70 gene by single-strand conformation polymorphism (SSCP) analysis. 3. The mRNA abundance of chicken hsp70 genes was evaluated by real-time reverse transcriptase polymerase chain reaction (RT-PCR). The expression of hsp70 gene in the liver (9.83 +/- 0.84, 10(7)) was significantly higher than that in the muscle (4.42 +/- 0.36, 10(7)) under normal growth conditions. However, during acute heat stress, the expression of hsp70 gene in the brain (1.82 +/- 0.25, 10(9)) was the highest and was significantly different from those in the liver (1.08 +/- 0.16, 10(9)) and muscle (1.08 +/- 0.13, 10(9)). 4. The expression of hsp70 among different genotypes or haplotype combinations is quite different under normal and heat-stress conditions. The haplotype H3 (GC) is probably advantageous to improving heat resistance of chickens. 5. The results from the present study indicate that the expression of hsp70 in chickens is affected by heat stress, and is tissue- and allele-dependent.