Dexiang Zhang

Polymorphisms of Vasoactive Intestinal Peptide Receptor-1 Gene and Their Genetic Effects on Broodiness in Chickens

Broodiness is a polygenic trait controlled by a small number of autosomal genes. Vasoactive intestinal peptide receptor-1 (VIPR-1) gene could be a candidate of chicken broodiness, and its genomic variations and genetic effects on chicken broodiness traits were analyzed in this study. The partial cloning and sequencing of the VIPR-1 gene showed that the average nucleotide diversity was 0.00669 +/- 0.00093 in Red Jungle Fowls (RJF), and 0.00582 +/- 0.00026 in domestic chickens. One hundred twenty-eight variation sites were identified in the 11,136-bp region of the chicken VIPR-1 gene. Twenty variation sites were genotyped using PCR-RFLP or PCR method to analyze average diversity, linkage-disequilibrium pattern, and haplotype structure in RJF, Xinghua chickens, Ningdu Sanhuang chickens, Baier Huang chickens, and Leghorn Layers. The RJF, Xinghua, Ningdu Sanhuang, and Baier Huang exhibited distinct characteristic of decreasing r(2) value over physical distance. Haplotype analyses showed that some variation sites of the 27-kb region from exon 6 to exon 11 could be associated with broodiness. The distribution of genotypic and allelic frequencies, and heterozygosities in the above 5 populations showed that A-284G, A+457G, C+598T, D+19820I, C+37454T, C+42913T, and C+53327T might be associated with broodiness. The 7 sites and the other 4 sites were genotyped in 644 NDH individuals under cage condition and were used for association analyses between each site and chicken broodiness traits. A significant association (P < 0.05) was found between C+598T in intron 2 and broody frequency (%). Another significant association (P < 0.05) was found between C+53327T and duration of broodiness, in which allele C was positive for DB.

Genetic effects of polymorphisms in candidate genes and the QTL region on chicken age at first egg

BackgroundThe age at first egg (AFE), an important indicator for sexual maturation in female chickens, is controlled by polygenes. Based on our knowledge of reproductive physiology, 6 genes including gonadotrophin releasing hormone-I (GnRH-I), neuropeptide Y (NPY), dopamine D2 receptor (DRD2), vasoactive intestinal polypeptide (VIP), VIP receptor-1 (VIPR-1), and prolactin (PRL), were selected as candidates for influencing AFE. Additionally, the region between ADL0201 and MCW0241 of chromosome Z was chosen as the candidate QTL region according to some QTL databases. The objective of the present study was to investigate the effects of mutations in candidate genes and the QTL region on chicken AFE.ResultsMarker-trait association analysis of 8 mutations in those 6 genes in a Chinese native population found a highly significant association (P < 0.01) between G840327C of the GnRH-I gene with AFE, and it remained significant even with Bonferroni correction. Based on the results of the 2-tailed χ2 test, mutations T32742394C, T32742468C, G32742603A, and C33379782T in the candidate QTL region of chromosome Z were selected for marker-trait association analysis. The haplotypes of T32742394C and T32742468C were significantly associated (P < 0.05) with AFE. Bioinformatics analysis indicated that T32742394C and T32742468C were located in the intron region of the SH3-domain GRB2-like 2 (SH3GL2) gene, which appeared to be associated in the endocytosis and development of the oocyte.ConclusionThis study found that G840327C of the GnRH-I gene and the haplotypes of T32742394C-T32742468C of the SH3GL2 gene were associated with the chicken AFE.

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.

The dopamine D2 receptor gene polymorphisms associated with chicken broodiness

Chicken broodiness is a polygenic trait controlled by autosomal genes. Prolactin gene is a candidate of great interest in molecular studies of broodiness. However, another candidate dopamine D2 receptor (DRD2) gene has not been studied extensively. The objective of this study was to analyze the genetic effects of the DRD2 gene on chicken broodiness through linkage disequilibrium analyses, tag SNP selection, genetic diversity observation, 2-tailed test, and association analyses. In this study, we assayed 27 variations of this gene in 456 individuals from 6 chicken populations to observe linkage disequilibrium pattern, the tag SNP, and genetic diversity. Among the 6 populations, Taihe Silkies exhibited no characteristic between the square of the correlation coefficient of gene frequencies (r(2)) and physical distance. The other populations including Red Jungle Fowls, Xinghua chickens, Ningdu Sanhuang chickens (NDH), Baier Huang chickens, and Leghorn layers exhibited conspicuous characteristic of decreasing r(2) value over physical distance. Linkage disequilibrium decayed more rapidly in Red Jungle Fowls, Xinghua, and NDH than in Baier Huang and Leghorn layers. Allelic frequencies and genotype distributions in the 5 populations showed that A-38600G, I-38463D, T-32751C, A-16105G, A-6543G, C-6539T, and A+2794G were possibly associated with broodiness. Besides the above 7 sites, another 2 sites that might be associated with broodiness were screened by 2-tailed test. All 9 sites were used for association analyses with broodiness in 644 NDH chickens. A significant association (P < 0.05) was found between A-16105G and broody frequency (%), and the T+619C in intron 1 was significantly associated with duration of broodiness (P < 0.05). These findings suggested that the DRD2 gene should be included in future genetic studies of chicken broodiness and 2 SNP of A-16105G and T+619C might be markers for breeding against broodiness.

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.

SNP mapping of QTL affecting growth and fatness on chicken GGA1

An F2 chicken population was established from a crossbreeding between a Xinghua line and a White Recessive Rock line. A total of 502 F2 chickens in 17 full-sib families from six hatches was obtained, and phenotypic data of 488 individuals were available for analysis. A total of 46 SNP on GGA1 was initially selected based on the average physical distance using the dbSNP database of NCBI. After the polymorphism levels in all F0 individuals (26 individuals) and part of the F1 individuals (22 individuals) were verified, 30 informative SNP were potentially available to genotype all F2 individuals. The linkage map was constructed using Cri-Map. Interval mapping QTL analyses were carried out. QTL for body weight (BW) of 35 d and 42 d, 49 d and 70 d were identified on GGA1 at 351–353 cM and 360 cM, respectively. QTL for abdominal fat weight was on GGA1 at 205 cM, and for abdominal fat rate at 221 cM. Two novel QTL for fat thickness under skin and fat width were detected at 265 cM and 72 cM, respectively.

Chicken GHR natural antisense transcript regulates GHR mRNA in LMH cells

Growth hormone receptor (GHR) played key roles in human and animal growth. Both human laron type dwarfism and sex linked dwarf chicken were caused by the mutation of GHR gene. In this study, we identified an endogenously expressed long non-coding natural antisense transcript, GHR-AS, which overlapped with the GHR mRNA (GHR-S) in a tail to tail manner. Spatial and temporal expression analyses indicated that GHR-AS were highly expressed in chicken liver and displayed ascending with the development of chicken from E10 to 3 w of age. Interfering GHR-AS caused GHR-S decreasing, accompanied with increasing of the inactive gene indicator, H3K9me2, in the GHR-S promoter regions in LMH cells. RNase A experiment exhibited that GHR-AS and GHR-S can form double strand RNAs at the last exon of GHR gene in vivo and in vitro, which hinted they could act on each other via the region. In addition, the levels of GHR-S and GHR-AS can be affected by DNA methylation. Compared the normal chicken with the dwarfs, the negative correlation trends were showed between the GHR-S promoter methylation status and the GHR-AS levels. This is the first report of that GHR gene possessed natural antisense transcript and the results presented here further highlight the fine and complicated regulating mechanism of GHR gene in chicken development.

Effect of the C.–1 388 A>G polymorphism in chicken heat shock transcription factor 3 gene on heat tolerance

Abstract Heat stress is one of the main factors that influence poultry production. Heat shock proteins (HSPs) are known to affect heat tolerance. The formation of HSPs is regulated by heat shock transcription factor 3 ( HSF3 ) in chicken. A DNA pool was established for identifying single nucleotide polymorphisms (SNPs) of the chicken HSF3, and 13 SNPs were detected. The bioinformatic analysis showed that 8 SNPs had the capacity to alter the transcription activity of HSF3. The dual luciferase report gene assay showed that there was a significant difference ( P Firefly luciferase /Renilla luciferase ratio (F/R) of C.–1 703 A>G (S1) and C.–1 388 A>G (S4) sites at the 5′-untranslated region (UTR) of chicken HSF3. The electrophoretic mobility shift assay showed that the S4 site was a transcription binding factor. The analysis of the association of the S1 and S4 sites with heat tolerance index revealed that the S4 site was significantly correlated with the CD 3+ T cell, corticosterone, and T3 levels in Lingshan chickens and with the heterophil/lymphocyte value in White Recessive Rock. These results showed that the S4 site at the 5′ UTR of chicken HSF3 might have an impact on heat tolerance in summer and could be used as a potential marker for the selection of chicken with heat tolerance in the future.

Determination of Residual Feed Intake and Its Associations with Single Nucleotide Polymorphism in Chickens

Marker assisted selection (MAS) for residual feed intake (RFI) is considered to be one of the powerful means to improve feed conversion efficiency, and therefore reduce production costs. To test the inner relationship among body compositions, growth traits and RFI, four models were proposed to assess the extensively explanatory variables accounting for partial variables in feed intake besides metabolic body weight and growth rate. As a result, the original model (Kochs model) had the lowest R2 (80.78%) and the highest Bayesian information criterion (1 323.3) value among the four models. Moreover, the effects on RFI caused by single nucleotide polymorphisms (SNPs) were assessed in this study. Twelve SNPs from 7 candidate genes were genotyped in 2 Chinese native strains. rs14743490 of RPLP2 gene showed suggestively significant association with initial body weight in both strains (P<0.10). rs15047274 of TAF15 was significantly associated with growth weight, final weight, and feed intake (P<0.05) in N301 strain, in contrast, it was only suggestively significant associated with feed intake (P<0.10) in N414 strain. rs15869967 was significantly associated with RFI in N414 strain but not in N301 strain. This study has identified potential genetic markers suitable for MAS in improving the above mentioned traits, but these associations need to be rectified in other larger populations in future.

The Effects of Different Sex-Linked Dwarf Variations on Chinese Native Chickens

Abstract Variants in chicken growth hormone receptor (GHR) gene lead to sex-linked dwarf (SLD) chickens, but effects of different variants are distinct. In this study, 11 SLD chicken breeds or strains including 3 Chinese native breeds and 8 breeding strains were studied in order to investigate the effects of different sex-linked dwarf variations on growth performance. The results showed that there were three reasons which could lead to dwarfism in the 11 breeds or strains. Firstly, an about 1.7 kb deletion of growth hormone receptor (GHR) gene leads to dwarfism in Jiangxi dwarf chicken, strains GF24, GF26, N308, N309, and N310. Secondly, a T354C mutation in exon 5 of the GHR gene leads to dwarfism in strains N301 and N305. Thirdly, an unknown variant leads to dwarfism in Guizhou Yellow Dwarf chicken and Yixing Bantam chicken. In addition, all individuals of N303 had the 1.7 kb deletion of the GHR gene, and additionally, some of them also carried the T354C mutation. As far as the performance of individuals were compared among T354C homozygote, deletion homozygote, and heterozygote carrying both T354C and deletion, it was found that the T354Cs impacts on body weight of Chinese chickens were maximum, the body weight of chickens with homozygote T354C was 92.12% of those with heterozygote, and the difference of the body weight between deletion homozygote and heterozygote was not significant. There was no significant difference of shank length among three genotypes.