New variations in intron 4 of growth hormone gene in Chinese native chickens

Mutations in growth hormone gene affect stability of protein structure leading to reduced growth, reproduction, and milk production in crossbred cattle-an insight

The GH has a multifaceted role in growth, reproduction, and milk production. Nonsynonymous mutations identified as L153V were observed from GH1 (L) to GH2 (V) with higher genotypic frequency for GH1 being 0.87. GH2 (V) allele was identified as a rare allele and the population followed Hardy-Weinberg equilibrium. LL homozygote variant had significantly better growth, reproduction, and expected milk production at different ages in crossbred (CB) males. Reports are scanty explaining the molecular mechanism of how individuals with LV genotype were phenotypically inferior to that of wild-type LL. In the present study, it was explored that GH peptide with LV heterozygotes of GH gene, were observed to have reduced structural stability thermodynamically and thus functionally leads to reduced economic traits in CB animals. The fact was first time reported and confirmed through genomic analysis, bioinformatics, and later confirmed through immunohistochemistry. Differential expression analysis of the GH gene with respect to other genes in the hypothalamus-pituitary growth axis of CB cattle was also studied to have a complete insight of the GH gene.

Genomic diversity dynamics in conserved chicken populations are revealed by genome-wide SNPs

BACKGROUND

Maintaining maximum genetic diversity and preserving breed viability in conserved populations necessitates the rigorous evaluation of conservation schemes. Three chicken breeds (Baier Yellow Chicken (BEC), Beijing You Chicken (BYC) and Langshan Chicken (LSC)) are currently in conservation programs in China. Changes in genetic diversity were measured by heterozygosity, genomic inbreeding coefficients, and autozygosity, using estimates derived from runs of homozygosity (ROH) that were identified using SNPs.

RESULTS

Ninety DNA samples were collected from three generations for each breed. In the most recent generation, the highest genetic diversity was observed in LSC, followed by BEC and BYC. Inbreeding coefficients based on ROH for the three breeds declined slightly between the first and middle generations, and then rapidly increased. No inbreeding coefficients exceeded 0.1. Population structure assessments using neighbor-joining tree analysis, principal components analysis, and STRUCTURE analysis indicated that no genetic differentiation existed within breeds. LD decay and ROH at different cut-off lengths were used to identify traces left by recent or ancient inbreeding. Few long ROH were identified, indicating that inbreeding has been largely avoided with the current conservation strategy. The observed losses in genetic diversity and occurrences of inbreeding might be consequences of sub-optimal effective population sizes.

CONCLUSIONS

The conserved Chinese chicken populations have high genomic diversity under the current conservation program (R: F). Furthermore, this study highlights the need to monitor dynamic changes in genetic diversity in conserved breeds over successive generations. Our research provides new insights into genetic diversity dynamics in conserved populations, and lays a solid foundation for improving conservation schemes.

Association of SNP rs80659072 in the ZRS with polydactyly in Beijing You chickens

The Beijing You chicken is a Chinese native breed with superior meat quality and a unique appearance. The G/T mutation of SNP rs80659072 in the Shh long-range regulator of GGA2 is highly associated with the polydactyly phenotype in some chicken breeds. In the present study, this SNP was genotyped using the TaqMan detection method, and its association with the number of toes was analyzed in a flock of 158 birds of the Beijing You population maintained at the Beijing Academy of Agriculture and Forestry Sciences. Furthermore, the skeletal structure of the digits was dissected and assembled in 113 birds. The findings revealed that the toes of Beijing You chickens were rich and more complex than expected. The plausible mutation rs80659072 in the zone of polarizing activity regulatory sequence (ZRS) in chickens was an essential but not sufficient condition for polydactyly and polyphalangy in Beijing You chickens. Several individuals shared the T allele but showed normal four-digit conformations. However, breeding trials demonstrated that the T allele could serve as a strong genetic marker for five-toe selection in Beijing You chickens.

Polymorphism of growth hormone gene and its association with seminal and sexual behavioral traits in crossbred cattle

The decline in the male reproductive ability in terms of sexual behavior and seminal traits might lead to nonavailability of required number of bulls in a progeny testing program. The present study was conducted in 493 crossbred cattle (Bos taurus × Bos indicus) bulls to study polymorphisms of growth hormone (GH) gene and its association with seminal and sexual behavioral characteristics. A 428-base pair fragment of GH gene spanning over the fourth exon, fourth intron, and fifth exon was amplified and digested with AluI restriction enzyme. Bulls were found to be polymorphic, with two variants, LL and LV, and higher genotypic frequency for LL being 0.88. Twelve nucleotide changes and a single nonsynonymous substitution of Leucine by Valine were observed from GH1 (L) to GH2 (V). Statistical analysis revealed that the genotype of the GH gene had a significant effect on libido score, reaction time, Flehmen response, requirement of mounting stimulus, sperm mass activity, number of semen doses per collection, individual fresh sperm motility, postthaw sperm motility, acrosome integrity, hypo-osmotic swelling test, live and dead count, total morphological abnormality, and head abnormality of sperm in crossbred bulls. Growth hormone gene might be considered a candidate gene for seminal and sexual behavioral traits in crossbred cattle.

An 8bp indel in exon 1 of Ghrelin gene associated with chicken growth

Ghrelin, acts as the endogenous ligand for growth hormone secretagogues receptor (GHS-R), is a novel growth hormone (GH) releasing peptide with reported effects on food intake in chickens. In this study, an 8 bp indel polymorphism in exon 1 of the chicken Ghrelin (cGHRL) gene was genotyped in a F(2) designed full-sib population to analyze its associations with chicken growth and carcass traits. Later, mRNA level in the proventriculus was determined by real-time PCR to reveal the expression feature of cGHRL gene. Result showed that this 8 bp indel was significantly associated with body weight at the age of 28 days (BW28) and 56 days (BW56), eviscerated weight (EW) and leg muscle weight (LMW) (P<0.05), highly significantly associated with hatch weight (HW), BW14, 21, 35, 42, 49, 90 and body length (BL), dressed weight (DW), eviscerated weight with giblet (EWG), wing weight (WW), breast muscle weight (BMW) and head and neck weight (HNW) (P<0.01). Meanwhile, A allele (with 'CTAACCTG') was positive for chicken growth as individuals with AA genotype had the highest value of all traits. Analysis on cGhrelin mRNA level revealed that it differed significantly among individuals with three genotypes (P<0.05). Individuals with AB genotype had the highest mRNA level, whereas that of AA had the lowest one. It was concluded that this 8 bp indel of cGHRL gene was significantly associated with most body weight and body composition traits, and negative effect of endogenous Ghrelin on chicken growth were indicated by this study.

High Diversity of the Chicken Growth Hormone Gene and Effects on Growth and Carcass Traits

The chicken growth hormone (cGH) gene plays a crucial role in controlling growth and metabolism, leading to potential correlations between cGH polymorphisms and economic traits. In this study, DNA from four divergent chicken breeds were screened for single nucleotide polymorphisms (SNPs) in the cGH gene using denaturing high-performance liquid chromatography and sequencing. A total of 46 SNPs were identified, of which 4 were in the 5' untranslated region, 1 in the 3' untranslated region, 5 in exons (two of which are nonsynonymous), with the remaining 36 in introns. The nucleotide diversity in the cGH gene ( theta = 2.7 x 10(-3)) was higher than that reported for other chicken genes, even within the same breeds. The associations of five of these SNPs and their haplotypes with chicken growth and carcass traits were determined using polymerase chain reaction-restriction fragment length polymorphism analysis in a F2 resource population cross of two of the four chicken breeds (White Recessive Rock and Xinghua). This analysis shows that, among other correlations, G+1705A was significantly associated with body weight at all ages measured, shank length at three of four ages measured, and average daily gain within weeks 0 to 4. Thus, this cGH polymorphism, or another polymorphism that is in linkage disequilibrium with G+1705A, appears to correspond to a significant growth-related quantitative trait locus difference between the two breeds used to construct the resource population.