Effect of castration on carcass quality and differential gene expression of longissimus muscle between steer and bull.

The effect of castration on carcass quality was investigated by ten Chinese Simmental calves. Five calves were castrated randomly at 2 months old and the others were retained as normal intact bulls. All animals were slaughtered at 22 months old. The results showed that bulls carcass had higher weight (P < 0.05), dressing percentages and bigger longissimus muscle areas (P < 0.05) than steers. But steer meat had lower shear force values and was fatter (P < 0.05) than bull. Furthermore, in order to discover genes that were involved in determining steer meat quality, we compared related candidate gene expression in longissimus muscle between steer (tester) and bull (driver) using suppressive subtractive hybridization. Ten genes were identified as preferentially expressed in longissimus muscle of steer. The expression of four selected differentially expressed genes was confirmed by quantitative real-time PCR. Overall, a 1.96, 2.41, 2.89, 2.41-fold increase in expression level was observed in steer compared with bull for actin, gamma 2, smooth muscle, tropomyosin-2, insulin like growth factor 1 and hormone-sensitive lipase, respectively. These results implied that these differentially expressed genes could play an important role in the regulation of steer meat quality.

Single nucleotide polymorphism of CACNA2D1 gene and its association with milk somatic cell score in cattle.

The objective of the present study was to identify polymorphisms of the CACNA2D1 gene, and to analyze associations between these polymorphisms and mastitis in several cattle breeds. Through PCR-RFLP methods and DNA sequencing, an allelic variant corresponding to the A→G mutations and Aspartic (Asp) to Glycine (Gly) amino acid replacement at positions 526745 in the exon 25 of bovine CACNA2D1 gene could be detected. Two alleles, A and G, and three genotypes, AA, AG and GG were defined. Genetic character in the studied populations indicated that the A526745G loci of CACNA2D1 gene was moderate polymorphism and fitted with Hardy-Weinberg equilibrium (P > 0.05). The effects of CACNA2D1 polymorphisms on somatic cell score (SCS) were analyzed and significant association was found between A526745G and SCS. The mean of genotype GG was significantly lower than those of genotype AG and AA (P = 0.0469). Information provided in this research could be useful in further studies to determine the role of CACNA2D1 gene in the mastitis resistance.

CAG-repeat variant in the polymerase γ gene and male infertility in the Chinese population: a meta-analysis.

Several studies have reported a relationship between the length of the CAG-repeat in the polymerase γ (POLG) gene and male infertility. However, other studies have not reproduced this result. In our study, the POLG-CAG-repeat length was analyzed in 535 healthy individuals from six Chinese Han populations living in different provinces. The frequencies of 10-CAG alleles and genotypes were high (97.38 and 94.13%, respectively), with no significant difference among the six Chinese Han populations. Furthermore, we determined the distribution of the POLG-CAG-repeat in 150 infertile men and 126 fertile men. Our study suggested that the distributions of POLG-CAG-repeat alleles and genotypes were not significantly different between infertile (95.67 and 92.67%, respectively) and fertile men (97.22 and 94.44%, respectively). In a subsequent meta-analysis, combining our data with data from previous studies, a comparison of the CAG-repeat alleles in fertile versus infertile men showed no obvious risk for male infertility associated with any particular allele (pooled odds ratio (OR)=0.94; 95% confidence interval (CI): 0.60-1.48). The significance level was not attained with any of the following genetic models: homozygote comparison (not 10/not 10 versus 10/10: OR=1.34; 95% CI: 0.66-2.72), heterozygote comparison (10/not 10 versus 10/10: OR=1.04; 95% CI: 0.78-1.38), dominant model comparison (not 10/not 10+10/not 10 versus 10/10: OR=1.08; 95% CI: 0.79-1.47) and recessive genetic comparison (not 10/not 10 versus 10/not 10+10/10: OR=1.31; 95% CI: 0.68-2.55). In conclusion, there is no significant difference of the frequencies of POLG-CAG-repeat variants among six Chinese Han populations, and this polymorphism may not be associated with Chinese male infertility. On the basis of a meta-analysis, there is no obvious association between CAG-repeat variants of the POLG gene and male infertility.

Genetic polymorphisms of the CACNA2D1 gene and their association with carcass and meat quality traits in cattle.

The objective of this study was to identify genetic polymorphisms of the CACNA2D1 gene and to analyze associations between SNPs and carcass and meat quality traits in cattle. Through PCR-RFLP and DNA sequencing methods, a new allelic variant corresponding to the A --> G mutation (aspartic to glycine amino acid replacement) of the bovine CACNA2D1 gene was detected. Two alleles and three genotypes (AA, AG, and GG) were defined. Genetic character indicated that the A526745G locus showed moderate polymorphism and was in Hardy-Weinberg equilibrium. Gene-specific SNP marker association analysis showed that the A526745G mutant was significantly associated with carcass weight, dressing percentage, meat percentage, and backfat thickness. The results add new evidence that CACNA2D1 is an important candidate gene for the selection of carcass and meat quality traits in the cattle industry.

Polymorphisms in MC4R gene and correlations with economic traits in cattle.

MC4R contributes to the control of food intake and energy expenditure, and single nucleotide polymorphisms (SNPs) in the MC4R gene have clearly been associated with backfat depth, feed intake and growth rate in pig. Our objectives were to scan the complete coding region by sequencing in samples from eight cattle breeds, to estimate the frequency of the SNPs in the MC4R gene and to determine if individual genotypes were associated with several economic traits. Five polymorphisms were detected at position 19 (C/A), 20 (A/T), 83(T/C), 128 (G/A), and 1069 (G/C), and the last one was significantly associated with backfat thickness value (P < 0.01, n = 245). The linkage disequilibrium analysis indicated that the SNP markers C19A, A20T, T83C and G128A were completely linked (r (2) = 1).

[Analysis of the 14 bp insertion/deletion polymorphism in human leukocyte antigen-G gene in Chinese Dai and Han ethnic groups in Yunnan Province].

A 14 bp insertion/deletion polymorphism (+14 bp/-14 bp) in exon 8 of HLA-G gene has been investigated extensively because this polymorphism was associated with HLA-G mRNA stability and could influence HLA-G mRNA expression. In the present study, we genotyped 14 bp insertion/deletion polymorphisms in the HLA-G gene in Dai and Han populations in Yunnan Province. The frequencies of +14 bp in Dai and Han were 31.97% and 40.87%, respectively. The frequency of +14 bp/+14 bp in Dai was lower (8.20%) than that of Han (17.31%). Nevertheless, the frequency of +14 bp/-14 bp was similar in both populations (47.54% in Dai and 47.11% in Han). When compared with other populations, the frequency of 14 bp insertion/deletion of Han was similar to others, whereas the Dai showed significant difference from others and presented it's specific characteristic. We assumed that the distribution characteristic of 14 bp insertion/deletion in Dai might be the results of random genetic drift, but the role of natural selection cannot be excluded.

Association analysis of thyroglobulin gene variants with carcass and meat quality traits in beef cattle.

Thyroid hormones play an important role in regulating the metabolism and can affect the homeostasis of fat deposition. The gene encoding thyroglobulin (TG), producing the precursor for thyroid hormones, has been proposed as a positional and functional candidate gene for a QTL with an effect on fat deposition. In the present study, we identified 6 novel SNPs at the 3' flanking region of the TG gene. The SNP marker association analysis indicated that the SNP markers G133C, G156A, C220T and A506C were significantly associated with marbling score (P<0.05, N=271). Animals with the new homozygote genotype had higher marbling scores than those with the other genotypes. Besides, the linkage disequilibrium analysis indicated that these 4 SNPs were completely linked (r2 = 1). Results of this study suggest that the TG-gene-specific SNP may be a useful marker for meat quality traits in future marker-assisted selection programmes in beef cattle.

[Genetic variation in RXRG gene and its relationship with twinning trait in cattle].

Retinoic X receptor-gamma (RXRG) gene was studied as a candidate gene for the twinning trait of bovine. A new SNP A1941G was detected by sequencing at 3'UTR. Different genotypes were determined in Luxi monotocous cows, Luxi twinning cows, Chinese Simmental cows, Angus cows and Simmental x Mongolia cows by restriction fragment length polymorphism (RFLP). The value of polymorphism information content indicated that this was a moderate polymorphism in Luxi monotocous cows and Luxi twinning cows. The chi(2) test indicated that the polymorphic locus in Luxi twinning cows did not fit Hardy-Weinberg equilibrium (Plt;0.05). The chi(2) test of associational analysis between genotypic distribution and twinning or monotocous trait in Luxi cows showed that the difference was very significant (Plt;0.01).

[Genetic variation in the 5' flanking region of bovine TLR4 gene and correlation with mastitis].

Toll-like receptor 4 recognizes pathogen ligands and mediates signaling to initiate innate and adaptive immune responses. In this experiment, a 477 bp segment of the 5'-flanking region of TLR4 gene of Chinese Holstein, Sanhe cattle and Chinese simmental was amplified by polymerase chain reaction. After sequencing, a polymorphic site in amplified production of TLR4 was identified of having either a G or a C at position 245. This polymorphism in the three populations was detected by digesting the fragment with restriction endonuclease Msp I. Results showed that both alleles (A and B) were found in the three populations and the value of polymorphism information content indicated that this was a moderate polymorphism. Chi2 test indicated that the polymorphism locus in Sanhe cattle did not fit Hardy-Weinberg equilibrium (P< 0.05). In addition, the effect of the TLR4 polymorphism on somatic cell score was analyzed, and the results indicated that the somatic cell score were significantly affected by lactation month and the type of breeds(P<0.05), but not by different genotypes (P > 0.05).

[Analysis of mitochondrial 12S rRNA gene polymorphism in cattle].

The mitochondrial DNA 12S rRNA in seven Chinese local yellow cattle breeds, one cultivated breed and three imported breeds was studied by single-strand conformation polymorphism (SSCP). Three haplotypes (I, II , III) were detected, with haplotype I found only in one cattle of the Jinnan breed. Haplotype II did not appear in the foreign cattle breeds and low in Chinese-Simmental breed but was rich in Chinese local breeds. Haplotype III had the widest distribution and was present in ten cattle breeds. The average polymorphism information content (PIC) for Chinese cattle between 0.232-0.423 was modest, which suggested relative abundance of genetic resources for the Chinese native cattle.