Shangzhong Xu

SNPs identification and its correlation analysis with milk somatic cell score in bovine MBL1 gene

The objective of this study was to investigate the single nucleotide polymorphisms (SNPs) within bovine binding lectin-liver (A) gene (MBL1) and to explore its correlation analysis with milk somatic cell score (SCS) which reflects mastitis resistance in cattle. Through polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), created restriction site-PCR (CRS-PCR) and DNA sequencing methods, three allelic variant corresponding to the G→A mutation at c.1252G>A in intron1, G→A mutation at c.2534G>A and T→C mutation at c.2569T>C in exon2 of bovine MBL1 gene, could be detected, respectively. The c.2534G>A was a nonsynonymous mutation, resulting in Valine (Val) to Isoleucine (Ile) amino acid replacement (p.Val24Ile). The correlation analysis between the MBL1 SNPs gene and milk SCS were analyzed and a significant correlation with milk SCS was detected in c.2534G>A. The value of milk SCS for individuals with genotype GG was significantly lower than those of genotype GA and AA. Results showed that genotype GG with the lowest milk SCS was favorable for mastitis resistance, whereas genotype AA with the highest milk SCS was easily for mastitis susceptibility. Although more investigations are needed to better clarify the role of these SNPs on mastitis resistance, MBL1 polymorphism appears to be a promising indirect marker to improve dairy mastitis resistance traits in cattle.

Effects of DGAT1 gene on meat and carcass fatness quality in Chinese commercial cattle

This study was designed to investigate the candidate single nucleotide polymorphisms (SNPs) in the exon’s region of bovine diacylglycerol O-acyltransferase (DGAT1) gene using bioinformatics and experimental methods. A total of 17 SNPs were screened from public data resources and DNA sequencing. Three SNPs (c.572A>G, c.1241C>T and c.1416T>G) of these candidate SNPs were genotyped by created restriction site-polymerase chain reaction (CRS-PCR) methods. The gene-specific SNP markers and their effects on meat and carcass fatness quality traits were evaluated in Chinese commercial cattle. The c.572A>G and c.1416T>G significantly effected on backfat thickness, longissimus muscle area, marbling score, fat color and Warner-Bratzler shear force. No significant association was detected between the c.1241C>T and measured traits. Results from this study suggested that the SNP markers may be effective for the marker-assisted selection of meat and carcass fatness quality traits, and added new evidence that DGAT1 gene is an important candidate gene for the improvement of meat and carcass fatness quality in beef cattle industry.

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 theTG 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 theTG-gene-specific SNP may be a useful marker for meat quality traits in future marker-assisted selection programmes in beef cattle.

BRCA1: a new candidate gene for bovine mastitis and its association analysis between single nucleotide polymorphisms and milk somatic cell score

Bovine mastitis is a very complex and common disease of dairy cattle and a major source of economic losses to the dairy industry worldwide. In this study, the bovine breast cancer 1, early onset gene (BRCA1) was taken as a candidate gene for mastitis resistance. The main object of this study was to investigate whether the BRCA1 gene was associated with mastitis in cattle. Through DNA sequencing, Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) and Created Restriction Site PCR (CRS-PCR) methods, three SNPs (G22231T, T25025A, and C28300A) were detected and twenty-four combinations of these SNPs were observed. The single SNP and their genetic effects on somatic cell score (SCS) were evaluated and a significant association with SCS was found in C28300A. The mean of genotype EE was significantly lower than those of genotypes EF and FF. The results of combined genotypes analysis of three SNPs showed that BBDDFF genotype with the highest SCS were easily for the mastitis susceptibility, whereas AACCEE genotype with the lowest SCS were favorable for the mastitis resistance. The information provided in the present study will be very useful for improving mastitis resistance in dairy cattle by marker-assisted selection.

Toll-like receptor 2 gene polymorphism and its relationship with SCS in dairy cattle.

Toll-like receptor 2 (TLR2) plays an important role in the innate immune response to a variety of pathogens. In this study, bovine TLR2 gene was taken as a candidate gene for mastitis resistance. Through PCR-SSCP analysis and sequencing, three missense mutations at T385 G, G398A, and G1884A were detected in the coding region that encoded extracellular domain. Altogether 240 dairy cattle of three breeds (Holstein, Simmental, and Sanhe cattle) were genotyped and allele frequencies were determined. The effects of TLR2 polymorphisms on somatic cell score (SCS) were analyzed and significant association was found between T385 G and SCS. The mean of genotype GG was significantly lower than those of genotype TT and TG. No significant associations were found with SCS for G398A and G1884A. Information provided in this research will be useful in further studies to determine the role of TLR2 gene in the mastitis resistance.

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

Thyroid hormones play an important role in regulating metabolism and can affect 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 T354C, G392A, A430G and T433G SNP markers were significantly associated with marbling score (Pxa0<xa00.05). Animals with the new homozygote genotype had higher marbling score than those with the other genotypes. Otherwise, the linkage disequilibrium analysis indicated that these four SNPs were completely linked (r2xa0=xa01). Results from this study suggest that TG gene-specific SNP may be a useful marker for meat quality traits in future marker assisted selection programs in beef cattle.

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 Axa0→xa0G 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.

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 2xa0months old and the others were retained as normal intact bulls. All animals were slaughtered at 22xa0months old. The results showed that bulls carcass had higher weight (Pxa0<xa00.05), dressing percentages and bigger longissimus muscle areas (Pxa0<xa00.05) than steers. But steer meat had lower shear force values and was fatter (Pxa0<xa00.05) 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.

Association analysis of PRKAG3 gene variants with carcass and meat quality traits in beef cattle

The bovine PRKAG3 gene encodes a muscle-specific isoform of the regulatory gamma-subunit of adenosine monophosphate activated protein kinase (AMPK), which plays a key role in regulating energy homeostasis in eukaryotes. It is well known that mutations in the PRKAG3 gene affect high glycogen content in the porcine skeletal muscle and, consequently, meat quality. Therefore, this gene has been proposed as a positional and functional candidate gene for a quantitative trait locus (QTL) with an effect on meat quality traits. In this study, we detected four single nucleotide polymorphisms (SNPs) at the PRKAG3 gene (DQ082736) in 267 beef cattle. The SNP marker association analysis indicated that the SNP markers T2885C was significantly associated with tenderness trait. Animals with the TT genotype had lower Warner-Bratzler shear force (WBS) than those with the other genotypes. Results of this study suggest that the PRKAG3-gene-specific SNP may be a useful marker for meat quality traits in future marker-assisted selection programmes in beef cattle. Key words : Association analysis, beef cattle, single nucleotide polymorphism (SNP) polymorphism, PRKAG3 gene.

Association of Calpain 1 (CAPN1) and HRSP12 allelic variants in beef cattle with carcass traits

Calpain 1 (CAPN1) and its activator HRSP12 are evaluated as candidate gene for quantitative trait loci (QTLs) affecting meat tenderness. In this study, SNPs were detected by sequencing in 323 cattle from 9 breeds. The association results showed that the A3553G and T824C loci individually related with marbling and tenderness, and CAPN1/HRSP12 double homozygote and heterozygote/homozygote pairs (AA/TT, AA/CC, AG/TT and GG/TT) had higher marbling score than the other groups. Our findings suggest that polymorphisms in CAPN1 and HRSP12 might be the important genetic factor influencing meat quality in carcass trait. Key words : Cattle, Calpain 1, HRSP12, association, carcass trait.