Lack of association between CAST SNPs and meat tenderness in sheep

Effects of polymorphisms in CAPN1 and CAST genes on meat tenderness of Chinese Simmental cattle

Considerable evidence has demonstrated that the μ -calpain (CAPN1) gene and its inhibitor calpastatin (CAST) gene are major factors affecting meat quality. Marker-assisted selection (MAS) has been widely used to improve beef quality traits. Therefore, the objective of the present study was to investigate the single nucleotide polymorphisms (SNPs) of bovine CAPN1 and CAST genes using 367 animals representing the four main Chinese cattle breeds and to explore the effects of these SNPs on meat quality traits. Two SNPs within CAPN1 and one SNP in CAST were successfully identified in cattle. Genetic diversity analyses suggested that most SNPs in the four breeds exhibited a moderate genetic diversity. Moreover, associations between individual markers and meat quality traits were analyzed in Chinese Simmental cattle. The CAPN1 4558 A > G locus was found to be significantly associated with shear force value (SFV) and marbling score (BMS), and CAPN1 4684 C > T exerted a significant effect on SFV, while the CAST genotype was not significantly associated with any of the measured traits. SFV, commonly used to measure meat tenderness, represents an important quality trait as it contributes to the flavor of cooked meat. This work confirms the effect of CAPN1 on beef tenderness and lays an important foundation for future cattle breeding.

Detecting novel SNPs and breed-specific haplotypes at calpastatin gene in Iranian fat- and thin-tailed sheep breeds and their effects on protein structure

Calpastatin has been introduced as a potential candidate gene for growth and meat quality traits. In this study, genetic variability was investigated in the exon 6 and its intron boundaries of ovine CAST gene by PCR-SSCP analysis and DNA sequencing. Also a protein sequence and structural analysis were performed to predict the possible impact of amino acid substitutions on physicochemical properties and structure of the CAST protein. A total of 487 animals belonging to four ancient Iranian sheep breeds with different fat metabolisms, Lori-Bakhtiari and Chall (fat-tailed), Zel-Atabay cross-bred (medium fat-tailed) and Zel (thin-tailed), were analyzed. Eight unique SSCP patterns, representing eight different sequences or haplotypes, CAST-1, CAST-2 and CAST-6 to CAST-11, were identified. Haplotypes CAST-1 and CAST-2 were most common with frequency of 0.365 and 0.295. The novel haplotype CAST-8 had considerable frequency in Iranian sheep breeds (0.129). All the consensus sequences showed 98-99%, 94-98%, 92-93% and 82-83% similarity to the published ovine, caprine, bovine and porcine CAST locus sequences, respectively. Sequence analysis revealed four SNPs in intron 5 (C24T, G62A, G65T and T69-) and three SNPs in exon 6 (c.197A>T, c.282G>T and c.296C>G). All three SNPs in exon 6 were missense mutations which would result in p.Gln 66 Leu, p.Glu 94 Asp and p.Pro 99 Arg substitutions, respectively, in CAST protein. All three amino acid substitutions affected the physicochemical properties of ovine CAST protein including hydrophobicity, amphiphilicity and net charge and subsequently might influence its structure and effect on the activity of Ca2+ channels; hence, they might regulate calpain activity and afterwards meat tenderness and growth rate. The Lori-Bakhtiari population showed the highest heterozygosity in the ovine CAST locus (0.802). Frequency difference of haplotypes CAST-10 and CAST-8 between Lori-Bakhtiari (fat-tailed) and Zel (thin-tailed) breeds was highly significant (P<0.001), indicating that these two haplotypes might be breed-specific haplotypes that distinguish between fat-tailed and thin-tailed sheep breeds.

An independent validation association study of carcass quality, shear force, intramuscular fat percentage and omega-3 polyunsaturated fatty acid content with gene markers in Australian lamb

Previous association studies revealed several single nucleotide polymorphisms (SNPs) that explained the observed phenotypic variation for meat tenderness and long-chain omega-3 polyunsaturated fatty acid (PUFA) content of Australian lamb. To confirm the validity of these associated SNPs at predicting meat tenderness and omega-3 PUFA content, an independent validation study was designed. The OvineSNP50 genotypes of these animals were used to impute the 192 SNP Meat Quality Research (MQR) panel genotypes on nearly 6200 animals from the Cooperative Research Centre for Sheep Industry Innovation Information Nucleus Flock and Sheep Genomics Falkiner Memorial Field Station flock. Association analysis revealed numerous SNP from the 192 SNP MQR panel that were associated with carcass quality - fat depth at the C-site and eye muscle depth; shear force at day 1 and day 5 after slaughter (SF1 and SF5); and omega-3 PUFA content at P<0.01. However, 1 SNP was independently validated for SF5 (i.e. CAST_101781475). The magnitude of the effect of each significant SNP and the relative allele frequencies across Merino-, Maternal- and Terminal-sired progeny was determined. The independently validated SNP for SF5 and the associated SNP with omega-3 PUFA content will accelerate efforts to improve these phenotypic traits in Australian lamb.

Haplotypic diversity within the ovine calpastatin (CAST) gene

Calpastatin (CAST) is a protein inhibitor that acts specifically on calpains and plays a regulatory role in postmortem beef tenderization and muscle proteolysis. Polymorphisms in the bovine CAST gene have been associated with meat tenderness, but little is known about how the ovine CAST gene may affect sheep meat quality traits. In this study, we selected two parts of the ovine CAST gene that have been previously reported to be polymorphic (region 1-part of intron 5 and exon 6, and region 2-part of intron 12), to investigate haplotype diversity across an extended region of the ovine gene. First, we developed a simple and efficient polymerase chain reaction-single-strand conformational polymorphism (PCR-SSCP) method for genotyping region 2, which allowed the detection of a novel allele as well as the three previously reported alleles. Next, we genotyped both regions 1 and 2 of the ovine CAST gene from a large number of sheep to determine the haplotypes present. Nine different haplotypes were found across this extended region of the ovine CAST gene and four haplotypes were identified that suggested historical recombination events within this gene. Haplotypes are typically more informative than single nucleotide polymorphisms (SNPs) for analyzing associations between genes and complex production traits, such as meat tenderness, but the potential for intragenic recombination within the ovine CAST may make finding associations challenging.