Effect of two non-synonymous ecto-5'-nucleotidase variants on the genetic architecture of inosine 5'-monophosphate (IMP) and its degradation products in Japanese Black beef

Genome-wide association studies of anserine and carnosine contents in the breast meat of Korean native chickens

Histidine-containing dipeptides (HCDs), such as anserine and carnosine, are enormously beneficial to human health and contribute to the meat flavor in chickens. Meat quality traits, including flavor, are polygenic traits with medium to high heritability. Polygenic traits can be improved through a better understanding of their genetic mechanisms. Genome-wide association studies (GWAS) constitute an effective genomic tool to identify the significant single-nucleotide polymorphisms (SNPs) and potential candidate genes related to various traits of interest in chickens. This study identified potential candidate genes influencing the anserine and carnosine contents in chicken meat through GWAS. We performed GWAS of anserine and carnosine using the Illumina chicken 60K SNP chip (Illumina Inc., San Diego, CA) in 637 Korean native chicken-red-brown line (KNC-R) birds consisting of 228 males and 409 females. The contents of anserine and carnosine in breast meat of KNC-R chickens were investigated. The mean value of the anserine and carnosine are 29.12 mM/g and 10.69 mM/g respectively. The genomic heritabilities were moderate (0.24) for anserine and high (0.43) for carnosine contents. Four and nine SNPs were significantly (P < 0.05) associated with anserine and carnosine, respectively. Based on the GWAS result, the 30.6 to 31.9 Mb region on chicken chromosome 7 was commonly associated with both anserine and carnosine. Through the functional annotation analysis, we identified HNMT and HNMT-like genes as potential candidate genes associated with both anserine and carnosine. The results presented here will contribute to the ongoing improvement of meat quality to satisfy current consumer demands, which are based on healthier, better-flavored, and higher-quality chicken meat.

Explorations on Key Module and Hub Genes Affecting IMP Content of Chicken Pectoralis Major Muscle Based on WGCNA

Inosine monophosphate (IMP) is a substance that enhances flavor and plays a crucial role in the umami taste of chicken muscle. It is also an influential factor in determining chicken's economic value. However, the molecular regulatory network underlying the IMP content in muscle remains unclear. To address this issue, we performed transcriptome sequencing on 20 pectoralis major muscle samples from 120-day-old Guangde feathered-leg chicken and used weighted gene co-expression network analysis (WGCNA) to identify key regulatory factors that influence IMP content. The weighted gene co-expression network was constructed using a total of 16,344 genes, leading to the identification of 20 co-expression gene modules. Among the modules that were identified, it was observed that the purple module (R = -0.51, p = 0.02) showed a significant negative correlation with the IMP content. This suggests that the genes within the purple module had the ability to regulate the IMP content. A total of 68 hub genes were identified in the purple module through gene significance (GS) > 0.2 and module membership (MM) > 0.8. The STRING database was used for a protein-protein interaction (PPI) network of hub genes. Furthermore, troponin I type 1 (TNNI1), myozenin 2 (MYOZ2), myosin light chain 2 regulatory cardiac slow (MYL2), and myosin light chain 3 regulatory cardiac slow (MYL3) involved in the "ATP-dependent activity", "cAMP signaling pathway" and "cGMP-PKG signaling pathway" were identified as central regulators that contribute to IMP content. These results offer valuable information into the gene expression and regulation that affects IMP content in muscle.

The effect of common duckweed (Lemna minor L.) extract on the shelf-life of beef burgers stored in modified atmosphere packs: A metabolomics approach

The impact of duckweed extracts (DEs) on the shelf-life of packaged beef burgers was evaluated through classical assays and untargeted metabolomics. Beef burgers were formulated with an antioxidants-free control (CON), 1 g/kg sodium ascorbate (ASC), and increasing levels of a DEs, namely 1 (DE1), 5 (DE5), and 10 (DE10) g/kg, packaged under modified atmosphere and stored at 4 °C for 19 days. The DEs, abundant in phytochemicals, determined no issues with the hygienic status of the product. DEs modulated the redox status, being ineffective in preserving linolenic acid from peroxidation. However, the oxidation marker 2-nonenoic acid was down-accumulated in the DE10 sample following 19 days of storage, recording a lower glutathione:glutathione disulfide ratio. The accumulation of adipate semialdehyde revealed the inefficiency of DEs in coping with protein oxidation, while DEs prevented the accumulation of biogenic amines. Therefore, this work suggests a potential pro-oxidant role of the formulated DEs.

Selection signatures of Qinchuan cattle based on whole-genome sequences

Qinchuan cattle has gradually improved in body shape and growth rate in the long-term breeding process from the draft cattle to beef cattle. As the head of the five local yellow cattle in China, the Qinchuan cattle has been designated as a specialized beef cattle breed. We investigated the selection signatures using whole genome sequencing data in Qinchuan cattle. Based on Fst, we detected hundreds of candidate genes under selection across Qinchuan, Red Angus, and Japanese Black cattle. Through protein-protein interaction analysis and functional annotation of candidate genes, the results revealed that KMT2E, LTBP1 and NIPBL were related to brain size, body characteristics, and limb development, respectively, suggesting that these potential genes may affect the growth and development traits in Qinchuan cattle. ARIH2, DACT1 and DNM2, et al. are related to meat quality. Meanwhile, TBXA2R can be used as a gene associated with reproductive function, and USH2A affect coat color. This provided a glimpse into the formation of breeds and molecular genetic breeding. Our findings will promote genome-assisted breeding to improve animal production and health.

Genome-Wide Association Study on the Content of Nucleotide-Related Compounds in Korean Native Chicken Breast Meat

Meat flavor is an important factor that influences the palatability of chicken meat. Inosine 5'-monophosphate (IMP), inosine, and hypoxanthine are nucleic acids that serve as taste-active compounds, mainly enhancing flavor in muscle tissue. For this study, we performed a genome-wide association study (GWAS) using a mixed linear model to identify single-nucleotide polymorphisms (SNPs) that are significantly associated with changes in the contents of the nucleotide-related compounds of breast meat in the Korean native chicken (KNC) population. The genomic region on chicken chromosome 5 containing an SNP (rs316338889) was significantly (p < 0.05) associated with all three traits. The trait-related candidate genes located in this significant genomic region were investigated through performing a functional enrichment analysis and protein-protein interaction (PPI) database search. We found six candidate genes related to the function that possibly affected the content of nucleotide-related compounds in the muscle, namely, the TNNT3 and TNNT2 genes that regulate muscle contractions; the INS, IGF2, and DUSP8 genes associated with insulin sensitivity; and the C5NT1AL gene that is presumably related to the nucleotide metabolism process. This study is the first of its kind to find candidate genes associated with the content of all three types of nucleotide-related compounds in chicken meat using GWAS. The candidate genes identified in this study can be used for genomic selection to breed better-quality chickens in the future.

Association of single-nucleotide polymorphisms in dual specificity phosphatase 8 and insulin-like growth factor 2 genes with inosine-5'-monophosphate, inosine, and hypoxanthine contents in chickens

OBJECTIVE

This study aimed to identify the single-nucleotide polymorphisms (SNPs) in the dual-specificity phosphatase 8 (DUSP8) and insulin-like growth factor 2 (IGF2) genes and to explore their effects on inosine-5'-monophosphate (IMP), inosine, and hypoxanthine contents in Korean native chicken -red-brown line (KNC-R Line).

METHODS

A total sample of 284 (males, n = 127; females n = 157) and 230 (males, n = 106; females, n = 124) aged of 10 weeks old KNC-R line was used for genotyping of DUSP8 and IGF2 genes, respectively. One SNP (rs313443014 C>T) in DUSP8 gene and two SNPs (rs315806609A/G and rs313810945T/C) in IGF2 gene were used for genotyping by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and KASP methods, respectively. The Two-way analysis of variance of the R program was used to associate DUSP8 and IGF2 genotypes with nucleotide contents in KNC-R chickens.

RESULTS

The DUSP8 (rs313443014 C>T) was polymorphic in KNC-R line and showed three genotypes: CC, CT, and TT. The IGF2 gene (rs315806609A/G and rs313810945T/C) was also polymorphic and had three genotypes per SNP, including GG, AG, and AA for the SNP rs315806609A/G and genotypes: CC, CT, and TT for the SNP rs313810945T/C. Association resulted into a strong significant association (p<0.01) with IMP, inosine, and hypoxanthine. Moreover, the significant effect of sex (p<0.05) on nucleotide content was also observed.

CONCLUSION

The SNPs in the DUSP8 and IGF2 genes might be used as genetic markers in the selection and production of chickens with highly flavored meat.

Genome-Wide Detection and Analysis of Copy Number Variation in Anhui Indigenous and Western Commercial Pig Breeds Using Porcine 80K SNP BeadChip

Copy number variation (CNV) is an important class of genetic variations widely associated with the porcine genome, but little is known about the characteristics of CNVs in foreign and indigenous pig breeds. We performed a genome-wide comparison of CNVs between Anhui indigenous pig (AHIP) and Western commercial pig (WECP) breeds based on data from the Porcine 80K SNP BeadChip. After analysis using the PennCNV software, we detected 3863 and 7546 CNVs in the AHIP and WECP populations, respectively. We obtained 225 (loss: 178, gain: 47) and 379 (loss: 293, gain: 86) copy number variation regions (CNVRs) randomly distributed across the autosomes of the AHIP and WECP populations, accounting for 10.90% and 22.57% of the porcine autosomal genome, respectively. Functional enrichment analysis of genes in the CNVRs identified genes related to immunity (FOXJ1, FOXK2, MBL2, TNFRSF4, SIRT1, NCF1) and meat quality (DGAT1, NT5E) in the WECP population; these genes were a loss event in the WECP population. This study provides important information on CNV differences between foreign and indigenous pig breeds, making it possible to provide a reference for future improvement of these breeds and their production performance.

Targeted deletion of ecto-5'-nucleotidase results in retention of inosine monophosphate content in postmortem muscle of medaka (Oryzias latipes)

Inosine monophosphate (IMP) is an important indicator of meat freshness and contributes to its umami taste. An attractive strategy for enhancing umami is to suppress the IMP-degrading activity and increase the IMP content in the skeletal muscle through genome editing technology using the CRISPR-Cas9 system. However, the molecular mechanisms underlying IMP degradation remain unclear. We cloned two ecto-5'-nucleotidase genes, designated as ecto-5'-nucleotidase-a (nt5ea) and ecto-5'-nucleotidase-b (nt5eb), from medaka (Oryzias latipes), a vertebrate model organism. Expression analysis using embryos showed that nt5ea or nt5eb overexpression remarkably upregulated IMP degradation, and that the IMP-degrading activity was higher in Nt5ea than in Nt5eb. Furthermore, we established frame-shifted or large deletion (lacking nt5ea or nt5eb locus) mutant strains and assayed the effects of gene disruptions on the amount of IMP in skeletal muscle. The nt5ea-deficient medaka showed considerable higher levels of IMP at 48 h postmortem than did the wild-type fish. The nt5eb mutants also exhibited higher IMP contents than that in the wild types, but the increase was less than that in the nt5ea mutants. Our results demonstrated that nt5e is an important regulator of IMP levels in skeletal muscle and that its loss of function was effective in maintaining IMP content.

Science and technology of meat and meat products in Japan-Pursuit of their palatability under the influence of Washoku, traditional Japanese cuisine

This review aimed to provide an overview of meat science and technology in Japan influenced by Washoku (traditional Japanese cuisine) from the aspect of meat palatability. The tradition of umami (savory taste) research would contribute to a better understanding of the mechanism of taste improvement by aging, processing, and feeding. Paying close attention to delicate food aroma in Washoku would facilitate finding preferable Wagyu beef aroma, as well as odor substances affecting human physiological conditions. Sticking to various food textures could potentially facilitate the research of heating gel of meat and enzymatic and nonenzymatic theories for meat tenderization. High-pressure studies of meat propose a novel approach to producing low-salt products. Raw ham, Lachs-type ham, might fascinate people due to its moist texture similar to that of raw fish. Methods to season traditional fake meat using plant materials in Washoku could give a hint for improving substituted meat flavor.

Assessing genomic diversity and signatures of selection in Pinan cattle using whole-genome sequencing data

BACKGROUND

Crossbreeding is an important way to improve production beef cattle performance. Pinan cattle is a new hybrid cattle obtained from crossing Piedmontese bulls with Nanyang cows. After more than 30 years of cross-breeding, Pinan cattle show a variety of excellent characteristics, including fast growth, early onset of puberty, and good meat quality. In this study, we analyzed the genetic diversity, population structure, and genomic region under the selection of Pinan cattle based on whole-genome sequencing data of 30 Pinan cattle and 169 published cattle genomic data worldwide.  RESULTS: Estimating ancestry composition analysis showed that the composition proportions for our Pinan cattle were mainly Piedmontese and a small amount of Nanyang cattle. The analyses of nucleotide diversity and linkage disequilibrium decay indicated that the genomic diversity of Pinan cattle was higher than that of European cattle and lower than that of Chinese indigenous cattle. De-correlated composite of multiple selection signals, which combines four different statistics including θπ, CLR, F_ST, and XP-EHH, was computed to detect the signatures of selection in the Pinan cattle genome. A total of 83 genes were identified, affecting many economically important traits. Functional annotation revealed that these selected genes were related to immune (BOLA-DQA2, BOLA-DQB, LSM14A, SEC13, and NAALADL2), growth traits (CYP4A11, RPL26, and MYH10), embryo development (REV3L, NT5E, CDX2, KDM6B, and ADAMTS9), hornless traits (C1H21orf62), and climate adaptation (ANTXR2).

CONCLUSION

In this paper, we elucidated the genomic characteristics, ancestry composition, and selective signals related to important economic traits in Pinan cattle. These results will provide the basis for further genetic improvement of Pinan cattle and reference for other hybrid cattle related studies.

Ultra-rapid real-time polymerase chain reaction assay for genotyping of the NT5E gene in Japanese black beef using a mobile PCR device, PCR 1100

The concentration of inosine 5'-monophosphate (IMP) in beef is an important factor contributing to beef palatability. A previous study suggested that single nucleotide polymorphisms (SNPs) in the ecto-5'-nucleotidase (NT5E) gene strongly affect the concentration of IMP under postmortem conditions by regulating NT5E enzymatic activity in beef. Genotyping of the NT5E gene is performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or real-time PCR assay. However, these conventional laboratory assays require large installed instruments. They also involve complicated procedures and are time-consuming. Here, the PCR primers and probes for the NT5E gene (rs42508588 SNP) were designed and synthesized, and we examined the rapid genotyping of the NT5E gene using a PicoGene PCR 1100 mobile PCR device. The results showed that this system enabled rapid amplification of each allele at approximately 19.4 s per cycle, with a total run time of 13 min 36 s. This device is portable and does not require a power supply, which facilitates its use not only in specific laboratories but also in meat production farms and distribution stages of beef.

Estimates of genetic parameters for adenosine triphosphate-related compounds at different aging periods and NT5E genotypes in Japanese Black beef

Previous studies on Japanese Black beef showed that single nucleotide polymorphisms in the ecto-5'-nucleotidase (NT5E) gene affected the degradation rate of inosine 5'-monophosphate (IMP), which has contributed to the umami taste, especially between Postmortem Days 4 and 7. Therefore, this study estimated the genetic parameters of IMP and its degradation products on Postmortem Days 4 and 7 using the model with or without the NT5E genotype. The heritability estimates of IMP on Postmortem Days 4 and 7 were moderate by the model without the NT5E genotype (0.44 and 0.32, respectively). When the NT5E genotype was included in the model, the heritability of IMP on Postmortem Day 4 did not change, whereas that on Day 7 decreased from 0.32 to 0.08. The genetic correlation of IMP between Postmortem Days 4 and 7 was highly positive using the model with the NT5E genotype. Regarding the estimated breeding values (EBVs) of IMP, the ranking of EBVs among NT5E genotypes was not changed between Postmortem Days 4 and 7, when the model with the NT5E genotype was used. The study suggested that the model including NT5E genotype would allow for appropriate genetic parameter estimation and breeding value evaluation in adenosine triphosphate-related compounds (ATPRCs) under different aging periods.

Development of DNA markers for improvement of meat quality in a Japanese Black cattle population in Hyogo Prefecture

The polymorphisms associated with economic traits in livestock animals provide useful information as genetic indicators for breeding improvement. Over the last two decades, several DNA markers have been developed in Japanese Black cattle; however, the effect of these markers differs across populations due to differences in their genetic structures and backgrounds. As such, there is a need to verify the effectiveness of these markers in each population. This review summarizes the effectiveness of previously reported markers on carcass traits and the development of novel DNA markers in a Japanese Black cattle population in Hyogo Prefecture. As result of genome wide association studies and resequencing analyses, two novel significant markers associated with meat quality-related traits (beef marbling and fatty acid composition) were developed. These findings will lead to the identification of responsible genes and polymorphisms and contribute to the development of novel DNA markers for numerous traits in various cattle populations.

Evaluation of inbreeding and genetic diversity in Japanese Shorthorn cattle by pedigree analysis

The Japanese Shorthorn is a Japanese Wagyu breed maintained at a small population size. We assessed the degree of inbreeding and genetic diversity among Japanese Shorthorn cattle using pedigree analysis. We analyzed the pedigree records of registered Japanese Shorthorn born between 1980 and 2018, after evaluating the pedigree completeness. The average of the actual inbreeding coefficients increased at the same rates annually from approximately 1.5% in 1980 to 4.2% in 2018 and was higher than the expected inbreeding coefficients over time. The effective population size based on the individual coancestry rate largely decreased from 127.8 in 1980 to 82.6 in 1999, and then remained almost constant at approximately 90. Three effective numbers of ancestors decreased over time until 1995, then remained almost constant. In particular, the effective number of founder genomes (N_ge) decreased from 43.8 in 1980 to 11.9 in 2018. The index of genetic diversity based on N_ge decreased from 0.99 in 1980 to 0.96 in 2018 due to genetic drift in non‐founder generations. Changes in inbreeding and genetic diversity parameters were similar between Japanese Shorthorn and other Japanese Wagyu breeds, but the magnitude of the changes was lower in the Japanese Shorthorn.

A selection signatures study among Middle Eastern and European sheep breeds

Selection, both natural and artificial, leaves patterns on the genome during domestication of animals and leads to changes in allele frequencies among populations. Detecting genomic regions influenced by selection in livestock may assist in understanding the processes involved in genome evolution and discovering genomic regions related to traits of economic and ecological interests. In the current study, genetic diversity analyses were conducted on 34,206 quality-filtered SNP positions from 450 individuals in 15 sheep breeds, including six indigenous breeds from the Middle East, namely Iranian Balouchi, Afshari, Moghani, Qezel, Karakas and Norduz, and nine breeds from Europe, namely East Friesian Sheep, Ile de France, Mourerous, Romane, Swiss Mirror, Spaelsau, Suffolk, Comisana and Engadine Red Sheep. The SNP genotype data generated by the Illumina OvineSNP50 Genotyping BeadChip array were used in this analysis. We applied two complementary statistical analyses, F_ST (fixation index) and xp-EHH (cross-population extended haplotype homozygosity), to detect selection signatures in Middle Eastern and European sheep populations. F_ST and xp-EHH detected 629 and 256 genes indicating signatures of selection, respectively. Genomic regions identified using F_ST and xp-EHH contained the CIDEA, HHATL, MGST1, FADS1, RTL1 and DGKG genes, which were reported earlier to influence a number of economic traits. Both F_ST and xp-EHH approaches identified 60 shared genes as the signatures of selection, including four candidate genes (NT5E, ADA2, C8A and C8B) that were enriched for two significant Gene Ontology (GO) terms associated with the adenosine metabolic procedure. Knowledge about the candidate genomic regions under selective pressure in sheep breeds may facilitate identification of the underlying genes and enhance our understanding on these genes role in local adaptation.

Identification of Umami Taste in Sous-vide Beef by Chemical Analyses, Equivalent Umami Concentration, and Electronic Tongue System

Behaviour of umami compounds that are associated with non-volatile compounds on slow cooking regimes remains less explored. This study aims to assess the ability of the electronic tongue system on the umami taste from sous-vide beef semitendinosus. The identification was based on the taste-enhancing synergism between umami compounds 5’-nucleotides (IMP, GMP, AMP, inosine, and hypoxanthine) and free amino acids (glutamic and aspartic acid) using the estimation of equivalent umami concentration (EUC) and electronic tongue system. Sous-vide cooked at 60 and 70 °C for 6 and 12 h and cooked using the conventional method at 70 °C for 30 min (as control) were compared. The temperature had a significant effect on 5’-nucleotides, but aspartic and glutamic acid were not influenced by any treatments applied. Sous-vide cooked at 60 °C tended to have higher inosine and hypoxanthine. Meanwhile, desirable 5’-nucleotides IMP, AMP, and GMP were more intensified at the temperature of 70 °C. The principal component analysis predicted a good correlation between EUC and the electronic tongue, with sous-vide at 70 °C for 12 h presenting the most umami. Therefore, the electronic tongue system is a useful tool in food processing, particularly in determining complex sensory properties such as umami, which cannot be evaluated objectively.

The NT5E gene variant strongly affects the degradation rate of inosine 5'-monophosphate under postmortem conditions in Japanese Black beef

Inosine 5'-monophosphate (IMP) contributes to the umami taste in Japanese Black beef. In a previous study, it was suggested that single nucleotide polymorphisms (SNPs) in the ecto-5'-nucleotidase (NT5E) gene affect the concentration of IMP under postmortem conditions by regulating NT5E enzymatic activity in Japanese Black beef. The present study showed that the degradation rate of IMP in Japanese Black beef was significantly different among NT5E genotypes in the middle stage of postmortem, indicating a significant difference in the concentrations of IMP and its degradation products among NT5E genotypes. In addition, no significant difference was observed among NT5E genotypes in the concentrations of IMP precursors or other taste-active compounds. These results indicate the significant effect of the interaction between the NT5E genotype and the aging period on the degradation rate of IMP in beef.

Comparison of liver transcriptome from high- and low-intramuscular fat Chaohu ducks provided additional candidate genes for lipid selection

The meat quality of ducks is closely related to the intramuscular fat (IMF) content. This study explored the candidate regulatory genes of IMF formation and lipid deposition in Chaohu ducks. The IMF of breast muscle in 100 ducks was determined and statistically analysed by normal distribution test. Duck liver samples with high IMF (CH, n = 3) and low IMF (CL, n = 3) were selected for transcriptome analysis by RNA sequencing (RNA-Seq). The IMF was in accordance with normal distribution (T = 0.001, P = 0.999). The IMF from two tails of the normal distribution was significantly different with 2.9983% ± 0.3296% in the CH group and 1.1960% ± 0.1481% in the CL group (P < 0.0001). RNA-Seq revealed 147 differentially expressed genes, including 78 up-regulated and 69 down-regulated genes in both groups. Validation by qRT-PCR was in agreement with RNA-Seq (R ² = 0.838). Gene ontology analysis revealed that organophosphate catabolism, oxidation-reduction process, cellular lipid catabolism, lipid transport, lipid localisation, lipid biosynthesis and cellular lipid catabolism were involved in lipid metabolism. Meanwhile, Kyoto Encyclopedia of Genes and Genomes pathway analysis suggested that steroid hormone biosynthesis, ovarian steroidogenesis, alpha-linolenic acid metabolism, glycosylphosphatidylinositol anchor biosynthesis and linoleic acid metabolism were involved in lipid deposition, wherein the genes COMT, NT5E, PDE4D, PLA2G4F, A-FABP, ADRA2A, HSD17B2, PPP1R3C, PPP1R3B and NR0B2 were involved in lipid deposition. This study provided insights into the molecular mechanism for regulating lipid metabolism and identified candidate genes for selecting markers to control IMF formation in Chaohu ducks.

Genome-wide association studies identified variants for taurine concentration in Japanese Black beef

We performed genome-wide association studies (GWAS) using the BovineSNP50 array to detect significant single nucleotide polymorphisms (SNPs) that may affect the concentration of 22 free amino acids and three peptides in Japanese Black beef cattle. A total of 574 Japanese Black cattle and 40,657 SNPs from the array were used for this study. Genome-wide significant SNPs were detected for β-alanine (three SNPs on chromosomes 22 and 29) and taurine (26 SNPs on chromosome 22). Importantly, the top two SNPs for taurine were highly significant (p = 6.2 × 10^-21 ), and the frequency of the increase-concentration allele (Q) for taurine was found to be 0.73. The Q allele frequency of this population was similar to that of the other unrelated Japanese Black cattle, but different from that of the other breeds. In addition, the significant SNPs were not associated with carcass traits or fatty acid compositions. Interestingly, the top three of the four most significant SNPs for taurine were located near solute carrier family 6, member 6 (SLC6A6), which is a membrane transporter for taurine. We also found two associated variants in the 5'-upstream region of SLC6A6; however, they were less significantly associated than the SNPs from the BovineSNP50 array.