Exploring genotype-phenotype relationships of the CRABP2 gene on growth traits in beef cattle.

Cellular retinoic acid binding protein 2 (CRABP2) is essential to myoblast differentiation. However, there was no report about the function of CRABP2 gene in cattle. This study explored the association of CRABP2 gene polymorphisms with growth traits in cattle breeds by several methods, such as DNA sequencing, PCR, PCR-RFLP and forced PCR-RFLP. Two sequence variants were determined. There were 621 individuals in six cattle breeds from China for the experiment, and three breeds were used to test validation of polymorphisms and extent of linkage disequilibrium (LD). The results showed that both SNPs (SNP1, g.2458 G > T, SNP2, g.3878 G > A) were in intron1. Two SNPs were in low linkage disequilibrium. Association analysis suggested that SNP1 had the significant difference on growth traits with body height, height at hip cross and body slanting length (P < .05), while SNP2 showed a significant difference in growth traits with body height, height at hip cross and body slanting length(P < .05). The results of this investigation displayed that the CRABP2 gene is an available candidate gene and may be used for breed selection and conservation.

DNA methylation status of CRABP2 promoter down-regulates its expression.

As an important epigenetic modification DNA methylation is catalyzed by DNA methylation transferases (DNMTs) and occurs mainly in CpG islands. DNA methylation plays an important role in regulates gene expression, cell differentiation, genetic imprinting and tumor therapy. Retinoic acid-binding proteins (RAC) is vital for the absorption, transport, metabolism and maintenance of homeostasis of retinoic acid, which in turn regulates the differentiation and proliferation of cells by regulating the transcription of many target genes, therefore, these proteins influence differentiation and proliferation of adipocytes and muscle fibroblasts. Thus, cellular retinoic acid binding protein 2 (CRABP2) may be a candidate gene which affects beef quality, yield and fat deposition. The aim of this study was to evaluate the expression and the methylation pattern on the differentially methylated region (DMR) of the promoter of CRABP2. The DNA methylation pattern was tested by bisulfite sequencing polymerase chain reaction (BSP), the quantitative real-time PCR (qPCR) was used to analysis the expression of CRABP2 gene. The results showed that the DNA methylation level was higher in purebred cattle breed than that in hybrid cattle breeds which was negative correlation with the expression of the gen. These results indicate that the methylation status of the CRABP2 DMR can regulate mRNA expression. What's more, there are different methylation and expression patterns in different breeds and tissues which may influence the phenotype, and the results may be a useful parameter to investigate the function of CRABP2 in muscle and fat developmental in Chinese cattle.