School of Animal & Veterinary Sciences, University of Adelaide, Roseworthy Campus, Roseworthy, SA, 5371, Australia.
Mamm Genome. 2012 Jun;23(5-6):378-86. doi: 10.1007/s00335-012-9396-0. Epub 2012 Mar 24.
Beef with yellow fat is considered undesirable by consumers in most European and Asian markets. β-Carotene is the major carotenoid deposited in the adipose tissue and milk fat of cattle (Bos taurus), which can result in the yellowness. The effects of retinal short-chain dehydrogenase reductase (RDHE2) and β, β-carotene 9',10-dioxygenase (BCO2) were considered jointly as major candidate genes for causing the yellow fat colour, based on their genomic locations in the fat colour quantitative trait loci (QTL) and their roles in the metabolism of β-carotene. In a secondary pathway, BCO2 cleaves β-carotene into retinoic acid, the most potent form of vitamin A. RDHE2 converts trans-retinol to trans-retinal, a less active form of vitamin A. We evaluated the effects of two amino acid variants of the RDHE2 gene (V6A and V33A) along with a mutation in the BCO2 gene that results in a stop codon (W80X) in seven cattle populations. The RDHE2 V6A genotype affected several fat colour traits but the size of the effect varied in the populations studied. The genotype effect of the RDHE2 V33A variant was observed only in New Zealand samples of unknown breed. In general, the individual effects of RDHE2 V6A and V33A SNPs genotypes were greater in the random New Zealand samples than in samples from pedigreed Jersey-Limousin backcross progeny, accounting for 8-17 % of the variance in one population. Epistasis between the BCO2 W80X and RDHE2 variants was observed, and in some populations this explained more of the variation than the effects of the individual RDHE2 variants.
黄色脂肪的牛肉在大多数欧洲和亚洲市场都不受消费者欢迎。β-胡萝卜素是牛（Bos taurus）脂肪组织和乳脂中主要沉积的类胡萝卜素，这会导致脂肪变黄。基于视网膜短链脱氢酶还原酶（RDHE2）和β，β-胡萝卜素 9'，10-加氧酶（BCO2）在脂肪颜色数量性状基因座（QTL）中的基因组位置及其在β-胡萝卜素代谢中的作用，它们被认为是导致黄色脂肪颜色的主要候选基因。在次要途径中，BCO2 将β-胡萝卜素切割成视黄醛，这是维生素 A 的最有效形式。RDHE2 将反式视黄醇转化为视黄醛，这是一种活性较低的维生素 A 形式。我们评估了 RDHE2 基因的两个氨基酸变异（V6A 和 V33A）以及 BCO2 基因的突变（导致 W80X 终止密码子）对七个牛种群的影响。RDHE2 V6A 基因型影响了几种脂肪颜色性状，但在研究的种群中效应大小有所不同。仅在新西兰来源不明的品种样本中观察到 RDHE2 V33A 变体的基因型效应。一般来说，RDHE2 V6A 和 V33A SNP 基因型的个体效应在随机的新西兰样本中大于从有 pedigree Jersey-Limousin 回交后代的样本，在一个种群中占 8-17%的方差。还观察到了 BCO2 W80X 和 RDHE2 变异体之间的上位性，在某些群体中，这种上位性比单个 RDHE2 变异体的效应解释了更多的变异。
