Genetic Variation in FABP4 and Evaluation of Its Effects on Beef Cattle Fat Content

FABP4 is a protein primarily expressed in adipocytes and macrophages that plays a key role in fatty acid trafficking and lipid hydrolysis. FABP4 gene polymorphisms have been associated with meat quality traits in cattle, mostly in Asian breeds under feedlot conditions. The objectives of this work were to characterize FABP4 genetic variation in several worldwide cattle breeds and evaluate possible genotype effects on fat content in a pasture-fed crossbred (Angus-Hereford-Limousin) population. We re-sequenced 43 unrelated animals from nine cattle breeds (Angus, Brahman, Creole, Hereford, Holstein, Limousin, Nelore, Shorthorn, and Wagyu) and obtained 22 single nucleotide polymorphisms (SNPs) over 3,164 bp, including four novel polymorphisms. Haplotypes and linkage disequilibrium analyses showed a high variability. Five SNPs were selected to perform validation and association studies in our crossbred population. Four SNPs showed well-balanced allele frequencies (minor frequency > 0.159), and three showed no significant deviations from Hardy-Weinberg proportions. SNPs showed significant effects on backfat thickness and fatty acid composition (P脂肪酸结合蛋白4（FABP4）是一种主要在脂肪细胞与巨噬细胞中表达的蛋白质，在脂肪酸转运与脂质水解过程中发挥关键作用。FABP4基因多态性与牛的肉质性状存在关联，此类研究多集中于舍饲条件下的亚洲肉牛品种。本研究旨在对全球多个肉牛品种中的FABP4遗传变异进行系统表征，并评估放牧饲养的安格斯-赫里福德-利木赞杂交群体中，不同基因型对脂肪含量的潜在影响。我们对9个肉牛品种（安格斯、婆罗门、克里奥尔、赫里福德、荷斯坦、利木赞、内洛尔、短角牛及和牛）的43头无亲缘关系个体进行了重测序，在长度为3164 bp的序列区段内共获得22个单核苷酸多态性（single nucleotide polymorphisms，SNPs）位点，其中包含4个新发现的多态位点。单倍型与连锁不平衡分析结果显示该区域具有较高的遗传变异水平。我们选取其中5个SNPs用于该杂交群体的验证与关联分析。其中4个SNPs的等位基因频率分布较为均衡（次要等位基因频率>0.159），另有3个SNPs的基因型分布未出现显著偏离哈迪-温伯格平衡比例（Hardy-Weinberg proportions）的情况。各SNPs位点对背膘厚度及脂肪酸组成均具有显著影响（P