Consiglio per la ricerca in agricoltura e l'analisi dell'economia agraria (CREA) - Centro di ricerca Zootecnia e Acquacoltura, 00015Monterotondo, Rome, Italy.
Associazione Nazionale Allevatori Bovini di razza Pezzata Rossa Italiana, 33100Udine, Italy.
J Dairy Res. 2021 Nov;88(4):368-373. doi: 10.1017/S0022029921000832. Epub 2021 Dec 13.
Cluster of differentiation 4 (CD4) is the accessory protein non-covalently bound to the T cell receptor that recognizes an invariant region of MHC class II on antigen presenting cells. Its cytoplasmic tail, physically associated with a protein tyrosine kinase, is important in the activation of helper/inducer T lymphocytes. In Bos taurus, CD4 gene is located on chromosome 5 from which two isoforms are transcribed, with a different number of amino acids due to splicing of exon 7 and variation in the reading frame. The aim of this study was to investigate the sequence of the entire CD4 gene in Simmental sires to evaluate the effects of genomic variants on the indexes of the bulls for milk, fat and protein yields, as well as somatic cell score. The associations among genomic variants and indexes were analysed using the Allele and GLM procedures of SAS 9.4. The analysis indicated that only four of the thirty-one identified SNPs influenced the considered traits. Identified variants insist on coding zones and intronic sequences, where we revealed the presence of sites for transcription factors. To evaluate the existence of haplotypic effects, combinations among the four genomic variants (SNP 3, SNP 8, SNP 11 and SNP 19) were investigated. Six different haplotypic alleles were identified, but only four of them were frequent enough to allow for an evaluation of any haplotypic effect (at least six copies in the examined sample): Hap1, Hap2, Hap3 and Hap6. The analysis of associations between the selected haplotypes in the CD4 gene with milk related indexes showed that bulls with Hap2 (T-A-C-C) had better indexes for milk and protein yields (P < 0.05), whereas the presence of the Hap1 haplotype (A-G-A-T) caused a significant decrease of the index for protein yield (P < 0.05). Frequencies of the two alleles Hap1 and Hap2 (9 and 36% respectively) make them of interest for their possible inclusion in breeding schemes and support the hypothesis of considering this gene as a candidate for the improvement of milk-related traits in the Simmental breed.
CD4 是一种非共价结合在 T 细胞受体上的辅助蛋白，可识别抗原呈递细胞上 MHC Ⅱ类的不变区域。其细胞质尾巴与一种蛋白酪氨酸激酶物理相关，在辅助/诱导性 T 淋巴细胞的激活中很重要。在牛属中，CD4 基因位于 5 号染色体上，该基因转录出两种同工型，由于外显子 7 的剪接和阅读框的变化，导致氨基酸数量不同。本研究旨在研究西门塔尔公牛 CD4 基因的全长序列，以评估基因组变异对公牛产奶、产脂和产蛋白量以及体细胞评分等指标的影响。使用 SAS 9.4 的 Allele 和 GLM 程序分析了基因组变异与指标之间的关系。分析表明，在所鉴定的 31 个 SNP 中，只有 4 个影响了所考虑的性状。鉴定出的变体坚持编码区和内含子序列，在这些序列中，我们发现了转录因子的存在位点。为了评估单倍型效应的存在，我们研究了四个基因组变异（SNP3、SNP8、SNP11 和 SNP19）之间的组合。鉴定出了 6 种不同的单倍型等位基因，但只有其中 4 种足够频繁，能够评估任何单倍型效应（在被检查的样本中至少有 6 个拷贝）：Hap1、Hap2、Hap3 和 Hap6。CD4 基因中选择的单倍型与产奶相关指标之间的关联分析表明，携带 Hap2（T-A-C-C）的公牛具有更好的产奶和产蛋白量指数（P < 0.05），而 Hap1 单倍型（A-G-A-T）的存在导致产蛋白量指数显著下降（P < 0.05）。两个等位基因 Hap1 和 Hap2 的频率（分别为 9%和 36%）使它们成为关注的对象，因为它们可能被纳入育种计划，并支持将该基因作为提高西门塔尔品种产奶相关性状的候选基因的假设。
