Lewerentz Frida, Vanhala Tytti K, Johansen Lene Buhelt, Paulsson Marie, Glantz Maria, de Koning Dirk-Jan
Department of Process and Life Science Engineering, Division of Food and Pharma, Lund University, SE-221 00 Lund, Sweden.
Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.
JDS Commun. 2024 Feb 29;5(4):299-304. doi: 10.3168/jdsc.2023-0412. eCollection 2024 Jul.
Impaired rennet coagulation properties in milk could lead to prolonged processing times and production losses. Heritability for milk coagulation has previously been estimated to be 0.28 to 0.45, indicating that genetic selection can be used to manipulate this trait. The CN proteins are expressed by the genes , and and are located on bovine chromosome 6. To better understand the effect of genetic variation in the CN genes on milk coagulation, blood and milk samples from 30 Swedish Red Dairy Cattle (RDC) with divergent coagulation properties were investigated. DNA from the 30 cows was sequenced for the CN genes to determine the theoretical AA sequence and to look for genetic variation in the untranslated regions. The aim is to confirm the protein genetic variants previously reported, while searching for additional genetic variation in the CN genes of 30 RDC. We observed genetic variation in 116 SNPs in the known CN genes where 10% of the SNPs are exon variants and the remaining 90% are intron variants. A total of 2.5% of the SNPs are found in the 5'- or 3'-untranslated region (UTR) regions of the exons; 2% are synonymous variants and 6% are missense variants that concurred with the known protein variants for , and . Furthermore, 6% of the SNPs are splice polypyrimidine tract intron variants. The 2 genetic variants in the 5'- and 3'-UTR in and are found with protein variants and . Because both UTR variants are associated with gain and loss of micro RNA and transcription factors, this could explain differences in expression of the genetic protein variants. Preliminary chi-squared analysis and comparison with previous GWAS studies showed potential connections between the identified SNPs and coagulation properties of milk. By advancing the knowledge of the connection between the DNA sequence and the functional properties of the CN proteins, we hope to learn more about the cheese coagulation properties of milk from RDC.
牛奶中凝乳酶凝固特性受损可能导致加工时间延长和生产损失。先前估计牛奶凝固的遗传力为0.28至0.45，这表明可以通过基因选择来控制这一性状。酪蛋白（CN）由基因、和表达，位于牛的6号染色体上。为了更好地了解CN基因的遗传变异对牛奶凝固的影响，对30头具有不同凝固特性的瑞典红奶牛（RDC）的血液和牛奶样本进行了研究。对这30头奶牛的DNA进行CN基因测序，以确定理论氨基酸序列，并寻找非翻译区的遗传变异。目的是确认先前报道的蛋白质遗传变异，同时在30头RDC的CN基因中寻找其他遗传变异。我们在已知的CN基因中观察到116个单核苷酸多态性（SNP）的遗传变异，其中10%的SNP是外显子变异，其余90%是内含子变异。总共2.5%的SNP存在于外显子的5'或3'非翻译区（UTR）；2%是同义变异，6%是错义变异，与已知的、和的蛋白质变异一致。此外，6%的SNP是剪接多嘧啶 tract内含子变异。在和的5'和3'UTR中的2个遗传变异与蛋白质变异和有关。由于这两个UTR变异都与微小RNA和转录因子的增减有关，这可以解释遗传蛋白质变异表达的差异。初步的卡方分析以及与先前全基因组关联研究（GWAS）的比较表明，所鉴定的SNP与牛奶的凝固特性之间存在潜在联系。通过增进对DNA序列与CN蛋白质功能特性之间联系的了解，我们希望更多地了解RDC牛奶的奶酪凝固特性。
