Khan Khalid, Suhail Syed Muhammad, Khan Rajwali, Ahmed Ijaz, Khan Farhan Anwar, Khan Muhammad Jawad
Department of Livestock Management, Breeding and Genetics, The University of Agriculture Peshawar, Peshawar, 15130, Pakistan.
College of Veterinary Science, The University of Agriculture Peshawar, Peshawar, 15130, Pakistan.
Trop Anim Health Prod. 2023 Feb 21;55(2):94. doi: 10.1007/s11250-023-03511-9.
The aim of this study was to find out the genetic polymorphism in β-casein gene CSN2 in Azi-Kheli buffaloes found in district Swat. Blood samples from 250 buffaloes were collected and processed in lab for sequencing to see the genetic polymorphism in CSN2 gene on 67 position of exon7. The β-casein is a milk second abundant protein having some variants, wherein A1 and A2 are the most common. After performing sequence analysis, it was found that Azi-Kheli buffaloes were homozygous for only A2 type variant. The amino acid change (proline to histadine) on 67 position of exon 7 was not found; however, three other novel SNPs at loci g.20545A > G, g.20570G > A, and g.20693C > A were identified in the study. Amino acid change due to SNPs were found as SNP1, valine > proline; SNP2, leucin > phenylalanine; and SNP3, threonine > valine. Allelic and genotypic frequencies' analysis exhibited that all three SNPs were following the Hardy-Weinberg equilibrium (HWE: P < 0.05). All the three SNPs showed medium PIC value and gene heterozygosity. The SNPs located on different position of exon 7 of CSN2 gene exhibited associations with some of the performance traits and milk composition. Higher daily milk yield of 9.86 ± 0.43 L and the peak milk yield of 13.80 ± 0.60 L were found in response to SNP3 followed by SNP2 and SNP1. The percentage of milk fat and protein was found significantly higher (P ≤ 0.05) in relation to SNP3 followed by SNP2 and SNP1 given as 7.88 ± 0.41, 7.48 ± 0.33, and 7.15 ± 0.48 for fat% and 4.00 ± 0.15, 3.73 ± 0.10 and 3.40 ± 0.10 for protein%. It was concluded that Azi-Kheli buffalo milk contains A2 genetic variant along with other useful novel variants indicating quality milk for human health. Genotypes of SNP3 should be given preference in selection both in indices and nucleotide polymorphism.
本研究的目的是找出斯瓦特地区发现的阿齐-凯利水牛β-酪蛋白基因CSN2中的基因多态性。采集了250头水牛的血样，并在实验室进行处理以进行测序，以查看外显子7第67位CSN2基因的基因多态性。β-酪蛋白是牛奶中含量第二丰富的蛋白质，有一些变体，其中A1和A2最为常见。进行序列分析后发现，阿齐-凯利水牛仅对A2型变体呈纯合状态。未在外显子7第67位发现氨基酸变化（脯氨酸变为组氨酸）；然而，在本研究中鉴定出了位于位点g.20545A>G、g.20570G>A和g.20693C>A的另外三个新的单核苷酸多态性（SNP）。发现SNP导致的氨基酸变化为：SNP1，缬氨酸>脯氨酸；SNP2，亮氨酸>苯丙氨酸；SNP3，苏氨酸>缬氨酸。等位基因和基因型频率分析表明，所有三个SNP均符合哈迪-温伯格平衡（HWE：P<0.05）。所有三个SNP均显示出中等的多态信息含量（PIC）值和基因杂合度。位于CSN2基因外显子7不同位置的SNP与一些生产性能性状和牛奶成分存在关联。响应SNP3时发现较高的日产奶量（9.86±0.43升）和产奶峰值（13.80±0.60升），其次是SNP2和SNP1。发现相对于SNP3，牛奶脂肪和蛋白质的百分比显著更高（P≤0.05），其次是SNP2和SNP1，脂肪百分比分别为7.88±0.41、7.48±0.33和7.15±0.48，蛋白质百分比分别为4.00±0.15、3.73±0.10和3.40±0.10。得出的结论是，阿齐-凯利水牛奶含有A2基因变体以及其他有用的新变体，表明其对人类健康有益的优质牛奶。在选择指数和核苷酸多态性时，应优先考虑SNP3的基因型。
