揭示基因组近交和选择模式的 Homozygosity 运行特征在本土萨希瓦尔牛中。

Characterization of runs of Homozygosity revealed genomic inbreeding and patterns of selection in indigenous sahiwal cattle.

机构信息

Livestock Research Station, Garividi, Sri Venkateswara Veterinary University, Tirupati, Andhra Pradesh State, India.

Animal Husbandry Department, Kolkata, West Bengal State, India.

出版信息

J Appl Genet. 2024 Feb;65(1):167-180. doi: 10.1007/s13353-023-00816-1. Epub 2023 Dec 18.

Abstract

Runs of homozygosity (ROH) are contiguous genomic regions, homozygous across all sites which arise in an individual due to the parents transmitting identical haplotypes to their offspring. The genetic improvement program of Sahiwal cattle after decades of selection needs re-assessment of breeding strategy and population phenomena. Hence, the present study was carried out to optimize input parameters in PLINK for ROH estimates, to explore ROH islands and assessment of pedigree and genome-based inbreeding in Sahiwal cattle. The sliding window approach with parameters standardized to define ROH for the specific population under study was used for the identification of runs. The optimum maximum gap, density, window-snp and window-threshold were 250 Kb, 120 Kb/SNP, 10, 0.05 respectively and ROH patterns were also characterized. ROH islands were defined as the short homozygous genomic regions shared by a large proportion of individuals in a population, containing significantly higher occurrences of ROH than the population specific threshold level. These were identified using the -homozyg-group function of the PLINK v1.9 program. Our results indicated that the Islands of ROH harbor a few candidate genes, ACAD11, RFX4, BANP, UBA5 that are associated with major economic traits. The average F (Pedigree based inbreeding coefficient), F (Genomic inbreeding coefficient), F (Inbreeding estimated as the ratio of observed and expected homozygous genotypes), F (Inbreeding estimated on genomic relationship method) and F (Inbreeding estimated from the diagonal of a GRM with allele frequencies near to 0.5) were 0.009, 0.091, 0.035, -0.104 and -0.009, respectively. Our study revealed the optimum parameter setting in PLINK viz. maximal gaps between two SNPs, minimal density of SNPs in a segment (in kb/SNP) and scanning window size to identify ROH segments, which will enable ROH estimation more efficient and comparable across various SNP genotyping-based studies. The result further emphasized the significant role of genomics in unraveling population diversity, selection signatures and inbreeding in the ongoing Sahiwal breed improvement programs.

摘要

纯合子区域(ROH)是连续的基因组区域,在个体中所有位点都是纯合的,这是由于父母将相同的单倍型传递给后代。在经过几十年的选择后,萨希瓦尔牛的遗传改良计划需要重新评估其育种策略和群体现象。因此,本研究旨在优化 PLINK 中用于 ROH 估计的输入参数,探索 ROH 岛,并评估萨希瓦尔牛的系谱和基于基因组的近亲繁殖。使用标准化参数的滑动窗口方法来定义特定研究人群中的 ROH,用于识别运行。最佳最大间隙、密度、窗口 SNP 和窗口阈值分别为 250 Kb、120 Kb/SNP、10、0.05,同时还对 ROH 模式进行了特征描述。ROH 岛被定义为短的纯合基因组区域,这些区域在一个群体中的很大一部分个体中共享,包含明显高于群体特定阈值水平的 ROH 发生频率。这些是使用 PLINK v1.9 程序的 -homozyg-group 函数来识别的。我们的结果表明,ROH 岛上存在一些候选基因,如 ACAD11、RFX4、BANP、UBA5,它们与主要经济性状有关。平均 F(基于系谱的近交系数)、F(基于基因组的近交系数)、F(根据观测到的和预期的纯合基因型计算的近交系数)、F(基于基因组关系方法估计的近交系数)和 F(从 GRM 对角线估计的近交系数,等位基因频率接近 0.5)分别为 0.009、0.091、0.035、-0.104 和-0.009。我们的研究揭示了 PLINK 中的最佳参数设置,即两个 SNP 之间的最大间隙、片段中 SNP 的最小密度(以 kb/SNP 表示)和扫描窗口大小,以识别 ROH 片段,这将使 ROH 估计在各种 SNP 基因分型研究中更加高效和可比。结果进一步强调了基因组学在揭示群体多样性、选择特征和正在进行的萨希瓦尔牛品种改良计划中的近交方面的重要作用。

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