白尾鹿（Odocoileus virginianus）中两个 MHC II 基因（DOB、DRB）的特征。

Characterization of two MHC II genes (DOB, DRB) in white-tailed deer (Odocoileus virginianus).

机构信息

School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL, 36849, USA.

Department of Biological Sciences, Auburn University, Auburn, AL, 36849, USA.

出版信息

BMC Genet. 2020 Jul 29;21(1):83. doi: 10.1186/s12863-020-00889-5.

DOI:10.1186/s12863-020-00889-5

PMID:32727360

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC7392685/

Abstract

BACKGROUND

The major histocompatibility complex (MHC) is responsible for detecting and addressing foreign pathogens inside the body. While the general structure of MHC genes is relatively well conserved among mammalian species, it is notably different among ruminants due to a chromosomal inversion that splits MHC type II genes into two subregions (IIa, IIb). Recombination rates are reportedly high between these subregions, and a lack of linkage has been documented in domestic ruminants. However, no study has yet examined the degree of linkage between these subregions in a wild ruminant. The white-tailed deer (Odocoileus virginianus), a popular ruminant of the Cervidae family, is habitually plagued by pathogens in its natural environment (e.g. Haemonchus contortus, Elaeophora). Due to the association between MHC haplotypes and disease susceptibility, a deeper understanding of MHC polymorphism and linkage between MHC genes can further aid in this species' successful management. We sequenced MHC-DRB exon 2 (IIa) and MHC-DOB exon 2 (IIb) on the MiSeq platform from an enclosed white-tailed deer population located in Alabama.

RESULTS

We identified 12 new MHC-DRB alleles, and resampled 7 alleles, which along with other published alleles brings the total number of documented alleles in white-tailed deer to 30 for MHC-DRB exon 2. The first examination of MHC-DOB in white-tailed deer found significantly less polymorphism (11 alleles), as was expected of a non-classical MHC gene. While MHC-DRB was found to be under positive, diversifying selection, MHC-DOB was found to be under purifying selection for white-tailed deer. We found no significant linkage disequilibrium between MHC-DRB and MHC-DOB, suggesting that these loci are unlikely to be closely linked.

CONCLUSIONS

Overall, this study identified 12 new MHC-DRB exon 2 alleles and characterized a new, non-classical, MHC II gene (MHC-DOB) for white-tailed deer. We also found a lack of significant linkage between these two loci, which supports previous findings of a chromosomal inversion within the MHC type II gene region in ruminants, and suggests that white-tailed deer may have a recombination hotspot between these MHC regions similar to that found for Bos taurus.

摘要

背景

主要组织相容性复合体 (MHC) 负责检测和应对体内的外来病原体。虽然 MHC 基因的一般结构在哺乳动物物种中相对保守，但由于染色体倒位，反刍动物的 MHC 类型 II 基因分裂成两个亚区 (IIa、IIb)，其结构明显不同。据报道，这些亚区之间的重组率很高，并且在国内反刍动物中已经记录到缺乏连锁。然而，尚无研究检查野生反刍动物中这些亚区之间的连锁程度。白尾鹿（Odocoileus virginianus）是鹿科家族中一种受欢迎的反刍动物，其在自然环境中经常受到病原体的困扰（例如 Haemonchus contortus、Elaeophora）。由于 MHC 单倍型与疾病易感性之间的关联，深入了解 MHC 多态性和 MHC 基因之间的连锁关系可以进一步帮助该物种的成功管理。我们在阿拉巴马州的一个封闭的白尾鹿种群中使用 MiSeq 平台对 MHC-DRB 外显子 2（IIa）和 MHC-DOB 外显子 2（IIb）进行了测序。

结果

我们鉴定了 12 个新的 MHC-DRB 等位基因，并重新采样了 7 个等位基因，加上其他已发表的等位基因，使白尾鹿 MHC-DRB 外显子 2 的记录等位基因总数达到 30 个。首次对白尾鹿 MHC-DOB 的研究发现，其多态性显著较低（11 个等位基因），这是对非经典 MHC 基因的预期。尽管 MHC-DRB 被发现处于正选择下，具有多样化选择，但 MHC-DOB 被发现对白尾鹿处于纯化选择之下。我们没有发现 MHC-DRB 和 MHC-DOB 之间存在显著的连锁不平衡，这表明这些位点不太可能紧密连锁。

结论

总的来说，这项研究鉴定了 12 个新的 MHC-DRB 外显子 2 等位基因，并对白尾鹿的一个新的非经典 MHC II 基因（MHC-DOB）进行了特征描述。我们还发现这两个位点之间缺乏显著的连锁，这支持了先前在反刍动物 MHC 类型 II 基因区域内发现的染色体倒位的发现，并表明白尾鹿在这些 MHC 区域之间可能存在与牛相似的重组热点。