The armadillo (Dasypus novemcinctus): a Witness but not a Functional example for the emergence of the Butyrophilin 3/Vγ9Vδ2 system in Placental Mammals
The armadillo (Dasypus novemcinctus): a Witness but not a Functional example for the emergence of the Butyrophilin 3/Vγ9Vδ2 system in Placental Mammals
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DOI：
10.3389/fimmu.2018.00265
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发表时间：
2018-02-23
影响因子：
7.3
通讯作者：
Herrmann, Thomas
中科院分区：
文献类型：
--
作者：
Fichtner, Alina Suzann;Karunakaran, Mohindar Murugesh;Herrmann, Thomas
1 - 5%的人血液T细胞是V γ 9V δ 2 T细胞，其T细胞受体（TCR）含有TRGV 9/TRGJP重排和包含V δ 2链的TRDV 2。它们以亲丁酸蛋白3（BTN3）依赖性方式对磷酸化抗原（PAg）如异戊烯基焦磷酸或（E）-4-羟基-3-甲基-丁-2-烯基-焦磷酸（HMBPP）作出应答，并可能有助于控制分枝杆菌感染。这些细胞被认为仅限于灵长类动物，但我们通过对基因组数据库的分析表明，TRGV 9，TRDV 2和BTN3基因与胎盘哺乳动物共同进化并出现。此外，我们将羊驼（Vicugna pacos）鉴定为具有典型V γ 9V δ 2 TCR重排的物种，并且目前旨在直接鉴定V γ 9V δ 2 T细胞和BTN3。研究这种共同进化的其他候选者是海豚（Tursiops truncatus）和九带犰狳（Dasypus novemcinctus），它们的基因组序列编码TRGV 9、TRDV 2和BTN3细胞外部分的开放阅读框架。海豚已显示表达V γ 9样和V δ 2样TCR链，并具有与人BTN3A3同源的预测的BTN3样基因。另一个候选者，犰狳，是医学上的兴趣，因为它作为麻风分枝杆菌的天然水库。在这项研究中，我们分析了犰狳基因组，并发现了多个非功能BTN3基因的证据，包括与人类、羊驼和海豚BTN3A3基因座的组织非常相似的基因组背景。然而，在犰狳cDNA中没有检测到BTN3转录本。此外，通过PCR鉴定功能性TRGV 9/TRGJP重排的尝试失败。与此相反，完整的TRDV 2基因片段优先与TRDJ 4同源物重排克隆和共表达的人V γ 9-链在鼠杂交瘤细胞。这些细胞可以被固定化的抗小鼠CD3抗体刺激，但不能被人RAJI-RT1B1细胞和HMBPP刺激。到目前为止，TRGV 9重排和BTN3表达的缺乏使得犰狳不太可能成为PAG反应性V γ 9V δ 2 T细胞的候选物种。这与假定的三种基因的共同进化一致，其中V γ 9V δ 2 TCR的出现与功能性BTN3分子一致。
1-5% of human blood T cells are V gamma 9V delta 2 T cells whose T cell receptor (TCR) contain a TRGV9/TRGJP rearrangement and a TRDV2 comprising V delta 2-chain. They respond to phosphoantigens (PAgs) like isopentenyl pyrophosphate or (E)-4-hydroxy-3-methyl-but-2-enyl-pyrophosphate (HMBPP) in a butyrophilin 3 (BTN3)-dependent manner and may contribute to the control of mycobacterial infections. These cells were thought to be restricted to primates, but we demonstrated by analysis of genomic databases that TRGV9, TRDV2, and BTN3 genes coevolved and emerged together with placental mammals. Furthermore, we identified alpaca (Vicugna pacos) as species with typical V gamma 9V delta 2 TCR rearrangements and currently aim to directly identify V gamma 9V delta 2 T cells and BTN3. Other candidates to study this coevolution are the bottlenose dolphin (Tursiops truncatus) and the nine-banded armadillo (Dasypus novemcinctus) with genomic sequences encoding open reading frames for TRGV9, TRDV2, and the extracellular part of BTN3. Dolphins have been shown to express V gamma 9-and V delta 2-like TCR chains and possess a predicted BTN3-like gene homologous to human BTN3A3. The other candidate, the armadillo, is of medical interest since it serves as a natural reservoir for Mycobacterium leprae. In this study, we analyzed the armadillo genome and found evidence for multiple non-functional BTN3 genes including genomic context which closely resembles the organization of the human, alpaca, and dolphin BTN3A3 loci. However, no BTN3 transcript could be detected in armadillo cDNA. Additionally, attempts to identify a functional TRGV9/TRGJP rearrangement via PCR failed. In contrast, complete TRDV2 gene segments preferentially rearranged with a TRDJ4 homolog were cloned and co-expressed with a human V gamma 9-chain in murine hybridoma cells. These cells could be stimulated by immobilized anti-mouse CD3 antibody but not with human RAJI-RT1Bl cells and HMBPP. So far, the lack of expression of TRGV9 rearrangements and BTN3 renders the armadillo an unlikely candidate species for PAg-reactive V gamma 9V delta 2 T cells. This is in line with the postulated coevolution of the three genes, where occurrence of V gamma 9V delta 2 TCRs coincides with a functional BTN3 molecule.