Phylogenetic and developmental study of CD4, CD8 α and β T cell co-receptor homologs in two amphibian species, Xenopus tropicalis and Xenopus laevis
Phylogenetic and developmental study of CD4, CD8 α and β T cell co-receptor homologs in two amphibian species, Xenopus tropicalis and Xenopus laevis
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DOI：
10.1016/j.dci.2010.11.005
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发表时间：
2011-03-01
影响因子：
2.9
通讯作者：
Robert, Jacques
中科院分区：
文献类型：
--
作者：
Chida, Asiya Seema;Goyos, Ana;Robert, Jacques
CD 4和CD 8共受体通过与T细胞受体和MHC分子相互作用在T细胞发育和活化中起关键作用。尽管这些基因的同源物已在许多有颌脊椎动物中被鉴定出来，但关于它们在MHC相互作用和T细胞功能中的进化和特化仍然存在未解决的差距。使用实验和计算程序，我们确定了CD 4。热带爪蟾（Xenopus tropicalis）及其姊妹种非洲爪蟾（Xenopus laevis）的CD 8 α和CD 8 β基因同源物，其全基因组已被测序。推导的氨基酸序列的多重比对显示，在非哺乳动物物种中，参与CD 4与MHC II类和CD 8 α与I类结合的残基保守性较差，推测与MHC和II基因的共同进化压力有关。系统发育研究表明，异足亚目共受体基因与其他四足动物的同源基因的关系比硬骨鱼类更为密切。此外，这些基因在非洲爪蟾中的发育和细胞特异性表达模式与哺乳动物非常相似。X.哺乳动物CD 4主要由外周非CD 8 T细胞表达，并且早在胸腺器官发生开始时受精后（dpf）4天就在胸腺中检测到。CD 8 β表达对成人表面CD 8（+）T细胞和胸腺细胞具有特异性，并且在5 dpf时首次在胸腺中检测到，与产生性TCR γ转录平行，而在7-9 dpf之前未检测到产生性TCR β和α重排。(C)2010爱思唯尔有限公司保留所有权利。
CD4 and CD8 co-receptors play critical roles in T cell development and activation by interacting both with T cell receptors and MHC molecules. Although homologs of these genes have been identified in many jawed vertebrates, there are still unresolved gaps concerning their evolution and specialization in MHC interaction and T cell function. Using experimental and computational procedures we identified CD4. CD8 alpha and CD8 beta gene homologs both in Xenopus tropicalis, whose full genome has been sequenced, and its sister species Xenopus laevis. Multiple alignments of deduced amino acid sequences reveal a poor conservation of the residues involved in binding of CD4 to MHC class II, and CD8 alpha to class I in non-mammalian species, presumably related to the co-evolutionary pressure of MHC land II genes. Phylogenetic study suggests that Xenopodinae co-receptor genes are more closely related to their homologs in other tetrapods than those of bony fish. Furthermore, the developmental and cell-specific expression patterns of these genes in X laevis are very similar to that of mammals. X. laevis CD4 is mainly expressed by peripheral non-CD8 T cells and detected in the thymus as early as four days post-fertilization (dpf) at the onset of thymic organogenesis. CD8 beta expression is specific to adult surface CD8(+) T cells and thymo-cytes, and is first detected in the thymus at 5 dpf in parallel with productive TCR gamma transrcipts, whereas productive TCR beta and alpha rearrangements are not detected before 7-9 dpf. (C) 2010 Elsevier Ltd. All rights reserved.