Allorecognition in Ciona intestinalis: molecular basis for self-sterility in a hermaphroditic urochordate

祖先的脊索动物如何区分自我和非自我尚不清楚。在无偏筛选方法中，我们鉴定了在同种异体接触后表达发生改变的Botryllus基因，我们最近在Botryllus（Khalturin et al，2003）以及单独的被囊类玻璃海鞘和C. savignyii（Khalturin等人，2004年a）。在脊椎动物中，CD 94的配体属于非经典MHC I的HLA-E组。由于尾索动物的基因组不包含任何MHC样基因，因此尾索动物中CD 94样受体蛋白的配体的性质仍然是个谜。在这里，我们建议进一步分析祖先脊索动物的同种异体识别机制。具体而言，我们建议（i）确定的配体的CD 94样蛋白的葡萄和玻璃海鞘;（ii）分析推定的NK基因座在玻璃海鞘和葡萄;和（iii）筛选蛋白质与高度个体间变异的玻璃海鞘。这一结果将有助于了解后口动物先天免疫系统的进化以及适应性免疫的出现。

How ancestral chordates discriminate between self and nonself is not known. In an unbiased screening approach to identify Botryllus genes whose expression is altered in response to allogeneic contacts we recently identified a homolog of the CD94 / NKR-P1 receptor in Botryllus (Khalturin et al, 2003) as well as in the solitary tunicates Ciona intestinalis and C. savignyii (Khalturin et al., 2004a). In vertebrates, ligands to CD94 belong to the HLA-E group of nonclassical MHC I. Since the genomes of urochorda tes do not contain any MHC-like genes, the nature of the ligand of the CD94-like receptor protein in urochordates remains enigmatic. Here we propose to further analyse the mechanisms of allorecognition in ancestral chordates. Specifically, we suggest to (i) identify the ligand for CD94-like proteins in Botryllus and Ciona; (ii) analyse the putative NK locus in Ciona and Botryllus; and (iii) screen for proteins with high degree of interindividual variability in Ciona. The results will shed light on the evol ution of the innate immune system in deuterostomes as well as on the emergence of adaptive immunity.