Haire R N, Ota T, Rast J P, Litman R T, Chan F Y, Zon L I, Litman G W
Department of Pediatrics, University of South Florida College of Medicine, All Children's Hospital, St. Petersburg 33701, USA.
J Immunol. 1996 Aug 15;157(4):1544-50.
Xenopus laevis is a unique model for studying the ontogenetic development of immune functions. A short primer PCR amplification method was employed to amplify fragments from Xenopus genomic DNA that are related to Ig light chains and TCR. One fragment was identified that appeared to represent a novel type of light chain and was used as a probe to recover the corresponding cDNA from a spleen cDNA library. We designate these light chains type III. Using an iterative screening procedure, six families of VL genes, two distinct JL and two distinct CL sequences, were identified. In a comparison of phylogenetically diverse light chains, the type III genes align with higher vertebrate lambda genes. Southern blot hybridization analyses with genomic DNA from different animals showed the VL and CL sequences to be both diverse and polymorphic. Intrafamily sequence comparisons of VL genes revealed additional diversity. Collectively, these studies confirm the existence of a third type of light chain gene in Xenopus, establish a high degree of genetic variation in the sequences encoding the light chain V regions, and provide the most significant evidence to date for the presence of a lambda-like light chain gene at the phylogenetic level of the amphibians.
非洲爪蟾是研究免疫功能个体发育的独特模型。采用短引物PCR扩增方法，从非洲爪蟾基因组DNA中扩增出与免疫球蛋白轻链和T细胞受体相关的片段。鉴定出一个似乎代表新型轻链的片段，并将其用作探针从脾脏cDNA文库中回收相应的cDNA。我们将这些轻链命名为III型。通过迭代筛选程序，鉴定出六个VL基因家族、两个不同的JL和两个不同的CL序列。在对系统发育上不同的轻链进行比较时，III型基因与高等脊椎动物的λ基因对齐。用不同动物的基因组DNA进行Southern印迹杂交分析表明，VL和CL序列既多样又具有多态性。VL基因的家族内序列比较揭示了更多的多样性。总体而言，这些研究证实了非洲爪蟾中存在第三种轻链基因，在编码轻链V区的序列中建立了高度的遗传变异，并为两栖动物系统发育水平上存在类似λ的轻链基因提供了迄今为止最有力的证据。
