Kasturi K N, Yio X Y, Bona C A
Department of Microbiology, Mount Sinai School of Medicine, New York, NY 10029-6574.
Proc Natl Acad Sci U S A. 1994 Aug 16;91(17):8067-71. doi: 10.1073/pnas.91.17.8067.
Tight-skin mouse, a mutant strain with a single gene defect, develops cutaneous hyperplasia and specific autoantibodies, like humans affected by scleroderma. The autoantibodies produced in the tight-skin mouse are encoded primarily by heavy-chain variable (VH) genes from the J558 family. To understand the genetic basis of production of autoantibodies, we have analyzed the structure of J558 genes encoding these autoantibodies. The results showed that J558 genes encoding these antibodies were not derived from a selected germ-line gene(s) or a single subfamily but were derived from genes belonging to diverse J558 subfamilies. However, two prototype VH genes representing two new subfamilies were found to be repeatedly expressed in their germ-line form in eight independent clones. Autoantibodies with distinct specificities appear to be generated by pairing of similar/identical VH genes with different V kappa genes derived from the same or different families. Fourteen of 18 autoantibodies shared a conserved heptapeptide sequence motif, YNEKFKG, in the second complementarity-determining region of heavy chains. Usage of germ-line genes from diverse J558 subfamilies bearing a common motif to encode autoantibodies suggests a regulatory role for this motif. Thus, selection and expansion of the autoreactive B-cell repertoire in the tight-skin mouse appear to be VH-gene mediated. The frequency of N nucleotide addition at diversity-joining (D-JH) junctions was lower, whereas the frequency of usage of the DFL16 segment was higher. Finally, in contrast to normal and other autoimmune mouse strains, the frequencies of D-D fusions and D inversions were higher in tight-skin mouse total immunoglobulin as well as autoantibody repertoires.
紧皮小鼠是一种具有单基因缺陷的突变品系，会出现皮肤增生并产生特异性自身抗体，类似于患硬皮病的人类。紧皮小鼠产生的自身抗体主要由来自J558家族的重链可变（VH）基因编码。为了解自身抗体产生的遗传基础，我们分析了编码这些自身抗体的J558基因的结构。结果表明，编码这些抗体的J558基因并非源自选定的种系基因或单个亚家族，而是源自属于不同J558亚家族的基因。然而，代表两个新亚家族的两个原型VH基因在八个独立克隆中以种系形式反复表达。具有不同特异性的自身抗体似乎是由相似/相同的VH基因与来自相同或不同家族的不同Vκ基因配对产生的。18种自身抗体中有14种在重链的第二个互补决定区共享一个保守的七肽序列基序YNEKFKG。来自具有共同基序的不同J558亚家族的种系基因用于编码自身抗体，这表明该基序具有调节作用。因此，紧皮小鼠中自身反应性B细胞库的选择和扩增似乎是由VH基因介导的。在多样性连接（D-JH）连接处添加N核苷酸的频率较低，而DFL16片段的使用频率较高。最后，与正常和其他自身免疫小鼠品系相比，紧皮小鼠总免疫球蛋白以及自身抗体库中D-D融合和D倒位的频率更高。
