Gonnerman W A, Elliott-Bryant R, Carreras I, Sipe J D, Cathcart E S
E. N. Rogers Memorial Veterans Affairs Hospital, Bedford, Massachusetts 01730, USA.
J Exp Med. 1995 Jun 1;181(6):2249-52. doi: 10.1084/jem.181.6.2249.
Inbred strains of mice provide a model for studies of the pathogenesis of amyloid A (AA) amyloidosis. All susceptible strains of mice described to date codominantly express two serum amyloid A (apoSAA) isoforms, apoSAA1 and apoSAA2, of which only apoSAA2 serves as a precursor for amyloid fibrils. In previous studies, we have shown that the CE/J strain, which produces a single, novel apoSAA isoform, apoSAACE/J, is amyloid resistant. In the present study amyloid-resistant CE/J females were mated with amyloid-susceptible CBA/J males to produce F1 hybrid offspring which were then backcrossed to the parental CBA/J mouse strain. Amyloid susceptibility was determined in 30 backcrossed mice 72 h after injection of murine amyloid enhancing factor and silver nitrate. ApoSAA isoforms in plasma were separated by isoelectric focusing gel electrophoresis and visualized after immunoblotting with anti-AA antiserum. Amyloid A fibrils in spleen homogenates were denatured by formic acid and AA protein was quantified by ELISA using anti-mouse apoSAA antibodies. Values < 5 apoSAA equivalent units were considered negative. 13 mice expressed an apoSAA1 and apoSAA2 doublet characteristic of CBA/J mice, whereas 17 mice, expressed the apoSAACE/J isoform codominantly with apoSAA1 and apoSAA2. The correlation of amyloid resistance to expression of the apoSAACE/J isoform was absolute (17/17 were negative; mean score 2.6 +/- 0.17 [standard error of the mean] apoSAA equivalent units) and the correlation between amyloid susceptibility and the expression of apoSAA2/apoSAA1 was also striking (12/13 were amyloid positive; mean score 47.9 +/- 9.0 [standard error of the mean] apoSAA equivalent units (P < 0.001). This is not significantly different from the 50% segregation of apoSAA phenotypes expected for linkage to a single gene. These results indicate that a single gene governs apoSAACE/J expression and thus confers protection against amyloid deposition even in the presence of apoSAA1 and apoSAA2 isoforms and show for the first time that resistance to AA amyloidosis is a dominant trait governed by a single gene.
近交系小鼠为研究淀粉样蛋白A（AA）淀粉样变性的发病机制提供了一个模型。迄今为止描述的所有易感小鼠品系共显性表达两种血清淀粉样蛋白A（apoSAA）异构体，即apoSAA1和apoSAA2，其中只有apoSAA2作为淀粉样纤维的前体。在先前的研究中，我们已经表明，产生单一新型apoSAA异构体apoSAACE/J的CE/J品系对淀粉样变性具有抗性。在本研究中，将对淀粉样变性具有抗性的CE/J雌性小鼠与易感淀粉样变性的CBA/J雄性小鼠交配，产生F1代杂交后代，然后将其与亲代CBA/J小鼠品系回交。在注射鼠淀粉样增强因子和硝酸银72小时后，对30只回交小鼠的淀粉样变性易感性进行了测定。通过等电聚焦凝胶电泳分离血浆中的apoSAA异构体，并用抗AA抗血清进行免疫印迹后进行可视化。脾脏匀浆中的淀粉样蛋白A纤维用甲酸变性，并用抗小鼠apoSAA抗体通过ELISA对AA蛋白进行定量。apoSAA等效单位值<5被认为是阴性。13只小鼠表达了CBA/J小鼠特有的apoSAA1和apoSAA2双峰，而17只小鼠共显性表达了apoSAACE/J异构体与apoSAA1和apoSAA2。对淀粉样变性的抗性与apoSAACE/J异构体表达之间的相关性是绝对的（17/17为阴性；平均得分2.6±0.17[平均标准误差]apoSAA等效单位），淀粉样变性易感性与apoSAA2/apoSAA1表达之间的相关性也很显著（12/13为淀粉样阳性；平均得分47.9±9.0[平均标准误差]apoSAA等效单位（P<0.001）。这与预期的与单个基因连锁的apoSAA表型的50%分离没有显著差异。这些结果表明，单个基因控制apoSAACE/J的表达，因此即使在存在apoSAA1和apoSAA2异构体的情况下也能提供对淀粉样蛋白沉积的保护，并且首次表明对AA淀粉样变性的抗性是由单个基因控制的显性性状。
