Molecular Genetic Study of Mouse Senile Amyloidosis

采用聚合酶链反应（PCR）从9个近交系小鼠染色体DNA中扩增出apoA-II基因。PCR产物序列分析显示存在3种apoA-II基因。根据apoA-II cDNA的核苷酸序列预测出3种类型的apoA-II蛋白（A、B和C）。氨基酸残基在4个位置被取代。利用限制性内切酶Cfr13I和MspI对PCR扩增的apoA-II DNA进行酶切鉴定。小鼠品系SAM-P/1、SAM-P/2、SJL/J、A/J具有A型apoA-II。这些菌株通常表现出淀粉样蛋白沉积从相对年轻的年龄。对F2杂交小鼠的apoA-II型和淀粉样蛋白沉积的检测表明，apoA-II淀粉样蛋白沉积仅存在于纯合的A型apoA-II小鼠中。我们推测apoA-II的分子结构可能是参与小鼠老年性淀粉样变发生的一个重要因素。SAM-P/1小鼠肝脏中apoA-II mRNA的表达水平随着年龄的增长而迅速下降。14月龄时apoA-II mRNA表达水平为2月龄时的50%。建立了淀粉样蛋白原纤维特异性测定系统，并对淀粉样蛋白原纤维聚合动力学进行了分析。

The apoA-II gene was amplified by polymerase chain reaction (PCR) from chromosomal DNA of nine inbred strains of mice. Sequence analysis of the PCR products indicated the presence of three types of apoA-II genes. Three types of apoA-II proteins (A, B and C) were predicted from the nucleotide sequence of apoA-II cDNA. Substitution of amino acid residues was noted at 4 positions. Each type was identifiable by digestion of PCR amplified apoA-II DNA, using restriction enzyme Cfr13I and MspI. The mouse strains, SAM-P/1, SAM-P/2, SJL/J, A/J had type A apoA-II. These strains generally exhibit amyloid deposition from relatively younger age. Examination of types of apoA-II and amyloid deposition in the F2 hybrid mice showed that apoA-II amyloid deposition was present only in the homozygous mice for type A apoA-II. We postulate that the molecular structure of apoA-II may be an important factor involved in the development of senile amyloidosis in mice.The expression levels of apoA-II mRNA in the liver of the SAM-P/1 strains of mice decreased rapidly with advancing age. The expression levels of apoA-II mRNA at the age of 14 months was 50 % of the level at the age of 2 months.The new system was developed for determination of amyloid fibrils specifically and kinetics of amyloid fibril polymerization was analyzed.