Rösby O, Aleström P, Berg K
Institute of Medical Genetics, University of Oslo, Department of Medical Genetics, Ullevål University Hospital, Norway.
Clin Genet. 1997 Nov;52(5):293-302. doi: 10.1111/j.1399-0004.1997.tb04346.x.
In the search for factors contributing to the regulation of the Lp(a) lipoprotein concentration, we have sequenced the kringle IV-type 2 encoding exons 1 and 2 together with the flanking intron sequences of the LPA gene in individuals with different serum concentrations of Lp(a) lipoprotein. The high degree of sequence identity between the kringle IV-type 2 repeats made it possible to analyse all the 3-42 kringles simultaneously by polymerase chain reaction and direct DNA sequencing. The strategy used allowed us to determine approximately 700 bp from each kringle IV-type 2 repeat, resulting in a rapid screen of on average 28,000 bp of the LPA gene from each individual. Comparing these bipartite kringle IV-type 2 repeat sequences from 12 individuals with high and 11 individuals with low Lp(a) lipoprotein level revealed that: 1. no sequence polymorphism could be detected in the exons examined; 2. no sequence polymorphism could be detected in the consensus GT/AG splicing signals of exon/intron junctions; and 3. the proximal intron sequences seemed almost completely conserved in the 76-135 bp analysed. Only one position in the intron sequences exhibited the pattern of a G/A polymorphism. We observed no differences between the group with high and the group with low Lp(a) lipoprotein level. The very high conservation of intron sequences could support the hypothesis that the LPA gene evolved relatively recently. The contradictory finding of a corresponding sequence conservation between the human LPA and the plasminogen gene suggests that an evolutionary pressure has preserved these intron sequences over the last 40-90 million years.
在寻找影响脂蛋白(a)[Lp(a)]浓度调节的因素过程中，我们对不同血清Lp(a)脂蛋白浓度个体的载脂蛋白A[LPA]基因中编码kringle IV型2结构域的外显子1和2及其侧翼内含子序列进行了测序。kringle IV型2重复序列之间的高度序列同一性使得通过聚合酶链反应和直接DNA测序同时分析所有3至42个kringle成为可能。所采用的策略使我们能够从每个kringle IV型2重复序列中确定约700 bp，从而对每个个体的LPA基因平均约28,000 bp进行快速筛查。比较12名高Lp(a)脂蛋白水平个体和11名低Lp(a)脂蛋白水平个体的这些二分kringle IV型2重复序列，结果显示：1.在所检测的外显子中未检测到序列多态性；2.在外显子/内含子连接处的共有GT/AG剪接信号中未检测到序列多态性；3.在所分析的76至135 bp近端内含子序列几乎完全保守。内含子序列中只有一个位置呈现G/A多态性模式。我们未观察到高Lp(a)脂蛋白水平组和低Lp(a)脂蛋白水平组之间存在差异。内含子序列的高度保守可能支持LPA基因相对较新进化而来的假说。人类LPA基因和纤溶酶原基因之间相应序列保守性这一矛盾发现表明，在过去4000万至9000万年中，进化压力一直保留着这些内含子序列。
