Smit M, de Knijff P, Sijts A, Klasen E C, Frants R R, Havekes L M
Department of Human Genetics, State University Leiden, The Netherlands.
Hum Hered. 1988;38(5):277-82. doi: 10.1159/000153799.
The genes coding for the apolipoproteins E, C1 and C2 are clustered on the long arm of chromosome 19 in a region of approximately 45 kilobases (kb). In a normolipidemic individual, we detected a new apoE variant with an isoelectric point between that of E3 and E4. As this variant lacks cysteine residues and has probably arisen from an E4 allele, it is designated E4. To gain further insight into the origin of the mutation, the haplotypes of the propositus were extended by restriction fragment length polymorphism (RFLP) analysis of the family. The apoE variant cosegregates with the H2 allele of the HpaI polymorphism visualized with an APOE probe and with a new rare 4.5-kb fragment (T3) of the TaqI RFLP detectable with an APOC2 probe. As the propositus and the first-degree relatives with this unique haplotype are normolipidemic, this apoE variant does not seem to be associated with disturbances in the lipoprotein metabolism.
编码载脂蛋白E、C1和C2的基因聚集在19号染色体长臂上一个约45千碱基（kb）的区域。在一名血脂正常的个体中，我们检测到一种新的载脂蛋白E变体，其等电点介于E3和E4之间。由于该变体缺乏半胱氨酸残基且可能源自E4等位基因，故将其命名为E4。为了进一步深入了解该突变的起源，通过对该家族进行限制性片段长度多态性（RFLP）分析，扩展了先证者的单倍型。该载脂蛋白E变体与用APOE探针可视化的HpaI多态性的H2等位基因以及用APOC2探针可检测到的TaqI RFLP的一个新的罕见4.5 kb片段（T3）共分离。由于具有这种独特单倍型的先证者和一级亲属血脂正常，这种载脂蛋白E变体似乎与脂蛋白代谢紊乱无关。
