A control mechanism of gene expression in red cell membranes

(1)红细胞膜疾病的表型特征：在我们两年的研究期间(1998和1999年)，我们研究了135个先天性红细胞膜疾病家系的175例，其中包括遗传性球形红细胞增多症(HS)100个家系的118例患者。通过临床血液学、膜蛋白生化、分子电子显微镜和生物物理分析确定临床表型。(Ii)HS的基因分型分析：在带3基因(EPB3)上检测到12个致病基因突变：4个移码突变和8个错义突变，7个基因多态性。在Ank1基因上，发现16个致病基因突变(4个无义突变、8个移码突变和4个异常剪接)，17个基因多态性(2个错义突变和15个沉默突变)。在蛋白4.2基因(ELB42)上，发现了3个致病基因错义突变。(Iii)红系分化过程中膜蛋白的顺序表达：在人红细胞膜上，血影蛋白和带3在早期红系前体细胞中表达，其次是蛋白4.1，最后蛋白4.2在很晚的红细胞中表达。(4)在SPTB中，EPB3、SPTB和ELB42启动子区域的5‘-CpG-3’位点甲基化状态，所有5‘-CpG-3’位完全未甲基化，而EPB3几乎完全甲基化。在ELB42中，在非常早期的红细胞中没有甲基化，尽管在成熟的红系细胞中所有的位置几乎完全甲基化。

(I) Characterization of the phenotypes of red cell membrane disorders :During our research term for 2 years (1998 and 1999), we have studied 175 cases from 135 kindred of congenital red cell membrane disorders including 118 patients from 100 kindred of hereditary spherocytosis (HS). Clinical phenotypes were determined by clinical hematology studies, membrane protein biochemistry, molecular electron microscopy, and biophysical analyses.(II) Genotypic analyses in HS :On the band 3 gene (EPB3), 12 pathognomonic mutations were detected : 4 frameshift mutations and 8 missense mutations with 7 gene polymorphisms. On the ankyrin gene (ANK1), 16 pathognomonic mutations (4 nonsense mutations, 8 frameshift mutations, and 4 abnormal splicings) with 17 gene polymorphisms (2 missense mutations and 15 silent mutations) were identified. On the protein 4.2 gene (ELB42), 3 pathognomonic missense mutations had been found.(III) Sequential expression of membrane proteins during erythroid differentiation :In human red cell membranes, spectrins and band 3 were expressed in early erythroid precursors, protein 4.1 followed, and protein 4.2 was finally expressed at the very late erythroblasts sequentially.(IV) The state of methylation of 5'-CpG-3' sites of the promoter regions of EPB3, SPTB, and ELB42In SPTB, all of the 5'-CpG-3' sites were totally unmethylated, in contrast to nearly total methylation in EPB3. In ELB42, methylation was absent in very early erythroblasts, although all the sites were nearly completely methylated in mature erythroid cells.