Genotypic and phenotypic expressions of hereditary red cell membrane disorders

(I)日本红细胞膜疾病的表型特征：我们研究了来自100个遗传性球形红细胞增多症（HS）家族的118例病例，HS是日本最常见的红细胞膜疾病。其中30个家系中48例为常染色体显性遗传型，70个家系中70例为非常染色体显性遗传型。两组的临床特征几乎相同。表型上，四分之一的HS患者中观察到带3（B3）缺乏，三分之一的HS患者中观察到蛋白4.2（P4.2）缺乏。几乎没有锚蛋白（ANK）缺乏的病例。在三分之一的HS中，没有观察到膜蛋白的可检测的缺陷。(II)HS的基因型特征：在B3基因（EPB 3）中检测到12个HS特异性突变，其中4个移码突变和8个错义突变，以及7个基因多态性。在ANK基因（ANK 1）中，有16个特异性突变（4个无义突变，8个移码突变和4个异常剪接）和17个基因多态性（2个错义突变和15个沉默突变）。在P4.2基因（ELB 42）中，检测到3个关键错义突变（P4.2 Nippon、P4.2滋贺和P4.2小松）。(III)甲基化状态作为基因表达的控制机制：研究了B3基因（EPB 3）、P4.2基因（ELB 42）和β-血影蛋白基因（SPTB）启动子区5-C pG-3'位点的甲基化状态。这些位点是高度甲基化敏感的。SPTB始终未甲基化，EPB 3基本上甲基化，而ELB 42的甲基化状态由极早期红系祖细胞的“未甲基化”转变为成熟红系细胞的“甲基化”，并伴随ELB 42 mRNA和P4.2蛋白的表达。

(I) Phenotypic features of red cell membrane disorders in Japan :We have studied 118 cases from 100 kindred of hereditary spherocytosis (HS), which is the most common red cell membrane disorder in Japan. Among them, 48 cases of 30 kindred were HS of autosomal dominant (AD) transmission, and 70 cases of 70 kindred were those of non-AD type. Clinical features were nearly identical in the two groups. Phenotypically, band 3 (B3) deficiency was observed in one-fourth of HS patients, and protein 4.2 (P4.2) in one-third. There was nearly no cases with ankyrin (ANK) deficiency. In one-third of HS, no detectable deficiency of membrane proteins was observed.(II) Genotypic features of HS :12 mutations pathognomonic for HS were detected in the B3 gene (EPB3) : 4 frameshift mutations and 8 missense mutations, in addition to 7 gene polymorphisms. In the ANK gene (ANK1), there were 16 pathognomonic mutations (4 nonsense mutations, 8 frameshift mutations, and 4 abnormal splicings) with 17 gene polymorphisms (2 missense and 15 silent mutations). In the P4.2 gene (ELB42), 3 critical missense mutations (P4.2 Nippon, P4.2 Shiga, and P4.2 Komatsu) were detected.(III) Methylation status as a control mechanism of gene expression :The state of methylation was studied at the 5-C pG-3' sites in the promoter region of the B3 gene (EPB3), the P4.2 gene (ELB42), and β-spectrin gene (SPTB). These sites were highly methylation-sensitive. SPTB was always unmethylated, and EPB3 was substantially methylated.However, the state of methylation in ELB42 was switched from "unmethylated" in very early erythroid progenitors to "methylated" in mature erythroid cells, concomitant to the expression of mRNA of ELB42 and of P4.2 protein.