Genotypic and phenotypic expressions of hereditary red cell membrane disorders

(1)日本红细胞膜疾病的表型特征：我们研究了日本最常见的遗传性球形细胞增多症(HS)100个家系的118例红细胞膜疾病。其中常染色体显性遗传(AD)家系48例，非AD家系70例。两组患者的临床特征几乎相同。表型上，1/4的HS患者出现带3(B3)缺失，1/3的患者出现蛋白4.2(P4.2)缺失。几乎没有锚蛋白(ANK)缺乏症病例。(2)HS的基因特征：在Hs的B3基因(EPB3)上检测到12个致病突变：4个移码突变和8个错义突变，以及7个基因多态性。ANK基因(ANK1)有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P4.2基因(ELB42)中，检测到3个关键的错义突变(P4.2 Nippon、P4.2 Shiga和P4.2 Komatsu)。(3)甲基化状态作为基因表达的控制机制：研究了B3基因启动子区域(EPB3)、P4.2基因(ELB42)和β-Spectrin基因(SPTB)启动子区域5-C Pg-3‘位点的甲基化状态。这些位点对甲基化高度敏感。但在早期的红系祖细胞中，ELB42的甲基化状态从非常早期的红系祖细胞的“未甲基化”状态转变为成熟的红系细胞中的“甲基化”状态，伴随着ELB42的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.