遺伝性ニューロパチー(Charcot-Marie-Tooth病)の遺伝子解析 : PO遺伝子を中心に

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In this paper we present four novel mutations in the myelin protein zero gene (P0 gene), which encodes the major structural protein of peripheral nerve myelin (P0) in patients with Charcot-Marie-Tooth disease type 1B (CMT1B) and Dejerine-Sottas syndrome (DS). Seven families and fifteen sporadic patients, who were conformed to have CMT1 or DS by clinical, electro-physiological, or pathological studies, were examined by molecular method. By heteroduplex analysis for exons 1-6 of the P0 gene, one family (Family 7) and three patients (Patient 2, 3, and 4) showed heteroduplex bands indicating mutations of the P0 gene. In family 7, a heterozygous A ?> G substi-tution at nucleotide 389 that generated a 131-Lys ?? Arg transition was identified in exon 3 of the P0 gene. This family was diagnosed as having CMT1B. In Patient 2, a heterozygous G ?> C substitu-tion at nucleotide 499 that generated a 167-Gly -> Arg transition was identified in exon 4 of the P0 gene. In Patient 3, a heterozygous 4 by (GGCA) insertion at nucleotide 560 in the P0 gene was identified. This mutation generated a stop codon at the 14 th codon upstream from the normal ter-mination codon. Patient 2 and 3 were diagnosed with DS. In Patient 4, a heterozygous G ?> A substitution at nucleotide 600 of the PO gene was identified. However, the mutation did not generate a transition of amino acid (polymorphic silent mutation). P0 contains a large glycosylated immunogloblin-like extracellular domain coded by exon 1, 2, and 3 of the P0 gene, a single membrane-spanning domain coded by exon 4 of the P0 gene, and a smaller intracellular domain coded by exon 5 and 6 of the P0 gene. The present study disclosed new muta-tions of the P0 gene encoding the extracellular domain in Family 7, and a membrane-spanning domain in Patient 2 and 3. The mutation of the membrane-spanning domain probably causes more severe phenotypes such as DS and the mutation of the extracellular domain causes less severe phenotypes such as CMT1B. We hypothesize that the variation in clinical severity caused by different mutations in P0 can be explained by the different effects of each mutation. In case of mild CMT1B phenotype, the heterozygous loss-of-function reduces the normal protein present, while dom-inant negative mutations, which affect the formation and function of P0, or homozygous loss-of-function mutations. which completely lack the P0, result in the case of DS.
札幌医科大学の論文
1998-04-01

遺伝性ニューロパチー(Charcot-Marie-Tooth病)の遺伝子解析 : PO遺伝子を中心に

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