α-N-Acetylglucosaminidase (NAGLU)為一種溶小體酵素(lysosomal eneyme)，主要代謝heparan sulfate黏多醣，當酵素活性缺失或顯著降低，將導致體染色體隱性遺傳的第三B型黏多醣儲積症(簡稱MPS IIIB)。NAGLU基因已被分離且定序。本論文主要在探討臺灣MPS IIIB患者的分子致因。聚合酵素鏈反應(PCR)放大包含患者NAGLU基因各表現子片段，經單股核酸構形多型性(SSCP)分析、異偶合(heteroduplex)分析及DNA定序，以檢視患者的基因突變。結果發現患者773為複異型合子的突變，其表現子3上第220個胺基酸密碼的第三個位置缺失核甘酸C (660delC突變)，表現子6上第565個胺基酸密碼發生CGG→TGG的改變(R565W突變)。對偶基因專一的寡核甘酸引子(ASO)雜合的檢測試驗顯示，患者的660delC突變係遺傳自父親，R565W突變則遺傳自母親。患者1146為同型合子的突變，其表現子6上第626個胺基酸密碼發生CGA→TGA的改變(R626X突變)。DdeI切割的檢測試驗顯示患者的父親為R626X突變的異型合子，但母親並無此突變。患者1362、1363兄弟皆為同型合子的突變，其表現子2上第130個胺基酸密碼發生CGC→TGC的改變(R130C突變)。KpnI切割的檢測試驗顯示患者的母親為R130C突變的異型合子。患者1377亦為同型合子的突變，其表現子2上第154個胺基酸密碼發生ATA→AGA的改變(I154R突變)。誤配(mismatch)引子的PCR及HinfI切割的檢測試驗顯示，患者的父母親皆為I154R突變的異型合子。在轉移的COS-7細胞中含660delC、R565W、R626X、Y309C、G412E突變的NAGLU cDNA重組質體，僅表現微量的NAGLU酵素活性(野生型的0.0~3.9)，雖然NAGLU mRNA的表現量並未降低。

α-N-Acetylglucosaminidase (NAGLU) is one of the lysosomal enzymes involved in the stepwise degradation of glycosaminoglycans heparan sulfate. Loss or marked reduction of NAGLU activity results in the autosomal recessive mucopolysaccharidosis type IIIB (MPS IIIB) disease. The purpose of this study was to investigate the molecular lesions of Chinese patients with MPS IIIB. The coding sequences of the NAGLU gene were amplified and examined by single strand conformation polymorphism, heteroduplex, and DNA sequence analyses. Patient 773 has heterozygous mutations; one NAGLU allele has R565W (C-T transition in codon 565) and the other NAGLU allele has 660delC (deletion of nucleotide C at cDNA 660). By allele specific oligonucleotide hybridization analysis, mutation R565W was maternally inherited whereas mutation 660delC paternally inherited. Patient 1146 is homozygous for mutation R626X (C-T transition in codon 626). By DdeI restriction analysis, the mutation was only found in 1146's father. Patients 1362 and 1363 are homozygous for mutation R130C (C-T transition in codon 130). By KpnI restriction analysis, the mutation also appears in their mother. Patient 1377 is homozygous for mutation I154R (T-G transversion in codon 154). By PCR with mismatch primer and HinfI restriction analysis, the mutation was inherited from both parents. In transfected COS-7 cells, NAGLU cDNA containing 60delC, R565W, R626X, Y309C or G412E mutation caused significant reduction in enzyme activity (0.0~3.9 of normal activity), although it did not cause significant reduction in NAGLU mRNA levels.

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