α-L-Iduronidase (IDUA)為一溶小體酵素，可代謝體內的酸性黏多醣，此酵素缺乏將造成黏多醣在體內廣泛的儲積，而導致體染色體隱性遺傳之第一型黏多醣儲積症。和MPSI相關的IDUA 基因已被分離並定序，國外MPS I病患IDUA基因突變的分析研究顯示IDUA基因呈現高度異質性突變及高度多型性變化。
先前本實驗室已將台灣的一位MPS IH/S中間型患者IDUA cDNA選殖並加以定序分析，結果顯示患者為異型合子的突變，在對偶基因1上有M1I及△54-100(表現子2的缺失)兩種變異；在對偶基因2上則有M193I及△325-343(部分表現子8的缺失)兩種變異。本實驗延續此個案分子致因的探討，結果發現患者位於對偶基因1上的M1I變異係遺傳自母親，表現子2的缺失則為選擇性裁接所導致；位於對偶基因2上的M193I及△325-343變異則遺傳自父親，△325-343係源自於表現子8的點突變(Y343X)造成裁接錯誤所致。此外分別將含變異點的M193I、M1I+△54-100、Y343X的IDUA cDNA重組質體經轉移至CHO-K1細胞中後，所表現IDUA酵素活性分別為正常IDUA cDNA質體所表現的62.5%、10.5%、5.9%。以北方吸漬法分析重組質體轉移細胞株的IDUA mRNA表現量，發現各重組質體轉移細胞株的IDUAmRNA表現量並無明顯的差異。
在多型性分析方面，我們自正常人族群中逢機取樣72個樣品，測定各樣品白血球IDUA酵素活性，並以聚合酵素鏈反應(PCR)放大包含多型性點A8、A20、L118、A314、T388、T410、R489的DNA片段後，再以限制片段長度多型性(RFFLP)或對偶基因專一性的寡核甘酸(ASO)方法檢視各樣品之多型性，結果得到各點多型性的對偶基因頻率及異型合子率，並發現各樣品之A8、虹0多型性基因型完全相同，且A314'T388'T410'R489 多型性基因型亦完全相同，即A8、叱山的多型性對偶基因連鎖於同一染色體上，A314'T388'T410'R489的多型性對偶基因亦連鎖於同一染色盤上。此外也發現LI18不具多型性的對偶基因。1"及心14具多型性的對偶基因"2"和高mUA酵素活性相關，即LI18，心14的I，2單套型和高IDUA酵素活性相關。R489的DNA片段後，再以限制片段長度多型性(RFLP)或對偶基因專一性的寡核甘酸(ASO)方法檢視各樣品之多型性，結果得到各點多型性的對偶基因頻率及異型合子率，並發現各樣品之A8、A20多型性基因型完全相同，且A314、T388、T410、R489多型性基因型亦完全相同，即A8、A20的多型性對偶基因連鎖於同一染色體上，A314、T388、T410、R489的多型性對偶基因亦連鎖於同一染色體上。此外也發現L118不具多型性的對偶基因"1"及A314具多型性的對偶基因"2"和高IDUA酵素活性相關，即L118,A314的1,2單套型和高IDUA酵素活性相關。

α-L-Iduroindase (IDUA) is one of the lysosomal enzymes involved in metabolic degradation of cellular glycosaminoglycans. Loss or marked reduction of IDUA activity results in the autosomal recessive mucopolysaccharidosis type I (MPS I) disease. Recently, the IDUA gene was cloned and the cDNA sequence determined. Mutation screening in patients with MPS I identified a number of mutations and polymorphisms within IDUA gene.
We had investigated the molecular lesions of a Chinese MPS IH/S patient by RT-PCR (polymerase chain reaction) and DNA sequencing. The results revealed that the patient has heterozygous mutations, in which allele 1 has M1I and △54-100 (in-frame deletion of codons 54-100 in exon 2), and allele 2 has M193I and △325-343 (in-frame deletion of codons 325-343 in exon 8). In the present study, the molecular lesions of the patient was further characterized. The results revealed that M1I mutation in allele 1 was maternally inherited, and the deleted exon 2 in M1I allele was due to alternative splicing. The M193I and △325-343 mutations in allele 2 was paternally inherited. However, △325-343 was resulted from a C-to-G transversion in exon 8 (Y343X) which leads to the in-frame deletion of codons 325-343. Expression of M193I, M1I+△54-100 and Y343X in CHO-K1 cells showed retention of 62.5%, 10.5% and 5.9% IDUA activity, respectively. However, the steady-state IDUA mRNA level in the transfected cells remained the same, as indicated by northern blotting.
The correlation of polymorphic DNA haplotypes of the IDUA gene and IDUA activity in Chinese subjects was also investigated in this study. The leukocyte IDUA activity was determined from randomly sampled 72 normal individuals. Genomic DNA extracted from the 72 samples was used to amplify DNA fragment containing the polymorphic change site A8, A20, L118, A314, T388, T410 or R489. To obtain the polymorphic allele frequency and heterozygosity, the PCR-amplified products were analyzed by restriction fragment length polymorphism (RFLP) or allele specific oligonucleotide (ASO) hybridization. For any individual tested, the same genotypes of A8/A20 or A314/T388/T410/R489 were observed. The results suggest that A8, A20 polymorphisms were closely linked, and A314, T388, T410, R489 polymorphisms were also closely linked. Of the haplotypes constructed by L118 and A314, a positive correlation between 1,2 (L118, A314) haplotype and IDUA activity was observed.