Mutational analysis of the α-l-iduronidase gene in 10 unrelated Korean type I mucopolysaccharidosis patients: Identification of four novel mutations

Quantification of Idua Enzymatic Activity Combined with Observation of Phenotypic Change in Zebrafish Embryos Provide a Preliminary Assessment of Mutated idua Correlated with Mucopolysaccharidosis Type I

Mucopolysaccharidosis type I (MPS I) is an inherited autosomal recessive disease resulting from mutation of the α-l-Iduronidase (IDUA) gene. New unknown mutated nucleotides of idua have increasingly been discovered in newborn screening, and remain to be elucidated. In this study, we found that the z-Idua enzymatic activity of zebrafish idua-knockdown embryos was reduced, resulting in the accumulation of undegradable metabolite of heparin sulfate, as well as increased mortality and defective phenotypes similar to some symptoms of human MPS I. After microinjecting mutated z-idua-L346R, -T364M, -E398-deleted, and -E540-frameshifted mRNAs, corresponding to mutated human IDUA associated with MPS I, into zebrafish embryos, no increase in z-Idua enzymatic activity, except of z-idua-E540-frameshift-injected embryos, was noted compared with endogenous z-Idua of untreated embryos. Defective phenotypes were observed in the z-idua-L346R-injected embryos, suggesting that failed enzymatic activity of mutated z-Idua-L346R might have a dominant negative effect on endogenous z-Idua function. However, defective phenotypes were not observed in the z-idua-E540-frameshifted-mRNA-injected embryos, which provided partial enzymatic activity. Based on these results, we suggest that the z-Idua enzyme activity assay combined with phenotypic observation of mutated-idua-injected zebrafish embryos could serve as an alternative platform for a preliminary assessment of mutated idua not yet characterized for their role in MPS I.

Mucopolysaccharidosis Type I in the Russian Federation and Other Republics of the Former Soviet Union: Molecular Genetic Analysis and Epidemiology

Mutations in the IDUA gene cause deficiency of the lysosomal enzyme alpha-l-iduronidase (IDUA), which leads to a rare disease known as mucopolysaccharidosis type I. More than 300 pathogenic variants of the IDUA gene have been reported to date, but not much is known about the distribution of mutations in different populations and ethnic groups due to the low prevalence of the disease. This article presents the results of a molecular genetic study of 206 patients with mucopolysaccharidosis type I (MPS I) from the Russian Federation (RF) and other republics of the former Soviet Union. Among them, there were 173 Russian (Slavic) patients, 9 Tatars, and 24 patients of different nationalities from other republics of the former Soviet Union. Seventy-three different pathogenic variants in the IDUA gene were identified. The common variant NM_000203.5:c.208C>T was the most prevalent mutant allele among Russian and Tatar patients. The common variant NM_000203.5:c.1205G>A accounted for only 5.8% mutant alleles in Russian patients. Both mutations were very rare or absent in patients from other populations. The pathogenic variant NM_000203.5:c.187C>T was the major allele in patients of Turkic origin (Altaian, Uzbeks, and Kyrgyz). Specific own pathogenic alleles in the IDUA gene were identified in each of these ethnic groups. The identified features are important for understanding the molecular origin of the disease, predicting the risk of its development and creating optimal diagnostic and treatment tools for specific regions and ethnic groups.

Mutation Analysis of the IDUA Gene in Iranian Patients with Mucopolysaccharidosis Type 1: Identification of Four Novel Mutations

Background and Purpose: Mucopolysaccharidosis 1 (MPS1) is an autosomal recessive disorder of a lysosomal enzyme called alpha-l-iduronidase caused by mutations in the IDUA gene. This enzyme is responsible for the degradation of the mucopolysaccharides, heparan sulfate, and dermatan sulfate. Based on clinical features and enzyme deficiency, MPS1 is divided into three subtypes, including a severe subtype (Hurler syndrome), an intermediate subtype (Hurler-Scheie syndrome), and an attenuated subtype (Scheie syndrome). The objective of this study was to characterize the mutation profiles of 17 Iranian patients with MPS1 and characterize the clinical features associated with their genotypes. Materials and Methods: Polymerase chain reaction-based sequencing of the IDUA gene was carried out for 10 patients with clinical diagnoses of MPS1 and 50 healthy controls. To estimate the impact of newly identified variants on the structure and function of the encoded alpha-l-iduronidase, in silico analyses was performed. Results: Eight genetic variations were detected, including five missense mutations (p.M1L, p.G51D, p.G134V, p.S157P, p.D301E), two nonsense mutations (p.W402* and p.Y343*), and one deletion (p.GFLNYY197-202), among which p.G134V, p.S157P, p.D301E, and p.GFLNYY197-202 were novel variations that had not been previously reported. Conclusion: After combining the results of the two previous IDUA gene studies performed on Iranian MPS1 patients and the results obtained from the current study, it is inferred that despite the presence of a number of previously known mutations, about half of the detected variations were unique in Iranian patients.

Comment on "report of 5 novel mutations of the α-L-iduronidase gene and comparison of Korean mutations in relation with those of Japan or China in patients with mucopolysaccharidosis I"

In this comment, we highlight that the IDUA pathogenic variants 704ins5 and c.613_617dupTGCTC are the same, but have different names depending on the nomenclature guideline used. Therefore, the frequency of this variant is 17.6% of alleles in Korean patients. This commentary stresses the importance of proper variant annotation and the use of guidelines when describing or reviewing mutations.

Report of 5 novel mutations of the α-L-iduronidase gene and comparison of Korean mutations in relation with those of Japan or China in patients with mucopolysaccharidosis I

BACKGROUND

Mucopolysaccharidosis I (MPS I) is an autosomal recessive lysosomal storage disorder caused by a lack of the lysosomal enzyme α-L-iduronidase (IDUA). To date, more than 200 IDUA mutations have been reported. However, only a few types of mutations are recurrent and the frequencies of mutations differ from country to country.

METHODS

We performed the IDUA mutation analysis in seven patients who were biochemically diagnosed with MPS I in the Department of Pediatrics, Samsung Medical Center, from 2009 to 2014. Here, we describe the results of the IDUA mutation analysis in seven patients with MPS I and the IDUA mutational spectrum in Korean patients with MPS I, including previous data.

RESULTS

The IDUA mutations were found in all 14 alleles of 7 patients, and 11 kinds of IDUA mutations were identified. The detected mutations were five missense mutations (p.A79V, p.L346R, p.T388K, p.P496R, and p.C577Y), two nonsense mutations (p.Y618* and p.R628*), two deletions (c.683delC and c.1591delC), one splice site mutation (c.972+1G>A), and one duplication (c.613_617dup). Among these, p.T388K, p.C577Y, c.683delC, c.1591delC, and c.972+1G>A were novel mutations that have not previously been reported. After taking everything into consideration, including IDUA mutation analysis of the previously reported 10 unrelated Korean patients with MPS I, p.L346R and c.704ins5 were most commonly found in Korean patients with MPS I. However, p.W402* and p.Q70*, which have mainly been found in Caucasian patients, were not found.

CONCLUSION

As a result, p.L346R and c.704ins5, which were the most common in Korea, which is geographically situated midway between China and Japan, were some of the most common mutations in China and Japan, respectively. These results are especially worthy of notice.

An overview of Korean patients with mucopolysaccharidosis and collaboration through the Asia Pacific MPS Network

Mucopolysaccharidosis (MPS) is a constellation of disorders characterized by the accumulation of mucopolysaccharides in tissues and organs. This accumulation results in the deterioration and degeneration of multiple organs. This paper describes the general distribution of types of MPS in patients, their clinical characteristics and genotypes, the development of animal studies and preclinical studies, enzyme replacement therapy in South Korea, and the development of idursulfase beta and clinical trials on idursulfase beta in South Korea. In addition, this paper discusses academic collaboration among specialists in MPS care in the Asia-Pacific region, which includes Japan, Taiwan, Malaysia, and South Korea, through an organization called the Asia-Pacific MPS Network (APMN). The Asia-Pacific MPS Registry, an electronic remote data entry system, has been developed by key doctors in the APMN. Rare diseases require international cooperation and collaboration to elucidate their mechanisms and carry out clinical trials; therefore, an organization such as the APMN is required. Furthermore, international collaboration among Asian countries and countries around the world will be of utmost importance in the future.

Three novel α-L-iduronidase mutations in 10 unrelated Chinese mucopolysaccharidosis type I families

Mucopolysaccharidosis type I (MPS I) arises from a deficiency in the α-L-iduronidase (IDUA) enzyme. Although the clinical spectrum in MPS I patients is continuous, it was possible to recognize 3 phenotypes reflecting the severity of symptoms, viz., the Hurler, Scheie and Hurler/Scheie syndromes. In this study, 10 unrelated Chinese MPS I families (nine Hurler and one Hurler/Scheie) were investigated, and 16 mutant alleles were identified. Three novel mutations in IDUA genes, one missense p.R363H (c.1088G > A) and two splice-site mutations (c.1190-1G > A and c.792+1G > T), were found. Notably, 45% (nine out of 20) and 30% (six out of 20) of the mutant alleles in the 10 families studied were c.1190-1G > A and c.792+1G > T, respectively. The novel missense mutation p.R363H was transiently expressed in CHO cells, and showed retention of 2.3% IDUA activity. Neither p.W402X nor p.Q70X associated with the Hurler phenotype, or even p.R89Q associated with the Scheie phenotype, was found in this group. Finally, it was noted that the Chinese MPS I patients proved to be characterized with a unique set of IDUA gene mutations, not only entirely different from those encountered among Europeans and Americans, but also apparently not even the same as those found in other Asian countries.