http://repub.eur.nl/res/aut/31108/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/34218/ 2011-05-01T00:00:00Z The high frequency (3.3-3.9%) of acid α-glucosidase pseudodeficiency, c.[1726G > A; 2065G > A] homozygote (AA homozygote), in Asian populations complicates newborn screening for Pompe disease (glycogen storage disease type II or acid maltase deficiency) on dried blood spots, since AA homozygotes have a considerably low enzyme activity. We observed that hemoglobin in the enzyme reaction solution strongly interferes with the fluorescence of 4-methylumbelliferone released from 4-methylumbelliferyl α- d-glucopyranoside (4MU-αGlc) by acid α-glucosidase. Therefore, we have searched for a method to effectively eliminate hemoglobin in the reaction solution. Hemoglobin precipitation with barium hydroxide and zinc sulfate (Ba/Zn method) carried out after the enzyme reaction considerably enhances the fluorescence intensity while it does not reduce the intensity to any extent as can occur with conventional deproteinization agents like trichloroacetic acid. The Ba/Zn method greatly improved the separation between 18 Japanese patients with Pompe disease and 70 unaffected AA homozygotes in a population of Japanese newborns in the assay with 4MU-αGlc on dried blood spots. No overlap was observed between both groups. We further examined acid α-glucosidase activity in fibroblasts from 11 Japanese patients and 57 Japanese unaffected individuals including 31 c.[1726G; 2065G] homozygotes, 18 c.[1726G; 2065G]/[1726A; 2065A] heterozygotes and 8 AA homozygotes to confirm that fibroblasts can be used for definitive diagnosis. The patients were reliably distinguished from three control groups. These data provide advanced information for the development of a simple and reliable newborn screening program with dried blood spots for Pompe disease in Asian populations. http://repub.eur.nl/res/pub/28645/ 2010-01-01T00:00:00Z Enzyme replacement therapy for Pompe disease, a neuromuscular disorder characterized by lysosomal glycogen storage due to acid α-glucosidase deficiency, has entered the clinic. There is more than ever a need for early and reliable diagnosis. The objective of this review is to present a critical review of the recent literature on laboratory procedures to diagnose Pompe disease by enzymatic assay and DNA analysis. The methods we used were Compilation and expert interpretation of recent and relevant publications. The introduction of new and the updating of existing laboratory procedures have facilitated the diagnosis of Pompe disease (glycogen storage disease type II; acid maltase deficiency; OMIM 232300). With regard to enzymatic analysis, the application of acarbose as inhibitor of maltase-glucoamylase has enabled the use of mixed leukocyte preparations as diagnostic material. The use of glycogen as a natural substrate in the reaction mixture adds to the selectivity of this procedure. Newborn screening is envisaged and facilitated by the introduction of high-throughput procedures. DNA analysis has become an integral part of the diagnostic procedure for confirmation and completion, for carrier detection, and for genetic counseling. http://repub.eur.nl/res/pub/24532/ 2009-07-01T00:00:00Z To investigate the feasibility of newborn screening for glycogen storage disease type II (GSDII; Pompe disease or acid maltase deficiency) in the Japanese population, we assayed the acid α-glucosidase activity in dried blood spots from 715 Japanese newborns and 18 previously diagnosed patients using a fluorometric procedure. The enzyme activity of apparently healthy newborns showed a bimodal distribution. The median activity of the minor group (31 individuals, 4.3% of the samples) was 6.5 times lower than that of the major group. Four of the 715 control samples (0.56%) fell in the patient range. We then analyzed genomic DNA, extracted from the same blood spots, for the occurrence of two sequence variants, c.1726G>A and c.2065G>A, known to cause "pseudodeficiency". This analysis revealed that 27 of 28 individuals homozygous for c.[1726A; 2065A] belonged to the minor group. One c.[1726A; 2065A] homozygote had just slightly higher activity. Twelve of the 18 patients with GSDII either had one (9 cases) or two (3 cases) c.[1726A; 2065A] alleles. The frequency of this allele was double in the patient compared to the control group (0.42 vs 0.19) at the expense of a lower frequency of the c.[1726G; 2065G] and c.[1726G; 2065A] alleles (0.58 vs 0.71 and 0 vs 0.1). These findings illustrate that c.[1726A; 2065A] homozygosity among apparently healthy individuals (3.9 per 100) complicates newborn screening for GSDII in Japan, and further that one or more pathogenic mutations are associated with the c.[1726A; 2065A] allele. http://repub.eur.nl/res/pub/36712/ 2007-01-01T00:00:00Z Glycogen storage disease type II (GSDII; Pompe disease or acid maltase deficiency) is an autosomal recessive disorder caused by lysosomal acid α-glucosidase (AαGlu) deficiency and manifests predominantly as skeletal muscle weakness. Defects in post-translational modification and transport of mutant AαGlu species are frequently encountered and may potentially be corrected with chaperone-mediated therapy. In the present study, we have tested this hypothesis by using deoxynojirimycin and derivatives as chemical chaperones to correct the AαGlu deficiency in cultured fibroblasts from patients with GSDII. Four mutant phenotypes were chosen: Y455F/Y455F, P545L/P545L, 525del/R600C and D645E/R854X. In case of Y455F/Y455F and P545L/P545L, N-(n-butyl)deoxynojirimycin (NB-DNJ) restored the transport, maturation and activity of AαGlu in a dose dependent manner, while it had no effect on the reference enzyme β-hexosaminidase. NB-DNJ promoted export from the endoplasmic reticulum (ER) to the lysosomes and stabilized the activity of mutant AαGlu species, Y455F and P545L, inside the lysosomes. In long-term culture, the AαGlu activity in the fibroblasts from the patients with mutant phenotypes, Y455F/Y455F and P545L/P545L, increased up to 14.0- and 7.9-fold, respectively, in the presence of 10 μmol/L NB-DNJ. However, the effect of NB-DNJ on Y455F/Y455F subsided quickly after removal of the compound. We conclude that NB-DNJ acts in low concentration as chemical chaperone for certain mutant forms of AαGlu that are trapped in the ER, poorly transported or labile in the lysosomal environment. Chemical chaperone therapy could create new perspectives for therapeutic intervention in GSDII.