Genotype-phenotype correlation in 44 Czech, Slovak, Croatian and Serbian patients with mucopolysaccharidosis type II.

Mucopolysaccharidosis type II (Hunter syndrome, MPS II, OMIM 309900) is an X-linked lysosomal storage disorder caused by deficiency of iduronate-2-sulfatase (IDS). We analyzed clinical and laboratory data from 44 Slavic patients with this disease. In total, 21 Czech, 7 Slovak, 9 Croatian and 7 Serbian patients (43 M/1 F) were included in the study (median age 11.0 years, range 1.2-43 years). Birth prevalence ranged from 1:69,223 (Serbia) to 1:192,626 (Czech Rep.). In the majority of patients (71%), the disease manifested in infancy. Cognitive functions were normal in 10 patients. Four, six and 24 patients had mild, moderate, and severe developmental delay, respectively, typically subsequent to developmental regression (59%). Residual enzyme activity showed no predictive value, and estimation of glycosaminoglycans (GAGs) had only limited importance for prognosis. Mutation analysis performed in 36 families led to the identification of 12 novel mutations, eight of which were small deletions/insertions. Large deletions/rearrangements and all but one small deletion/insertion led to a severe phenotype. This genotype-phenotype correlation was also identified in six cases with recurrent missense mutations. Based on patient genotype, the severity of the disease may be predicted with high probability in approximately half of MPS II patients.

X-Chromosome Inactivation Analysis in Different Cell Types and Induced Pluripotent Stem Cells Elucidates the Disease Mechanism in a Rare Case of Mucopolysaccharidosis Type II in a Female.

Mucopolysaccharidosis type II (MPS II) is an X-linked lysosomal storage disorder resulting from deficiency of iduronate-2-sulphatase activity. The disease manifests almost exclusively in males; only 16 symptomatic heterozygote girls have been reported so far. We describe the results of X-chromosome inactivation analysis in a 5-year-old girl with clinically severe disease and heterozygous mutation p.Arg468Gln in the IDS gene. X inactivation analysed at three X-chromosome loci showed extreme skewing (96/4 to 99/1) in two patient's cell types. This finding correlated with exclusive expression of the mutated allele. Induced pluripotent stem cells (iPSC) generated from the patient's peripheral blood demonstrated characteristic pluripotency markers, deficiency of enzyme activity, and mutation in the IDS gene. These cells were capable of differentiation into other cell types (cardiomyocytes, neurons). In MPS II iPSC clones, the X inactivation ratio remained highly skewed in culture conditions that led to partial X inactivation reset in Fabry disease iPSC clones. Our data, in accordance with the literature, suggest that extremely skewed X inactivation favouring the mutated allele is a crucial condition for manifestation of MPS II in females. This suggests that the X inactivation status and enzyme activity have a prognostic value and should be used to evaluate MPS II in females. For the first time, we show generation of iPSC from a symptomatic MPS II female patient that can serve as a cellular model for further research of the pathogenesis and treatment of this disease.

Ornithine carbamoyltransferase deficiency: molecular characterization of 29 families.

Ornithine carbamoyltransferase deficiency is the most common inherited defect of the urea cycle. We examined 28 male and 9 female patients from 29 families and identified 25 distinct mutations in OTC, 14 of which were novel. Three novel missense mutations (p.Ala102Pro, p.Pro158Ser, p.Lys210Glu) and a novel deletion of the Leu43 are not directly involved either in the enzyme active site or in the intersubunit interactions; however, the mutations include conserved residues involved in intramolecular interaction network essential for the function of the enzyme. Three novel large deletions - a 444 kb deletion affecting RPGR, OTC and TSPAN7, a 10 kb-deletion encompassing OTC exons 5 and 6 and a 24.5 kb-deletion encompassing OTC exons 9 and 10 - have probably been initiated by double strand breaks at recombination-promoting motifs with subsequent non-homologous end joining repair. Finally, we present a manifesting heterozygote carrying a hypomorphic mutation p.Arg129His in combination with unfavorably skewed X-inactivation in three peripheral tissues.

Eight novel ABCD1 gene mutations and three polymorphisms in patients with X-linked adrenoleukodystrophy: The first polymorphism causing an amino acid exchange.

X-ALD is a neurological disorder associated with inherited defects in the ABCD1 (ALD) gene located on Xq28 and with impaired peroxisomal very long-chain fatty acid beta-oxidation. We examined the ABCD1 gene in probands from 11 unrelated X-ALD Czech and Slovak families by the direct sequencing of cDNA or genomic PCR products. In 10 families there were 10 different mutations, eight of which were novel. The spectrum of mutations consists of six point mutations, three microdeletions (1bp, 2bp, 4 bp), and one large deletion (229bp). In the 11th family we detected two novel single-base pair substitutions in exon 1 (c.38 A>C and c.649 A>G), both causing amino acid exchanges (N13T and K217E). Expression studies revealed that only K217E is a deleterious mutation, because a plasmid encoding ALDP with K217E was ineffective in the restoration of defective beta-oxidation in X-ALD fibroblasts. The N13T amino acid exchange, on the other hand, did not affect ALDP function. Thus, N13T represents the first polymorphism causing an amino acid exchange in the ABCD1 gene. As this polymorphism was observed neither in 100 control alleles nor in 300 X-ALD patients who have been sequenced so far world-wide, it seems to be very rare or unique. Two additional novel polymorphisms were found by the sequencing of the ABCD1 gene from our patients: c.-59 C/T in the 5'untranslated region and c.2019 C/T (F673F) in exon 10. The frequencies of these two polymorphisms, were 11/150 and 2/150 control alleles, respectively.