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.

Natural history of the respiratory involvement in Anderson-Fabry disease.

BACKGROUND: Anderson-Fabry disease (AFD) is an X-linked disorder caused by deficient activity of enzyme alpha-galactosidase A, resulting in the accumulation of glycosphingolipids within lysosomes. Pulmonary involvement in AFD has previously been documented, but until now has been studied only in a few series of patients without any longitudinal follow-up. The aim of this study was to compare spirometric changes in AFD patients with a matched control population and to follow the subsequent progression of the disease. MATERIALS AND METHODS: Fifty individuals (27 women, 23 men, mean age 40 +/- 14 years) with AFD from 14 families underwent a static spirometric examination under standard conditions. A set of indices was compared with that of the control population. Out of this cohort, 39 individuals not receiving enzyme replacement therapy were longitudinally evaluated (median follow-up time 24 months). RESULTS: A clinically significant reduction in spirometric parameters, corresponding to mild to severe airway obstruction, was observed in 26% of women and 61% of men. During the serial follow-up, a significant (p < 0.05) age-dependent reduction of predicted %FVC and %FEV1 values was observed in male patients, while the influence of age was not seen in female patients. The %FEF(25-75) values decreased by similar degrees in men and women and in older and younger patients, indicating that progressive bronchial disease affects the small airways first. CONCLUSIONS: We have demonstrated a clinically relevant age- and sex-dependent progressive pulmonary involvement in AFD patients. The effects of enzyme replacement therapy on pulmonary involvement remain to be demonstrated.