We prospectively studied the ocular features of patients with MPSI (Hurler/Hurler-Scheie/Scheie), MPSIV (Morquio) and MPSVI (Maroteaux-Lamy), to evaluate the effect of different therapeutic interventions and to correlate the findings with genetic and biomarker data.
We found that a Hurler syndrome fibroblast cell line heterozygous for the IDUA stop mutations Q70X and W402X showed a significant increase in alpha-L-iduronidase activity when cultured in the presence of gentamicin, resulting in the restoration of 2.8% of normal alpha-L-iduronidase activity.
We conducted molecular analysis for 60 MPS-affected patients [MPS I (n = 30) (Hurler syndrome = 17, Hurler-Scheie syndrome = 13), and MPS II (n = 30) (severe = 18, attenuated = 12)] and identified a total of 44 [MPS I (n = 22) and MPS II (n = 22)] different pathogenic variants comprising missense, nonsense, frameshift, gross deletions and splice site variants.
Using WES approach, we identified the definitive disease-causing mutations in four families: (i) a novel nonsense homozygous (c.1034C>G) in PHKG2 causing glycogen storage disease type 9C (GSD9C) in a male with initial diagnosis of GSD3; (ii) a novel homozygous 1-bp deletion (c.915del) in NSUN2 in a male proband with Noonan-like syndrome; (iii) a homozygous SNV (c.1598C>G) in exon 11 of IDUA causing Hurler syndrome in a female proband with unknown clinical diagnosis; (iv) a de novo known splicing mutation (c.1645+1G>A) in PHEX in a female proband with initial diagnosis of autosomal recessive hypophosphatemic rickets.
Transplantation did not produce measurable levels of either alpha-L-iduronidase (EC 3.2.1.76) in the leukocytes from patients with Hurler disease or of N-acetyl-alpha-D-glucosaminidase (EC 3.2.1.50) in the plasma of the patients with Sanfilippo B disease.
Together, these results support the predicted role of E182 and E299 in the catalytic mechanism of alpha-L-iduronidase and we propose that the mutation of either of these residues would contribute to a very severe clinical phenotype in a MPS I patient.
To investigate the plant lectin ricin B chain (RTB) as a novel carrier for enzyme delivery to the brain, an IDUA:RTB fusion protein (IDUAL), produced in N. benthamiana leaves, was tested in a murine model of Hurler syndrome (MPS I).
Though these children had the characteristic morphological features of the Hurler syndrome, enzyme assay of cultured fibroblasts showed normal levels of alpha-L-iduronidase and decreased activity of arylsulphatase B.
This study shows that pathology associated with MPSI can be prevented in the entire mouse brain by a single AAV vector injection, providing a preliminary evaluation of the feasibility of gene therapy to stop neuropathology in Hurler syndrome.
There was a threefold increase of glycosaminoglycans (GAG) in the brain of MPS-I, but only a slight increase in the MPS-V; GAG in the liver and spleen of all patients was noticeably increased. alpha-L-iduronidase activity was not detectable in the brain and liver of patients with MPS-I and MPS-V, thus suggesting a similar enzymatic defect.
The treatment of MPS I patient's fibroblasts homozygous for the p.Trp402<sup>∗</sup> mutation led to a significant increase in IDUA activity at 2, 15, and 30 days when compared to MPS I untreated fibroblasts.
The sustained expression of enzymatically active IDUA in multiple organs had a significant beneficial effect on the phenotypic abnormalities of MPS I, which may be translated to clinical gene therapy of patients with Hurler disease.
The purpose of this study was to assess the extent of the diagnostic delay in the two ultra-rare diseases, i.e., mucopolysaccharidosis I (MPS I) and III (MPS III), both of which are lysosomal storage disorders with different phenotypic severities (MPS 1 is characterized by the severe Hurler and the more attenuated non-Hurler phenotypes, MPS III is characterized by the severe rapidly progressing (RP) phenotype and more attenuated slowly progressing (SP) phenotype).
The premature stop codons Q70X and W402X are two of the most common alpha-l-iduronidase gene (IDUA) mutations accounting for up to 70% of MPS I disease alleles in some populations.