Carbon nanotubes as nanovectors for intracellular delivery of laronidase in Mucopolysaccharidosis type I

The immobilization of proteins on carbon nanotubes (CNTs) has been widely reported mainly for the preparation of sensors while the conjugation of enzymes for therapeutic purposes has scarcely been considered. Herein we report, to the best of our knowledge, the first example of intracellular delivery of a therapeutic enzyme by means of CNTs, retaining its activity. Mucopolysaccharidosis I is a rare genetic disease characterized by the deficiency or absence of the activity of the α-l-iduronidase (IDUA) enzyme. We evaluated the capacity of the recombinant form of the human IDUA enzyme, laronidase (Aldurazyme®), conjugated with CNTs to be internalized by fibroblasts from subjects affected with Mucopolysaccharidosis type I and the capacity of the enzyme to retain its activity after internalization. The enzyme was successfully delivered into the lysosomal space and the enzymatic activity of the conjugate was preserved after internalization up to 48 hours. This paves the way towards the use of such a kind of construct for therapeutic applications.

Mutation profile of theGAA gene in 40 Italian patients with late onset glycogen storage disease type II

Glycogen storage disease type II (GSDII) is a recessively inherited disorder due to the deficiency of acid alpha-glucosidase (GAA) that results in impaired glycogen degradation and its accumulation in the lysosomes. We report here the complete molecular analysis of the GAA gene performed on 40 Italian patients with late onset GSDII. Twelve novel alleles have been identified: missense mutations were functionally characterized by enzyme activity and protein processing in a human GAA-deficient cell line while splicing mutations were studied by RT-PCR and in silico analysis. A complex allele was also identified carrying three different alterations in cis. The c.-32-13T > G was the most frequent mutation, present as compound heterozygote in 85% of the patients (allele frequency 42.3%), as described in other late onset GSDII Caucasian populations. Interestingly, the c.-32-13T > G was associated with the c.2237G > A (p.W746X) in nine of the 40 patients. Genotype-phenotype correlations are discussed with particular emphasis on the subgroup carrying the c.-32-13T > G/c.2237G > A genotype.

Screening of 25 Italian patients with Niemann-Pick A reveals fourteen new mutations, one common and thirteen private, in SMPD1

Niemann-Pick disease (NPD) results from the deficiency of lysosomal acid sphingomyelinase (SMPD1). To date, out of more than 70-disease associated alleles only a few of them have a significant frequency in various ethnic groups. In contrast, the remainder of the mutations are rare or private. In this paper we report the molecular characterization of an Italian series consisting of twenty-five NPD patients with the severe neurodegenerative A phenotype. Mutation detection identified a total of nineteen different mutations, including 14 novel mutations and five previously reported lesions. The known p.P189fs and the novel p.T542fs were the most frequent mutations accounting for 34% and 18% of the alleles, respectively. Screening the alleles for the three common polymorphisms revealed the variant c.1516G>A (exon 6) and the repeat in exon 1, but not the variant c.965C>T (exon 2). In absence of frequent mutations, the prognostic value of genotyping is limited. However, new genotype/phenotype correlations were observed for this disorder that could in the future facilitate genetic counseling and guide selection of patients for therapy.

Acid sphingomyelinase: identification of nine novel mutations among Italian Niemann Pick type B patients and characterization of in vivo functional in-frame start codon

Niemann Pick disease (NPD) is an autosomal recessive disorder due to the deficit of lysosomal acid sphingomyelinase, which results in intracellular accumulation of sphingomyelin. In the present work we studied 18 patients with NPD type B, including five individuals who presented an intermediate phenotype characterised by different levels of neurological involvement. We identified nine novel mutations in the SMPD1 gene including six single base changes c.2T>G, c.96G>A, c.308T>C, c.674T>C, c.732G>C, c.841G>A (p.M1_W32del, p.W32X, p.L103P, p.L225P, p.W244C, p.A281T) and three frameshift mutations c.100delC, c.565dupC, c.575dupC (p.G34fsX42, p.P189fsX1 and p.P192fsX14). The novel c.2T>G (p.M1_W32del) mutation inactivates the first in-frame translation start site of the SMPD1 gene and in the homozygous status causes NPD type B indicating that in'vivo translation of wild type SMPD1 initiates from the first in-frame ATG. Moreover, the new c.96G>A (p.W32X) introduces a premature stop codon before the second in-frame ATG. As a consequence of either c.2T>G (p.M1_W32del) or c.96G>A (p.W32X), impaired translation from the first in-frame ATG results in a mild NPD-B phenotype instead of the severe phenotype expected for a complete deficiency of the enzyme, suggesting that when the first ATG is not functional, the second initiation codon (ATG33) still produces a fairly functional sphingomyelinase. Analysis of the patients'clinical and molecular data demonstrated that all five patients with the intermediate phenotype carried at least one severe mutation. No association between the onset of pulmonary symptoms and genotype was observed. Finally, the presence of c.96G>A (p.W32X), the most frequent allele among Italian NPD type B population, and c.1799G>C (p.R600P) as compound heterozygotes in association with severe mutations suggested a beneficial effect for both mutations.

Prenatal diagnosis of Pelizaeus-Merzbacher disease: detection of proteolipid protein gene duplication by quantitative fluorescent multiplex PCR

A prenatal diagnosis of Pelizaeus-Merzbacher disease (PMD) resulting from proteolipid protein gene (PLP) duplication was performed by a quantitative fluorescent multiplex PCR method. PLP gene copy number was determined in the proband, the pregnant mother, the male fetus and two aunts. Small amounts of genomic DNA extracted from peripheral blood and from chorionic villi were used. The fetus, in common with the proband, was identified as PMD-affected being a carrier of the PLP gene duplication, inherited from the mother, while the two aunts were non-carriers. The data obtained were confirmed by segregation analysis of a PLP-associated dinucleotide-repeat polymorphism amplified by the same multiplex PCR.

Aberrant splicing at catalytic site as cause of infantile onset glycogen storage disease type II (GSDII): molecular identification of a novel IVS9 (+2GT-->GC) in combination with rare IVS10 (+1GT-->CT)

Glycogen storage disease type II (GSDII) results from deleterious mutations in acid alpha-glucosidase gene. To date several mutant alleles have been studied including missense and nonsense mutations, insertions, small and large deletions as well as splice site mutations. Apart from IVS1 (- 13-->G), 525delT, and Delta18, the other mutations are rare and often unique to single patients. Moreover, the molecular findings also observed in the different ethnic groups makes it difficult to attempt to correlate genotype and phenotype to explain the origin of clinical variability. Even though there are no conclusive genotype phenotype correlations, the in frame splice site mutations identified up until now have been found associated with the juvenile/adult onset of GSDII. In this study we describe a novel in frame splicing defect, IVS9 (+2GT-->GC), identified in combination with the rare IVS10 (+1GT-->CT) mutation in a patient with classic infantile GSDII disease. Because both mutations occur at the catalytic site region, it is likely that the alteration of both catalytic function and steric conformation of the enzyme may be responsible for the most severe form of the disease.

Four year follow-up of a case of fucosidosis treated with unrelated donor bone marrow transplantation

Fucosidosis is a rare autosomal recessive lysosomal disorder caused by alpha-fucosidase deficiency. We report a child with fucosidosis, second daughter of non-consanguineous parents, for whom biochemical diagnosis followed clinical evidence of the disease in her older sister. Based on previous experiences, the indication to transplant was considered. Since she lacked a matched sibling, an unrelated marrow donor was found. At pre-hematopoietic stem cell transplantation evaluation, first signs of neurological involvement were clinically detectable. MRI showed diffuse hypomyelination and auditory brainstem responses and somatic-sensorial evoked potentials were altered. Visual evoked potentials were normal, tortuosity in the retinal veins and peripapillary hemorrhages were detected. Bone marrow transplantation conditioning was with a regimen of busulphan, thiotepa and cyclophosphamide; in vivo Campath 1G, cyclosporin A and short course methotrexate were given to prevent graft-versus-host disease. The patient engrafted rapidly and her post-transplant course was complicated by moderate graft-versus-host disease, transient episodes of idiopathic thrombocytopenic purpura, repeated septic complications and recurrent episodes of Sweet's syndrome. Sequential short tandem repeat polymorphisms on peripheral blood and bone marrow cells documented the persistence of donor engraftment. Follow-up showed a progressive rise of enzymatic levels. Psychomotor development improved, as confirmed by evaluation of evoked potentials and by MRI scanning.

Evidence for a founder effect in Sicilian patients with glycogen storage disease type II

Glycogen storage disease type II (GSD II) is an autosomal recessive inherited disorder due to the deficiency of the enzyme acid alpha-glucosidase, which causes an accumulation of glycogen in lysosomes. The deletion of exon 18 (delta 18) is a frequent mutation associated with a severe phenotype. We analyzed 25 Italian patients, 5 of whom were found to be delta 18 carriers. All these 5 patients came from Catania, a town in Sicily. We report on the analysis of 5 intragenic single-point polymorphic markers in the delta 18 patients and on the subsequent characterization of a delta 18-associated haplotype. The frequency of this haplotype in GSD II patients and normal individuals was 1 and 0.196, respectively (chi(2) = 20.9; p < 0.001). The high frequency of the delta 18 allele in this Italian subpopulation is likely to be due to a founder effect.

Mutations in the glucose-6-phosphatase gene of 53 Italian patients with glycogen storage disease type Ia

Type Ia glycogen storage disease (GSD1a) is an autosomal recessive metabolic disorder caused by a deficiency in glucose-6-phosphatase (G6Pase). Recent cloning of the G6Pase gene and the subsequent identification of several disease-causing mutations have shown an ethnic molecular heterogeneity. Using SSCP analysis and DNA sequencing, we characterized the G6Pase gene of 53 unrelated Italian patients. The two most common mutations, R83C and Q347X, accounted for 66.9% of the mutant alleles. Eight novel mutations and three rare mutations were identified in 15.7% of disease alleles. These results suggest that a DNA-based method can be used as an initial screening in Italian patients clinically suspected of having GSD1a, avoiding liver biopsy for enzymatic diagnosis. In particular, a noninvasive diagnosis is a suitable method for the Italian subpopulation coming from Sicily, where the R83C mutation is present in 80% of mutant alleles. Molecular carrier detection and prenatal diagnosis can be provided to GSD1a families with identified mutation in the propositus.

A 9-bp deletion (2320del9) on the background of the arylsulfatase A pseudodeficiency allele in a metachromatic leukodystrophy patient and in a patient with nonprogressive neurological symptoms

A 9-bp deletion (2320del9) was detected in the arylsulfatase A genes of a patient with late infantile metachromatic leukodystrophy and of a patient with nonprogressive neurological symptoms and very low arylsulfatase A activity. Both patients are heterozygous for the deletion, which involves codons 406-408 and causes loss of a Ser-Asp-Thr tract in the predicted protein. In both patients the 9-bp deletion lies in a pseudodeficiency allele. The patient with metachromatic leukodystrophy carries the common 459 + 1G > A mutation in the other allele. The other patient is homozygous for the pseudodeficiency allele, and consequently is a compound heterozygote for a metachromatic leukodystrophy allele and a pseudodeficiency allele. We hypothesize that the compound heterozygosity predisposes to the development of nonprogressive neurological symptoms in the presence of additional, still unknown, genetic or nongenetic factors.

A T > C transition causing a Leu > Pro substitution in a conserved region of the arylsulfatase A gene in a late infantile metachromatic leukodystrophy patient

A T > C transition (L428P) was detected in the arylsulfatase A alleles of a late infantile metachromatic leukodystrophy patient. The mutation causes a Leu > Pro substitution in exon 8. It lies in a region conserved among arylsulfatases. The mutation was not detected in 37 other patients and in 57 normal controls.

Molecular analysis of the arylsulphatase A gene in late infantile metachromatic leucodystrophy patients and healthy subjects from Italy

A molecular analysis of the arylsulphatase A gene was performed on 26 unrelated, Italian, late infantile metachromatic leucodystrophy patients. The frequency of the common disease causing mutations 609A and 2381T was 28.8% and 1.9% respectively. Pseudodeficiency allele frequency in patients was found to be 13.5% and a frequency of 10.1% was found in 89 unaffected normal controls. The frequency of the 609A mutation in Italian late infantile patients is lower than in late infantile patients from northern Europe, suggesting a higher frequency of different sporadic mutations in the Italian population. A cooperative in cis effect in phenotype determination involving arylsulphatase A mutations and the eventual background of the pseudodeficiency allele is proposed.