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.

Origin and spread of a common deletion causing mucolipidosis type II: insights from patterns of haplotypic diversity

Mucolipidosis II (ML II alpha/beta), or I-cell disease, is a rare genetic disease in which activity of the uridine diphosphate (UDP)-N-acetylglucosamine:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-phosphotransferase) is absent. GlcNAc-phosphotransferase is a multimeric enzyme encoded by two genes, GNPTAB and GNPTG. A spectrum of mutations in GNPTAB has been recently reported to cause ML II alpha/beta. Most of these mutations were found to be private or rare. However, the mutation c.3503_3504delTC has been detected among Israeli and Palestinian Arab-Muslim, Turkish, Canadian, Italian, Portuguese, Irish traveller and US patients. We analysed 44 patients who were either homozygous or compound heterozygous for this deletion (22 Italians, 8 Arab-Muslims, 1 Turk, 3 Argentineans, 3 Brazilians, 2 Irish travellers and 5 Portuguese) and 16 carriers (15 Canadians and 1 Italian) for three intragenic polymorphisms: c.-41_-39delGGC, c.18G>A and c.1932A>G as well as two microsatellite markers flanking the GNPTAB gene (D12S1607 and D12S1727). We identified a common haplotype in all chromosomes bearing the c.3503_3504delTC mutation. In summary, we showed that patients carrying the c.3503_3504delTC deletion presented with a common haplotype, which implies a common origin of this mutation. Additionally, the level of diversity observed at the most distant locus indicates that the mutation is relatively ancient (around 2063 years old), and the geographical distribution further suggests that it probably arose in a peri-Mediterranean region.

Enhancing cranial nerves and cauda equina: an emerging magnetic resonance imaging pattern in metachromatic leukodystrophy and krabbe disease

We report on three cases of infantile Krabbe disease and one case of infantile metachromatic leukodystrophy showing magnetic resonance (MR) imaging findings of diffuse and coexistent cranial nerve and cauda equina nerve roots enhancement. Such findings may be simultaneous, or even precede, typical white matter abnormalities and, in the appropriate clinical context, may facilitate an earlier diagnosis. There is a rational for the use of contrast agents and craniospinal MR imaging during the first imaging of children with a history of psychomotor regression and clinical evidence of peripheral nerve involvement to exclude differential diagnoses.

Type II sialidosis: review of the clinical spectrum and identification of a new splicing defect with chitotriosidase assessment in two patients

Sialidosis is a lysosomal storage disease caused by the deficiency of alpha-N-acetyl neuraminidase-1 (NEU1). Sialidosis is classified into two main clinical variants: Type I, the milder form of the disease, and Type II, which can in turn be subdivided into three forms: congenital, infantile and juvenile. We report herein the clinical, biochemical and molecular characterisation of two patients with Type II sialidosis exhibiting the congenital (P1) and infantile forms (P2). We also review clinical data on the rare Type II forms of sialidosis in the hope of improving understanding of the disorder and facilitating its diagnosis. The genetic characterization of the two patients showed one known [c. 679G > A (p.G227R)] NEU1 missense mutation (detected in P2), and the new c.807 + 1G > A splicing defect (detected in P1), a genetic lesion that is extremely rare in this disease. Interestingly, P2 presented an extremely elevated level of chitotriosidase in plasma. This is the first pathological detection of chitotriosidase in sialidosis patients.

An Alu insertion in compound heterozygosity with a microduplication in GNPTAB gene underlies Mucolipidosis II

Mucolipidosis type II (ML II) is a fatal, autosomal recessive, lysosomal storage disorder characterized by severe clinical and radiologic features. ML II results from mutations in alpha and beta subunits, encoded by the GlcNAc-1-phosphotransferase gene (GNPTAB). Most of the 40 different GNPTAB mutations reported so far are insertions and deletions predicting diverse types of aberrant proteins. Alu mobile elements have however never been involved in these events up to now. The Italian ML II patient of our study showed an Alu retrotrasposition in GNPTAB exon 5. The Alu insertion mutation (NM_024312.3:c.555_556insHSU14569) generated a transcript with a skipping of the target exon 5 and a frameshift p.S122fs, causing a premature translation termination codon at position 123. This insertion mutation was found in compound heterozygosity with the frameshift p.S887KfsX33, resulting from a new mono-nucleotide duplication (c.2659dupA) that occurred in GNPTAB exon 13. A possible involvement of cis-splicing elements having an exonic location, such as exon enhancers (ESEs), is discussed as mechanism that led to the production of the aberrant mRNA splicing.

GFAP mutations and polymorphisms in 13 unrelated Italian patients affected by Alexander disease

Alexander disease (AD), a rare neurodegenerative disorder of the central nervous system, is characterized by the accumulation of cytoplasmic protein aggregates (Rosenthal fibers) composed of glial fibrillary acidic protein (GFAP) and small heat-shock proteins within astrocytes. To date, more than 40 different GFAP mutations have been reported in AD. The present study is aimed at the molecular diagnosis of Italian patients suspected to be affected by AD. By analyzing the GFAP gene of 13 unrelated patients (eight with infantile form, two with juvenile form and three with adult form), we found 11 different alleles, including four new ones. Among the novel mutations, three (p.R70Q, p.R73K, and p.R79P) were identified in exon 1 and p.L359P in exon 6. The sequence analysis also detected six different single nucleotide polymorphic variants, including two previously unreported ones, spread throughout non-coding regions (introns 2, 3, 5, 6, and 3'UTR) of the gene. All patients were heterozygous for the mutations, thus confirming their dominant effect.

Movement and mood disorder in two brothers with Gaucher disease

Gaucher disease (GD) is a lysosomal storage disorder with a wide spectrum of phenotypic presentations. We report the case histories of two adult brothers with GD who developed both parkinsonism and psychiatric symptoms. Direct sequencing and real-time polymerase chain reaction were used to establish that the patients were homozygous for mutation L444P. While parkinsonism has been described previously in GD, these patients had atypical features, including a complicated mood disorder. The comorbidity of GD and a mood disorder is a new finding, as psychiatric manifestations of GD have been described rarely. The etiology of the mental illness could be related to the processes contributing to the development of parkinsonism.

Molecular genetics of late onset glycogen storage disease II in Italy

Glycogen Storage Disease Type II (GSDII) is a recessively inherited disorder due to the deficiency of acid alpha-glucosidase (GAA) that results in glycogen accumulation in the lysosomes. The molecular analysis of the GAA gene was performed on 45 Italian patients with late onset GSDII. DHPLC analysis revealed 28 polymorphisms spread all over the GAA gene. Direct sequencing identified the 96% of the mutant alleles, 12 of which are novel. 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. All the patients studied carried a severe mutation in combination with a milder one, which explains the late onset of the disease. The c.-32-13T > G was the most frequent mutation, present as compound heterozygote in 85% of the patients as described in other late onset GSDII Caucasian populations. Interestingly, 10 of the 45 patients carried the c.-32-13T > G associated to the severe c.2237G > A (p.W746X) mutation. However, despite the common genotype, patients presented with a wide variability in residual enzyme activity, age of appearance of clinical signs and rate of disease progression, suggesting that other genetic/environment factors may modulate clinical presentation.

Funtional characterization of four novel MAN2B1 mutations causing juvenile onset alpha-mannosidosis

Alpha-mannosidosis is a recessively inherited disorder due to the deficiency of the lysosomal alpha-mannosidase. We report the molecular analysis performed in two patients with the late onset form of alpha-mannosidosis. Four new alleles were identified: three missense mutations involving highly conserved residues, c.597 C>A (p.H200N), c.1553 T>C (p.L518P) and c.2746 C>A (p.R916S) and a single nucleotide deletion, c.2660delC. In vitro expression studies in COS-1 cells demonstrated that pH200N, p.L518P and p.R916S proteins are expressed but retained no residual enzyme activity. These data are supported by structural 3D analysis which predicted that both p.L518P and p.R916S could affect the interaction of the small E-domain with the active site domain or the main body of the structure while the pH200N might alter substrate binding or other catalytic properties. Finally, the c.2660delC causes a frameshift introducing a premature stop codon (p.T887SfsX45), presuming to be a severe mutation.

Hepatic and neuromuscular forms of glycogenosis type III: nine mutations in AGL

Glycogenosis type III (Cori disease) is an autosomal recessive disorder caused by the deficiency of the glycogen debranching enzyme, encoded by the AGL gene, and existing in six isoforms alternately spliced in a tissue-specific way. Generally, disease onset occurs early on starting from the first year of life, with hepatomegaly, hypoglycemia, hyperlipidemia, increased CK levels, and, in some cases, short stature and slight mental retardation. Frequently, hepatomegaly tends to resolve spontaneously and inexplicably during childhood, when myopathy, often associated with cardiomyopathy, arises. This disease is known to lack almost invariably clear links between the genotype and clinical phenotype. We describe nine new mutations in Italian patients: four nonsense (p.Arg285X, p.Lys422X, p.Arg910X, p.Arg977X), three frameshift (c.442delA, c.753_756delGACA, c.3963delG), and two missense (p.Ala1120Pro, p.Arg524His). Particularly, the nonsense p.Arg285X is linked to an exonic splicing enhancer and it was found to produce two species of transcripts at the same time. Moreover, we discuss a subgroup of subjects carrying c.2681+1G>A, which has proven to be the most frequent mutation among our patients. The previously described c.664+3A>G was also detected in two patients, both homozygous. The present work is yet another confirmation that the individual genetic background plays a pivotal role in influencing the phenotypes, as occurs in other metabolic diseases.

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.

Homozygosity for the p.K136E mutation in the SLC17A5 gene as cause of an Italian severe Salla disease

Lysosomal free sialic acid storage diseases are recessively inherited allelic neurodegenerative disorders that include Salla disease (SD) and infantile sialic acid storage disease (ISSD) caused by mutations in the SLC17A5 gene encoding for a lysosomal membrane protein, sialin, transporting sialic acid from lysosomes. The classical form of SD, enriched in the Finnish population, is related to the p.R39C designed Salla(FIN) founder mutation. A more severe phenotype is due both to compound heterozygosity for the p.R39C mutation and to different mutations. The p.R39C has not been reported in ISSD. We identified the first case of SD caused by the homozygosity for p.K136E (c.406A>G) mutation, showing a severe clinical picture, as demonstrated by the early age at onset, the degree of motor retardation, the occurrence of peripheral nerve involvement, as well as cerebral hypomyelination. Recently, in vitro functional studies have shown that the p.K136E mutant produces a mislocalization and a reduced activity of the intracellular sialin. We discuss the in vivo phenotypic consequence of the p.K136E in relation to the results obtained by the in vitro functional characterization of the p.K136E mutant. The severity of the clinical picture, in comparison with the classical SD, may be explained by the fact that the p.K136E mutation mislocalizes the protein to a greater degree than p.R39C. On the other hand, the presence of a residual transport activity may account for the absence of hepatosplenomegaly, dysostosis multiplex, and early lethality typical of ISSD and related to the abolished transport activity found in this latter form.

Different molecular mechanisms leading to white matter hypomyelination in infantile onset lysosomal disorders

Hypomyelinating leukoencephalopathies may be related to a primary disturbance in the formation of myelin or may be caused by neuronal, oligodendrocytic or astrocytic dysfunction, leading to a failure of myelination. Abnormal myelination related to a direct metabolic damage on oligodendrocytes has been shown to occur in some animal models of lysosomal storage diseases. To demonstrate that cerebral white matter hypomyelination may occur also in humans affected by early-onset lysosomal storage diseases, we report three cases with infantile-onset lysosomal storage disorders (type 1 GM1 gangliosidosis, globoid cell leukodystrophy or Krabbe's disease, and type A Niemann-Pick disease) showing white matter hypomyelination. Hypomyelinating leukoencephalopathy may therefore represent a feature of lysosomal storage disorders with onset in the first months of life, when the process of myelination is particularly active, indicating that neuronal storage disorders may be primarily responsible for central nervous system hypomyelination.

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.

Clinical and molecular findings in patients with giant axonal neuropathy (GAN)

Giant axonal neuropathy (GAN) is a rare autosomal recessive neurodegenerative disorder of early onset, clinically characterized by a progressive involvement of both peripheral and CNS. The diagnosis is based on the presence of characteristic giant axons, filled with neurofilaments, on nerve biopsy. Recently, the defective protein, gigaxonin, has been identified and different pathogenic mutations in the gigaxonin gene have been reported as the underlying genetic defect. Gigaxonin, a member of the BTB/kelch superfamily proteins, seems to play a crucial role in the cross talk between the intermediate filaments and the membrane network. The authors report clinical and molecular findings in five Italian patients with GAN. This study shows the allelic heterogeneity of GAN and expands the spectrum of mutations in the GAN gene. The frequent occurrence of private mutations stresses the importance of a complete gene analysis.

Mutational analysis of the AGL gene: five novel mutations in GSD III patients

Total or partial lack of glycogen debranching enzyme (GDE or AGL, amylo-1,6-glucosidase, 4-alpha-glucanotransferase) is responsible for Glycogen Storage Disease type III (GSDIII), a rare autosomal recessive disorder of glycogen metabolism. The clinical and biochemical features of GSDIII subjects are quite heterogeneous, and this mirrors the genotype-phenotype heterogeneity among patients. In this paper, we report the molecular characterisation of five unrelated subjects, four Italian and one Tunisian. The following new mutations are described and confirm the genetic heterogeneity of this disease: p.R864X, p.R428K, c.3911 insA, p.G1087R and c.3512_3549dup+c.3512_3519del. The functional relevance of these mutations is discussed on the basis of the recently acquired knowledge about the boundaries and structures of the two catalytic domains.

Molecular analysis of 30 mucopolysaccharidosis type I patients: evaluation of the mutational spectrum in Italian population and identification of 13 novel mutations

Mucopolysaccharidosis type I (MPS-I orMPS1) is an autosomal recessive condition characterized by a broad range of clinical symptoms. Molecular diagnosis of MPS-I is important for analyzing genotype-phenotype correlation and for selecting patients for innovative therapies. In this study we analyzed 30 Italian MPS-I patients with different phenotypes (20 severe, 6 intermediate, 4 mild) in an attempt to recognize the mutational spectrum in our population and to identify major DNA alterations specific to our country. We identified 93% of mutated alleles (56 out of 60) with the reconstruction of the complete genotype in 26 patients out of 30. Twenty-three different mutations were found, 13 of which are novel while the remaining 10 have been already described. Among the novel mutations we found 5 non conservative missense mutations (A160D, E178K, P183R, G197D, D349Y), one nonsense mutation (C53X), 6 deletions (468-470del3, 486-491del6, 755-759del5, 1251delC, 1839-1867del29, 1902-1903del2), and one splice site mutation (IVS11+5G>A). No common mutation for MPS-I is present in our country. Frequently (40% of the alleles), mutations were found in just one or two patients. However, Q70X, P533R, G51D, and W402X mutations were present in several patients (15%, 13.3%, 13.3%, and 11.6% of the alleles respectively) suggesting a Mediterranean origin of the P533R and G51D mutations. In most cases the patients' genotypes were unique combinations of mutations. The great heterogeneity found in our MPS-I population hampers mutation detection and hinders the genotype-phenotype correlation.

The effect of four mutations on the expression of iduronate-2-sulfatase in mucopolysaccharidosis type II

Mucopolysaccharidosis type II (Hunter syndrome; OMIM 309900) is a rare X-linked recessive lysosomal storage disorder caused by the deficiency of the enzyme iduronate-2-sulfatase (IDS; EC 3.1.6.13). Different alterations at the IDS locus, mostly missense mutations, have been demonstrated, by expression study, as deleterious, causing significant consequences on the enzyme function or stability. In the present study we report on the results of the transient expression of the novel K347T, 533delTT, N265I and the already described 473delTCC (previously named DeltaS117) mutations in the COS 7 cells proving their functional consequence on IDS activity. This type of information is potentially useful for genotype-phenotype correlation, prognosis and possible therapeutic intervention.

Molecular analysis of 40 Italian patients with mucopolysaccharidosis type II: New mutations in the iduronate-2-sulfatase (IDS) gene

Mucopolysaccharidosis type II (MPS2, or Hunter syndrome), rare X-linked lysosomal storage disorder, results from deleterious mutations in the iduronate-2-sulfatase (IDS) gene. We report here the mutational analysis of a total of 40 unrelated Italian MPS II patients ranging from mild to severe phenotype. We are able to assign the genotype to 29 of them (72.5%), identifying 22 different mutations, five of which are unpublished (c.533delTT, W12X, N265I, c.1131-1142del, c.1131-1305del). A total of 55.2% of the molecularly characterised patients resulted from missense mutations, 20.7% from nonsense mutations, and another 13.8% of patients from small deletions (<20pb) or splice mutations, whereas 10.3% of the cases carried major structural alterations such as large deletion and rearrangements. The results reported here support the evidence of the mutational heterogeneity of the IDS gene as well as the difficulty to correlate genotype and phenotype in the patients with MPSII. However, the molecular characterisation of the patients is advantageous, making the carrier detection feasible for the females in the family at risk and improving the reliability of prenatal diagnosis techniques. Moreover, it provides a good foundation for therapeutic strategies.

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.

Molecular defects in the alpha-N-acetylglucosaminidase gene in Italian Sanfilippo type B patients

Sanfilippo syndrome type B (mucopolysaccharidosis IIIB) is a rare autosomal recessive disorder characterized by the inability to degrade heparan sulfate because of a deficiency of the lysosomal enzyme alpha-N-acetylglucosaminidase (NAGLU). We performed mutation screening in a group of 20 patients, identyifing 28 mutations, 14 of which were novel (L35F, 204delC, 221insGCGCG, G82D, W156C, 507delC, IVS3+1G-->A, E336X, V501G, R520W, S534Y, W649C, 1953insGCCA, 2185delAGA). Four of these mutations were found in homozygosity and only one was seen in two different patients, showing the remarkable molecular heterogeneity of the disease. Mutation IVS3+1G-->A produces aberrant RNA splicing: it represents a base substitution from G to A of the invariant GT dinucleotides at the splicing donor site of intron 3 resulting in the skipping of exon 3 and both exons 2 and 3. Transient transfection of COS cells, by DNA mutagenized with NAGLU mutations, produced enzymatic molecules without activity, demonstrating the deleterious nature of the defects. Metabolic labeling of transfected mutants suggested a normal synthesis of the involved polypeptide for missense alterations, whereas increased protein or mRNA instability was shown for nonsense and most of the frameshift mutations.

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.

Identification of a novel recombinant allele in three unrelated Italian Gaucher patients: implications for prognosis and genetic counseling

Gaucher disease (GD) results from deleterious mutations in the glucocerebrosidase gene. The relatively high frequency of some of these, especially at cDNA nucleotide 1226G (N370S) and at cDNA nucleotide 1448C (L444P), has led to the development of rapid screening techniques that can sometimes be misleading. In this report, we describe a novel rearrangement between the glucocerebrosidase gene and its pseudogene, identified as a consequence of a discrepancy between the genotype, homozygous for the common 1226G mutation, of an Italian patient with type 1 Gaucher disease, and the absence of the 1226G allele in her daughter. Additional investigations went on to reveal a novel recombinant allele beginning in intron 6 and extending through the rest of the coding sequence. Italian GD patients found homozygous for a specific mutation or with one or both alleles still unknown were further investigated and the novel recombinant allele was identified in an adult type 1 patient previously genotyped 1226G/1226G and in a young patient with an unknown genotype. The detection of this allele in three unrelated GD patients originating from the same geographic area in central Italy suggested a founder effect. This study emphasizes the implications of an accurate genotyping for the prognostic value of glucocerebrosidase genotype and reliable genetic counseling.

Functional characterization of the novel mutation IVS 8 (-11delC) (-14T>A) in the intron 8 of the glucocerebrosidase gene of two Italian siblings with Gaucher disease type I

Gaucher disease, the most common glycolipid storage disease, can be caused by a large variety of mutations. We report here the identification and characterization of a novel mutation in the human glucocerebrosidase gene, IVS 8 (-11delC) (-14T>A), in two siblings with Gaucher disease type I which occurs within the 3' end of intron 8. Both siblings were compound heterozygotes for the IVS 8 (-11delC) (-14T>A) mutation and for the c.626 G>C (R170P) substitution within exon 6. No mRNA species carrying the IVS 8 (-11delC) (-14T>A) mutation were detected by RT-PCR analysis of the RNA extracted from the patients' fibroblasts. To study the possible effects of the IVS 8 (-11delC) (-14T>A) sequence alteration on the splicing of the proximal exon 9, we have established an in vitro system generating a minigene carrying the genomic region of human glucocerebrosidase spanning from exon 8 to exon 10. Transfections into the human Hep3B cell line of the wild-type construct resulted in the expression of mRNA with the glucocerebrosidase exons correctly spliced. On the contrary, transfections of the construct carrying the IVS 8 (-11delC) (-14T>A) mutation resulted in the expression of mRNA with an 11-bp insertion located between the end of exon 8 and the beginning of exon 9. These results indicated that the 5243T>A substitution created a new 3' splice site 11 bp upstream of the wild-type one, leading to the incorporation into the mRNA of these extra 11 bases. Moreover, the new 3' splice site created by this 5243T>A transversion was preferred over the wild-type one in 100% of cases. The in vitro studies suggest that, in the patients, the 11-bp inclusion causes a shift in the reading frame with the generation of a stop codon after codon 388 which undergoes early degradation.

An Asn > Lys substitution in saposin B involving a conserved amino acidic residue and leading to the loss of the single N-glycosylation site in a patient with metachromatic leukodystrophy and normal arylsulphatase A activity

Sphingolipid activator proteins are small glycoproteins required for the degradation of sphingolipids by specific lysosomal hydrolases. Four of them, called saposins, are encoded by the prosaposin gene, the product of which is proteolytically cleaved into the four mature saposin proteins (saposins A, B, C, D). One of these, saposin B, is necessary in the hydrolysis of sulphatide by arylsulphatase A where it presents the solubilised substrate to the enzyme. As an alternative to arylsulphatase A deficiency, deficiency of saposin B causes metachromatic leukodystrophy. We identified a previously undescribed mutation (N215K) in the prosaposin gene of a patient with metachromatic leukodystrophy but with normal arylsulphatase A activity and elevated sulphatide in urine. The mutation involves a highly conserved amino acidic residue and abolishes the only N-glycosylation site of saposin B.

A deletion involving exons 2-4 in the iduronate-2-sulfatase gene of a patient with intermediate Hunter syndrome

A large deletion in the iduronate-2-sulfatase (IDS) gene has been found in a patient affected by an intermediate form of Hunter syndrome (mucopolysaccharidosis II). The deletion involves exons 2-4, the breakpoints lying respectively in intron 1, at position 376, and in intron 4, at position 5725. cDNA analysis revealed a direct exon 1-exon 5 junction due to the deletion resulting in a frameshift mutation.

A novel mutation of the beta-glucocerebrosidase gene associated with neurologic manifestations in three sibs

We report on a sibship in which three members were affected by Gaucher disease. Molecular analysis of the patients showed homozygosity for a novel mutation (C5390G) of the beta-glucocerebrosidase gene, resulting in the substitution of the arginine 353 with a glycine. Western blot analysis showed a reduced amount of beta-glucocerebrosidase-related polypeptides in fibroblasts. The phenotype resulting from this mutation is characterized by visceral and skeletal manifestations. In addition, the presence of seizures and electrophysiological abnormalities only in the 3 patients and in none of the other unaffected sibs suggests that the mutation is responsible for neurologic involvement.

Pulmonary manifestations of Gaucher disease: an increased risk for L444P homozygotes?

Pulmonary disease is a complication of Gaucher disease (GD), a lysosomal disorder due to the deficiency of glucocerebrosidase. Lung involvement was investigated through chest radiography, high-resolution computed tomography of the chest, pulmonary function tests (PFT), and oxygen saturation (SaO2) at 21% FI(O2) in 13 Italian GD patients, six homoallelic for the L444P mutation (Group A), seven with various genotypes (Group B). Echocardiography and transcutaneous oxygen tension measurement at room air and after breathing 100% oxygen were performed to exclude pulmonary hypertension and/or intrapulmonary shunts. A score index (SI) including lung involvement evaluated the severity of GD. In three Group A patients with respiratory symptoms and in an asymptomatic male interstitial involvement was demonstrated; one child died of aspiration pneumonia. Group B patients had no signs of lung damage; PFT were normal in all cases but one. SaO2 was normal in both groups. Pulmonary vascular disease was ruled out in three cases with respiratory symptoms. In Groups A and B the median SI were 22 and 13, respectively (p < 0.01). L444P homozygotes appear at major risk for developing pulmonary disease, even at earlier ages. A comprehensive evaluation of lung involvement is recommended primarily in these subjects.

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.

Mutations among Italian mucopolysaccharidosis type I patients

A group of 27 Italian patients was screened for alpha-L-iduronidase mucopolysaccharidosis type I mutations. Mutations were found in 18 patients, with 28 alleles identified. The two most common mutations in northern Europeans (W402X and Q70X) accounted for 11% and 13% of the alleles, respectively. The R89Q mutation, uncommon in Europeans, was found only in one patient, accounting for 1 of 54 alleles (1.9%). The other mutations, P533R, A327P and G51D, accounted for 11%, 5.6% and 9.3% of the total alleles, respectively. Interestingly, the high frequency of the P533R mutation seems to be confined to Sicily and is higher than the 3% reported in a British/Australian study.

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.

Mutations in fucosidosis gene: a review

Fucosidosis is an autosomal recessive disorder caused by a deficiency of alpha-L-fucosidase. Up to now 79 cases have been described and several others identified but not yet published. The higher incidence of the disease is in Italy, where nearly 20 patients have been identified. Fourteen disease-causing mutations have been detected and four of them, Q422X, G60D, E375X, P141fs are present in more than 70% of the forty patients studied. In Italian patients, only seven mutations have been described and P141fs and G60D mutations are present in more than 50% of the cases. The P141fs mutation is absent in other ethnic groups. It has been impossible to establish genotype-phenotype correlation so far and the clinical variability of the disease cannot be explained only by genetic heterogeneity.

A rare G6490-->A substitution at the last nucleotide of exon 10 of the glucocerebrosidase gene in two unrelated Italian Gaucher patients

Mutation screening of the glucocerebrosidase gene by SSCP analysis revealed an abnormal pattern of exon 10 in two unrelated Italian Gaucher patients. Direct sequencing of the mutated samples identified a G6490-->A transition. The same mutation has been described before in a Japanese patient with Gaucher disease type III. The clinical phenotype of our patients was type I in one whose second allele carried the N370S mutation and type II in the other one with a L444P mutation. In this latter the G6490-->A substitution cancels a normal Msp I site, while on the opposite chromosome the T6433-->C mutation (L444P) introduces a new Msp I site. Thus, digestion with Msp I of the amplified exon 10 is a useful method for identifying the two mutations simultaneously.

An AT-deletion causing a frameshift in the arylsulfatase A gene of a late infantile metachromatic leukodystrophy patient

A metachromatic leukodystrophy (MLD) patient affected with the late infantile form was found to be homozygous for an AT-deletion (2324delAT) in the arylsulfatase A gene. The mutation causes a frameshift at the beginning of exon 8 leading to an early termination codon. The parents and unaffected brother of the patient were heterozygous for the microdeletion. The mutation was not detected in another 31 MLD Italian patients. No aberrant transcript caused by the mutation was revealed by the reverse transcription-polymerase chain reaction method.