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Lualdi S.,Ssd Laboratory Diagnosi Pre Postnatale Malattie Metaboliche | Tappino B.,Ssd Laboratory Diagnosi Pre Postnatale Malattie Metaboliche | Di Duca M.,Laboratorio Of Fisiopatologia Delluremia | Dardis A.,Centro Of Coordinamento Regionale Malattie Rare | And 9 more authors.
Human Mutation | Year: 2010

Sequence analysis of the X-linked iduronate-2-sulfatase (IDS) gene in two Hunter syndrome patients revealed a lack of concordance between IDS genomic DNA and cDNA. These individuals were found to be hemizygous respectively for a nonsense mutation [c.22C>T;p.R8X] and a frameshift micro-insertion [c.10insT;p.P4Sfs] in their genomic DNA. However, both wild-type and mutant IDS sequences were evident upon cDNA analysis. Similar discrepant results were also obtained in a third unrelated patient carrying the same p.R8X mutation. Since both p.R8X mutations were inherited from carrier mothers, somatic mosaicism could be excluded. Although the presence of wild-type IDS mRNA-transcripts was confirmed in all three patients by restriction enzyme digestion, clone sequencing, pyrosequencing and single nucleotide primer extension (SNuPE), no wild-type IDS genomic sequence was detectable. The relative abundance of wild-type and mutation-bearing IDS-transcripts in different tissues was quantified by SNuPE. Although IDS transcript levels, as measured by real-time PCR, were reduced (51-71% normal) in these patients, some wild-type IDS protein was detectable by western blotting. Various possible explanations for these unprecedented findings (e.g. accidental contamination, artefactual in vitro nucleotide misincorporation, malsegregation of an extra maternal X-chromosome) were explored and experimentally excluded. PCR-based discriminant assay and segregation analysis of a linked IDS polymorphism (rs1141608) also served to exclude the presence of IDS cDNA derived from the maternal wild-type chromosome. Although it remains to be formally demonstrated by direct experimentation, the intriguing possibility arises that we have observed the in vivo correction of heritable gene lesions at the RNA level operating via a correction mechanism akin to RNA-editing. ©2010 Wiley-Liss, Inc. Source


Tappino B.,Ssd Laboratory Diagnosi Pre Postnatale Malattie Metaboliche | Biancheri R.,U.O. Neuropsichiatria Infantile | Mort M.,University of Cardiff | Regis S.,Ssd Laboratory Diagnosi Pre Postnatale Malattie Metaboliche | And 9 more authors.
Human Mutation | Year: 2010

The characterization of the underlying GALC gene lesions was performed in 30 unrelated patients affected by Krabbe disease, an autosomal recessive leukodystrophy caused by the deficiency of lysosomal enzyme galactocerebrosidase. The GALC mutational spectrum comprised 33 distinct mutant (including 15 previously unreported) alleles. With the exception of 4 novel missense mutations that replaced evolutionarily highly conserved residues (p.P318R, p.G323R, p.I384T, p.Y490N), most of the newly described lesions altered mRNA processing. These included 7 frameshift mutations (c.61delG, c.408delA, c.521delA, c.1171_1175delCATTCinsA, c.1405_1407delCTCinsT, c.302_308dupAAATAGG, c.1819_1826dupGTTACAGG), 3 nonsense mutations (p.R69X, p.K88X, p.R127X) one of which (p.K88X) mediated the skipping of exon 2, and a splicing mutation (c.1489+1G>A) which induced the partial skipping of exon 13. In addition, 6 previously unreported GALC polymorphisms were identified. The functional significance of the novel GALC missense mutations and polymorphisms was investigated using the MutPred analysis tool. This study, reporting one of the largest genotype-phenotype analyses of the GALC gene so far performed in a European Krabbe disease cohort, revealed that the Italian GALC mutational profile differs significantly from other populations of European origin. This is due in part to a GALC missense substitution (p.G553R) that occurs at high frequency on a common founder haplotype background in patients originating from the Naples region. © 2010 Wiley-Liss, Inc. Source


Grossi S.,Ssd Laboratory Diagnosi Pre Postnatale Malattie Metaboliche | Regis S.,Ssd Laboratory Diagnosi Pre Postnatale Malattie Metaboliche | Biancheri R.,U.O. Neuropsichiatria Infantile | Mort M.,University of Cardiff | And 15 more authors.
Orphanet Journal of Rare Diseases | Year: 2011

Background: The breadth of the clinical spectrum underlying Pelizaeus-Merzbacher disease and spastic paraplegia type 2 is due to the extensive allelic heterogeneity in the X-linked PLP1 gene encoding myelin proteolipid protein (PLP). PLP1 mutations range from gene duplications of variable size found in 60-70% of patients to intragenic lesions present in 15-20% of patients. Methods. Forty-eight male patients from 38 unrelated families with a PLP1-related disorder were studied. All DNA samples were screened for PLP1 gene duplications using real-time PCR. PLP1 gene sequencing analysis was performed on patients negative for the duplication. The mutational status of all 14 potential carrier mothers of the familial PLP1 gene mutation was determined as well as 15/24 potential carrier mothers of the PLP1 duplication. Results and Conclusions. PLP1 gene duplications were identified in 24 of the unrelated patients whereas a variety of intragenic PLP1 mutations were found in the remaining 14 patients. Of the 14 different intragenic lesions, 11 were novel; these included one nonsense and 7 missense mutations, a 657-bp deletion, a microdeletion and a microduplication. The functional significance of the novel PLP1 missense mutations, all occurring at evolutionarily conserved residues, was analysed by the MutPred tool whereas their potential effect on splicing was ascertained using the Skippy algorithm and a neural network. Although MutPred predicted that all 7 novel missense mutations would be likely to be deleterious, in silico analysis indicated that four of them (p.Leu146Val, p.Leu159Pro, p.Thr230Ile, p.Ala247Asp) might cause exon skipping by altering exonic splicing elements. These predictions were then investigated in vitro for both p.Leu146Val and p.Thr230Ile by means of RNA or minigene studies and were subsequently confirmed in the case of p.Leu146Val. Peripheral neuropathy was noted in four patients harbouring intragenic mutations that altered RNA processing, but was absent from all PLP1-duplication patients. Unprecedentedly, family studies revealed the de novo occurrence of the PLP1 duplication at a frequency of 20%. © 2011 Grossi et al; licensee BioMed Central Ltd. Source

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