title: Niemann-Pick type C disease: mutations of NPC1 gene and evidence of abnormal expression of some mutant alleles in fibroblasts.
abstract: We analyzed Niemann-Pick type C disease 1 (NPC1) gene in 12 patients with Niemann-Pick type C disease by sequencing both cDNA obtained from fibroblasts and genomic DNA. All the patients were compound heterozygotes. We found 15 mutations, eight of which previously unreported. The comparison of cDNA and genomic DNA revealed discrepancies in some subjects. In two unrelated patients carrying the same mutations (P474L and nt 2972del2) only one mutant allele (P474L), was expressed in fibroblasts. The mRNA corresponding to the other allele was not detected even in cells incubated with cycloheximide. The promoter variants (-1026T/G and -1186T/C or -238 C/G), found to be in linkage with 2972del2 allele do not explain the lack of expression of this allele, as they were also found in control subjects. In another patient, (N1156S/Q922X) the N1156S allele was expressed in fibroblasts while the expression of the other allele was hardly detectable. In a fourth patient cDNA analysis revealed a point mutation in exon 20 (P1007A) and a 56 nt deletion in exon 22 leading to a frameshift and a premature stop codon. The first mutation was confirmed in genomic DNA; the second turned out to be a T-->G transversion in exon 22, predicted to cause a missense mutation (V1141G). In fact, this transversion generates a donor splice site in exon 22, which causes an abnormal pre-mRNA splicing leading to a partial deletion of this exon. In some NPC patients, therefore, the comparison between cDNA and genomic DNA may reveal an unexpected expression of some mutant alleles of NPC1 gene.
authors.affiliation: Dipartimento di Scienze Biomediche, Università di Modena e Reggio Emilia, Modena, Italy.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Tarugi
authors.forename: Giorgia
authors.initials: G
authors.lastname: Ballarini
authors.forename: Bruno
authors.initials: B
authors.lastname: Bembi
authors.forename: Carla
authors.initials: C
authors.lastname: Battisti
authors.forename: Silvia
authors.initials: S
authors.lastname: Palmeri
authors.forename: Francesca
authors.initials: F
authors.lastname: Panzani
authors.forename: Enza
authors.initials: E
authors.lastname: Di Leo
authors.forename: Cristina
authors.initials: C
authors.lastname: Martini
authors.forename: Antonio
authors.initials: A
authors.lastname: Federico
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Calandra
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons / Q000235:genetics; D005260:Female; D005347:Fibroblasts; D005786:Gene Expression Regulation / Q000235:genetics*; D005820:Genetic Testing; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D000077296:Niemann-Pick C1 Protein; D009542:Niemann-Pick Diseases / Q000235:genetics*; D011110:Polymorphism, Genetic / Q000235:genetics; D022821:RNA Splice Sites / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D018076:DNA, Complementary; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; C106881:NPC1 protein, human; D000077296:Niemann-Pick C1 Protein; D022821:RNA Splice Sites