title: Intronic mutations outside of Alu-repeat-rich domains of the LDL receptor gene are a cause of familial hypercholesterolemia.
abstract: Familial hypercholesterolemia (FH), a frequent monogenic condition complicated by premature cardiovascular disease, is characterized by high allelic heterogeneity at the low-density lipoprotein receptor ( LDLR) locus. Despite more than a decade of genetic testing, knowledge about intronic disease-causing mutations has remained limited because of lack of available genomic sequences. Based on the finding from bioinformatic analysis that Alu repeats represent 85% of LDLR intronic sequences outside exon-intron junctions, we designed a strategy to improve the exploration of genomic regions in the vicinity of exons in 110 FH subjects from an admixed population. In the first group of 42 patients of negative mutation carriers, as previously established by former screening strategies (denaturing gradient gel electrophoresis, DNA sequencing with former primers overlapping splice-sites, Southern Blotting), about half ( n=22) were found to be carriers of at least one heterozygous mutation. Among a second group of 68 newly recruited patients, 27% of mutation carriers ( n=37) had a splicing regulatory mutation. Overall, out of the 54 mutations identified, 13 were intronic, and 18 were novel, out of which nearly half were intronic. Two novel intronic mutations (IVS8-10G-->A within the polypyrimidine tract and IVS7+10G-->A downstream of donor site) might create potential aberrant splice sites according to neural-network computed estimation, contrary to 31 common single nucleotide variations also identified at exon-intron junctions. This new strategy of detecting the most likely disease-causing LDLR mutations outside of Alu-rich genomic regions reveals that intronic mutations may have a greater impact than previously reported on the molecular basis of FH.
authors.affiliation: Department of Biochemistry and Molecular Biology, APHP Saint Antoine Hospital, Paris, France.
authors.forename: Sabine
authors.initials: S
authors.lastname: Amsellem
authors.forename: Dorothée
authors.initials: D
authors.lastname: Briffaut
authors.forename: Alain
authors.initials: A
authors.lastname: Carrié
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: Rabès
authors.forename: Jean Philippe
authors.initials: JP
authors.lastname: Girardet
authors.forename: Alexandre
authors.initials: A
authors.lastname: Fredenrich
authors.forename: Philippe
authors.initials: P
authors.lastname: Moulin
authors.forename: Michel
authors.initials: M
authors.lastname: Krempf
authors.forename: Yves
authors.initials: Y
authors.lastname: Reznik
authors.forename: Bernard
authors.initials: B
authors.lastname: Vialettes
authors.forename: Jean Luc
authors.initials: JL
authors.lastname: de Gennes
authors.forename: Eric
authors.initials: E
authors.lastname: Brukert
authors.forename: Pascale
authors.initials: P
authors.lastname: Benlian
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D005091:Exons; D006801:Humans; D006938:Hyperlipoproteinemia Type II / Q000235:genetics*; D007438:Introns; D009154:Mutation; D011973:Receptors, LDL / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: D017931:DNA Primers; D011973:Receptors, LDL