title: Intronic splicing mutations in PTCH1 cause Gorlin syndrome.
abstract: Gorlin syndrome is an autosomal dominant disorder characterized by multiple early-onset basal cell carcinoma, odontogenic keratocysts and skeletal abnormalities. It is caused by heterozygous mutations in the tumour suppressor PTCH1. Routine clinical genetic testing, by Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA) to confirm a clinical diagnosis of Gorlin syndrome, identifies a mutation in 60-90 % of cases. We undertook RNA analysis on lymphocytes from ten individuals diagnosed with Gorlin syndrome, but without known PTCH1 mutations by exonic sequencing or MLPA. Two altered PTCH1 transcripts were identified. Genomic DNA sequence analysis identified an intron 7 mutation c.1068-10T>A, which created a strong cryptic splice acceptor site, leading to an intronic insertion of eight bases; this is predicted to create a frameshift p.(His358Alafs*12). Secondly, a deep intronic mutation c.2561-2057A>G caused an inframe insertion of 78 intronic bases in the cDNA transcript, leading to a premature stop codon p.(Gly854fs*3). The mutations are predicted to cause loss of function of PTCH1, consistent with its tumour suppressor function. The findings indicate the importance of RNA analysis to detect intronic mutations in PTCH1 not identified by routine screening techniques.
authors.affiliation: Manchester Centre for Genomic Medicine, University of Manchester, Manchester, M13 9WL, UK.
authors.forename: Zaynab
authors.initials: Z
authors.lastname: Bholah
authors.forename: Miriam J
authors.initials: MJ
authors.lastname: Smith
authors.forename: Helen J
authors.initials: HJ
authors.lastname: Byers
authors.forename: Emma K
authors.initials: EK
authors.lastname: Miles
authors.forename: D Gareth
authors.initials: DG
authors.lastname: Evans
authors.forename: William G
authors.initials: WG
authors.lastname: Newman
mesh_terms: D001478:Basal Cell Nevus Syndrome / Q000235:genetics*; D001483:Base Sequence; D004252:DNA Mutational Analysis; D005260:Female; D006801:Humans; D007438:Introns; D008297:Male; D060885:Multiplex Polymerase Chain Reaction; D009154:Mutation; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; D022821:RNA Splice Sites / Q000235:genetics; D012326:RNA Splicing / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics*
chemical_list: C000606236:PTCH1 protein, human; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; D022821:RNA Splice Sites; D011956:Receptors, Cell Surface