title: Gene dosage analysis identifies large deletions of the FECH gene in 10% of families with erythropoietic protoporphyria.
abstract: Erythropoietic protoporphyria (EPP) is an inherited cutaneous porphyria characterized by partial deficiency of ferrochelatase (FECH), accumulation of protoporphyrin IX in erythrocytes, skin, and liver, and acute photosensitivity. Genetic counseling in EPP requires identification of FECH mutations, but current sequencing-based procedures fail to detect mutations in about one in six families. We have used gene dosage analysis by quantitative PCR to identify large deletions of the FECH gene in 19 (58%) of 33 unrelated UK patients with EPP in whom mutations could not be detected by sequencing. Seven deletions were identified, six of which were previously unreported. Breakpoints were identified for six deletions (c.1-7887-IVS1+2425insTTCA; c.1-9629-IVS1+2437; IVS2-1987-IVS4+352del; c.768-IVS7+244del; IVS7+2784-IVS9+108del; IVS6+2350-TGA+95del). Five breakpoints were in intronic repeat sequences (AluSc, AluSq, AluSx, L1MC4). The remaining deletion (Del Ex3-4) is likely to be a large insertion-deletion. Combining quantitative PCR with routine sequencing increased the sensitivity of mutation detection in 189 unrelated UK patients with EPP from 83% (95% CI: 76-87%) to 93% (CI: 88-96%) (P=0.003). Our findings show that large deletions of the FECH gene are an important cause of EPP. Gene dosage analysis should be incorporated into routine procedures for mutation detection in EPP.
authors.affiliation: Department of Medical Biochemistry and Immunology, University Hospital of Wales and School of Medicine, Cardiff University, Cardiff, UK. whatley@cardiff.ac.uk
authors.forename: Sharon D
authors.initials: SD
authors.lastname: Whatley
authors.forename: Nicola G
authors.initials: NG
authors.lastname: Mason
authors.forename: S Alexander
authors.initials: SA
authors.lastname: Holme
authors.forename: Alex V
authors.initials: AV
authors.lastname: Anstey
authors.forename: George H
authors.initials: GH
authors.lastname: Elder
authors.forename: Michael N
authors.initials: MN
authors.lastname: Badminton
mesh_terms: D004252:DNA Mutational Analysis; D005091:Exons; D005192:Family Health; D005294:Ferrochelatase / Q000235:genetics* / Q000502:physiology*; D017353:Gene Deletion; D018628:Gene Dosage; D006239:Haplotypes; D006801:Humans; D018895:Microsatellite Repeats; D009154:Mutation; D016133:Polymerase Chain Reaction; D046351:Protoporphyria, Erythropoietic / Q000235:genetics*; D011524:Protoporphyrins / Q000378:metabolism; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA
chemical_list: D011524:Protoporphyrins; C028025:protoporphyrin IX; D005294:Ferrochelatase