MOLECULAR DEFECT IN HUMAN ERYTHROPOIETIC PROTOPORPHYRIA WITH FATAL LIVER-FAILURE

We investigated the molecular basis of ferrochelatase in a Japanese pa tient with erythropoietic protoporphyria (EPP), complicated by fatal l iver failure, and defined a novel point mutation in the ferrochelatase gene. cDNAs were synthesized using Epstein-Barr-virus-transformed lym phoblastoid cells from the proband. cDNA clones encoding ferrochelatas e in the proband were isolated by amplification using the polymerase c hain reaction. There were two sizes of ferrochelatase cDNAs; one was n ormal in size, the other being smaller. Sequence analysis of the abnor mally sized cDNA clones revealed that they lacked exon 9 of the ferroc helatase gene. Genomic DNA analysis demonstrated that the proband had the abnormal allele and that it contained a G to A point mutation at t he first position of the donor site of intron 9. An identical mutation was detected in the affected family members of the proband by allele- specific oligonucleotide hybridization analysis. EPP is inherited in a n autosomal dominant manner in this family.