DGGE analysis of the coproporphyrinogen oxidase gene: two new mutations inDNA from Danish patients with hereditary coproporphyria

The knowledge of at least 21 different mutations and several polymorphisms in the coproporphyrinogen oxidase (CPO) gene demonstrates that the molecula r basis of hereditary coproporphyria is heterogeneous. We developed a DGGE- based assay for the analysis of exons 2 to 7, including 14-96 nucleotides o f the flanking intronic sequences of the CPO gene. To render it suitable fo r the clinical diagnostic laboratory, we designed the assay to allow use of identical PCR conditions and the same DGGE gel for analyses of all the reg ions. Using this assay, and subsequent sequencing of gene regions containin g interallelic variations, two novel mutations in the CPO gene were identif ied: a missense mutation (607G-->A), leading to the substitution of an alan ine with a threonine, and a nonsense mutation (1281G-->A), giving rise to a stop codon 28 codons upstream to the wild-type stop codon.