Defects in the enzymes involved in the haem biosynthetic pathway can l
ead to a group of human diseases known as the porphyrias. yquem (yqe(t
p61)) is a zebrafish mutant with a photosensitive porphyria syndrome.
Here we show that the porphyric phenotype is due to an inherited homoz
ygous mutation in the gene encoding uroporphyrinogen decarboxylase (UR
OD); a homozygous deficiency of this enzyme causes hepatoerythropoieti
c porphyria (HEP) in humans. The zebrafish mutant represents the first
genetically 'accurate' animal model of HEP, and should be useful for
studying the pathogenesis of UROD deficiency and evaluating gene thera
py vectors.. We rescued the mutant phenotype by transient and germline
expression of the wild-type allele.