Molecular analysis of the UROD gene in 17 Argentinean patients with familial porphyria cutanea tarda: characterization of four novel mutations.

Porphyria cutanea tarda (PCT) is caused by decreased activity of uroporphyrinogen decarboxylase (UROD) in the liver. The disease usually occurs in adulthood and is characterized by cutaneous photosensitivity, hyperpigmentation, skin fragility and hypertrichosis, due to the accumulation of porphyrins produced by oxidation of uroporphyrinogen and other highly carboxylated porphyrinogens overproduced as a result of the enzyme deficiency. PCT is generally sporadic, but about 20-30% of patients have familial-PCT (F-PCT) which is associated with heterozygosity of mutations in the UROD gene. In the present study we have found the molecular defect in seventeen unrelated Argentinean patients with F-PCT, identifying a total of eleven UROD gene mutations: four novel and seven previously described. The novel mutations were: a guanine insertion at the 5' splice junction of intron 2, a three nucleotide deletion causing the lost of valine 90, a deletion of 22 bp in exon 6 and a deletion of part of the polyadenylation signal. Prokaryotic expression studies showed that the novel amino acid deletion resulted in an inactive protein. Mutations c.10insA and p.M165R, previously found in Argentinean patients, were recurrent in this study; they are the most frequent in Argentina accounting for 40% of the mutant alleles characterized to date.

The very first description of a patient with hepatoerythropoietic porphyria in Argentina. Biochemical and molecular studies.

Hepatoerythropoietic Porphyria (HEP) is the rare homozygous form of Porphyria Cutanea Tarda (PCT). It is characterized clinically by the early onset of severe skin manifestations which can be confused with Congenital Erythropoietic Porphyria (CEP) or with PCT when the symptoms are mild. We describe the case of a 14 year-old child with skin manifestations similar to those observed in PCT. The biochemical assays ruled out a CEP as well as they suggested the development of a HEP. Although his symptoms were not severe enough to be HEP, the enzymatic activity was dramatically reduced to a 5% of normal values and the molecular analysis revealed the presence of two already known different mutations on the patient's URO-D gene, c.703 C>T and IVS9-1. Each parent carry one of the mutations, but they were absent in the brother. This is the first Argentinean HEP case ever described which appeared in a compound heterozygous form and less residual URO-D activity but associated to a mild phenotype.

[Mutations of hemochromatosis gene in volunteer blood donors and Chilean porphyria cutanea tarda patients]. / Mutaciones del gen de la hemocromatosis en donantes de sangre voluntarios y en pacientes con porfiria cutánea tarda en Chile.

In patients with porphyria cutanea tarda (PCT), hepatic iron accumulation associated to hereditary hemochromatosis (HH) could play a role in the etiology and in the clinical expression of the disease. The H63D and C282Y mutations of the HFE gene frequency were studied in a PCT group of patients and compared with the frequency observed in a group of volunteer blood donors. PCT patients were cataloged as hereditary or acquired PCT carriers, whether or not they presented uroporphyrinogen decarboxilase gene mutations. Fifty percent of PCT patients were carriers of the disease's genetic type. Such percentage is significantly higher than what other authors have previously informed. H63D and C282Y mutations were present in 23% and 2.4% of the volunteer blood donors, respectively. Similar frequencies were informed by others authors in Chilean white ethnic populations, and also in Spaniard and Argentinean populations, but significantly higher than that observed in Chile's Araucanean aboriginal population. Probably the frequency of H63D and C283Y mutations are related to the Spaniard ascendancy dominance of Chile's white ethnic population. The frequency of HFE gene mutations in PCT patients was not different than what was observed in volunteer blood donors. Similarly, there was no statistical difference in the frequency of these mutations among patients with acquired or genetic PCT disease. With the obtained results, it is not possible postulate an association between PCT and the hereditary hemochromatosis of HFE gene mutations carrier conditions.

Mutaciones del gen de la hemocromatosis en donantes de sangre voluntarios y en pacientes con porfiria cutanea tarda en chile / Mutations of hemochromatosis gene in volunteer blood donors and Chilean porphyria cutanea tarda patients

La acumulación de hierro hepático asociada a mutaciones en el gen HFE de la hemocromatosis hereditaria (HH) en los pacientes con porfiria cutánea tarda (PCT) podría tener un papel en la etiología y en la expresión clínica de esta enfermedad. Se estudió la frecuencia de las mutaciones H63D y C282Y en un grupo de pacientes con PCT y se la comparó con la observada en un grupo de donantes voluntarios desangre. Los pacientes con PCT fueron catalogados como portadores de la forma hereditaria o adquirida de laenfermedad, según presentaran o no mutaciones en el gen uroporfirinógeno decarboxilasa (UROD). El 50% delos pacientes con PCT eran portadores de la forma genética de la enfermedad, porcentaje significativamentemayor que lo informado en otras series. El 23% de los donantes voluntarios de sangre eran portadores de lamutación H63D y 2.4% lo era de la mutación C282Y. Frecuencias similares a lo encontrado por otros autoresen población chilena de etnia blanca, en población argentina y española, pero significativamente más alta quelo encontrado en estudios en población aborigen araucana. Esto tiene, probablemente, relación con el predominio de ascendencia española en la población blanca chilena. La frecuencia de mutación en el gen HFE en pacientes con PCT no fue significativamente diferente que la observada en donantes voluntarios de sangre. Tampoco hubo diferencias significativas en la frecuencia de estas mutaciones entre los casos con PCT adquirida respecto de aquellos en que ésta era de origen genético. Los resultados obtenidos no permiten afirmar que exista asociación entre la PCT y la condición de portador de mutaciones del gen HFE de la hemocromatosis hereditaria

In patients with porphyria cutanea tarda (PCT), hepatic iron accumulation associated to hereditary hemochromatosis (HH) could play a role in the etiology and in the clinical expression of the disease. The H63D and C282Y mutations of the HFE gene frequency were studied in a PCT group of patients and compared with the frequency observed in a group of volunteer blood donors. PCT patients were cataloged as hereditary or acquired PCT carriers, whether or not they presented uroporphyrinogen decarboxilase gene mutations. Fifty percent of PCT patients were carriers of the disease’s genetic type. Such percentage is significantlyhigher than what other authors have previously informed. H63D and C282Y mutations were present in23% and 2.4% of the volunteer blood donors, respectively. Similar frequencies were informed by others authors in Chilean white ethnic populations, and also in Spaniard and Argentinean populations, but significantly higherthan that observed in Chile’s Araucanean aboriginal population. Probably the frequency of H63D and C283Y mutations are related to the Spaniard ascendancy dominance of Chile’s white ethnic population. The frequency of HFE gene mutations in PCT patients was not different than what was observed in volunteer blood donors.Similarly, there was no statistical difference in the frequency of these mutations among patients with acquired or genetic PCT disease. With the obtained results, it is not possible postulate an association between PCT and the hereditary hemochromatosis of HFE gene mutations carrier conditions

Mutaciones del gen de la hemocromatosis en donantes de sangre voluntarios y en pacientes con porfiria cutanea tarda en chile / Mutations of hemochromatosis gene in volunteer blood donors and Chilean porphyria cutanea tarda patients

La acumulación de hierro hepático asociada a mutaciones en el gen HFE de la hemocromatosis hereditaria (HH) en los pacientes con porfiria cutánea tarda (PCT) podría tener un papel en la etiología y en la expresión clínica de esta enfermedad. Se estudió la frecuencia de las mutaciones H63D y C282Y en un grupo de pacientes con PCT y se la comparó con la observada en un grupo de donantes voluntarios desangre. Los pacientes con PCT fueron catalogados como portadores de la forma hereditaria o adquirida de laenfermedad, según presentaran o no mutaciones en el gen uroporfirinógeno decarboxilasa (UROD). El 50% delos pacientes con PCT eran portadores de la forma genética de la enfermedad, porcentaje significativamentemayor que lo informado en otras series. El 23% de los donantes voluntarios de sangre eran portadores de lamutación H63D y 2.4% lo era de la mutación C282Y. Frecuencias similares a lo encontrado por otros autoresen población chilena de etnia blanca, en población argentina y española, pero significativamente más alta quelo encontrado en estudios en población aborigen araucana. Esto tiene, probablemente, relación con el predominio de ascendencia española en la población blanca chilena. La frecuencia de mutación en el gen HFE en pacientes con PCT no fue significativamente diferente que la observada en donantes voluntarios de sangre. Tampoco hubo diferencias significativas en la frecuencia de estas mutaciones entre los casos con PCT adquirida respecto de aquellos en que ésta era de origen genético. Los resultados obtenidos no permiten afirmar que exista asociación entre la PCT y la condición de portador de mutaciones del gen HFE de la hemocromatosis hereditaria (AU)

In patients with porphyria cutanea tarda (PCT), hepatic iron accumulation associated to hereditary hemochromatosis (HH) could play a role in the etiology and in the clinical expression of the disease. The H63D and C282Y mutations of the HFE gene frequency were studied in a PCT group of patients and compared with the frequency observed in a group of volunteer blood donors. PCT patients were cataloged as hereditary or acquired PCT carriers, whether or not they presented uroporphyrinogen decarboxilase gene mutations. Fifty percent of PCT patients were carriers of the diseaseãs genetic type. Such percentage is significantlyhigher than what other authors have previously informed. H63D and C282Y mutations were present in23% and 2.4% of the volunteer blood donors, respectively. Similar frequencies were informed by others authors in Chilean white ethnic populations, and also in Spaniard and Argentinean populations, but significantly higherthan that observed in Chileãs Araucanean aboriginal population. Probably the frequency of H63D and C283Y mutations are related to the Spaniard ascendancy dominance of Chileãs white ethnic population. The frequency of HFE gene mutations in PCT patients was not different than what was observed in volunteer blood donors.Similarly, there was no statistical difference in the frequency of these mutations among patients with acquired or genetic PCT disease. With the obtained results, it is not possible postulate an association between PCT and the hereditary hemochromatosis of HFE gene mutations carrier conditions (AU)

Mutaciones del gen de la hemocromatosis en donantes de sangre voluntarios y en pacientes con porfiria cutanea tarda en chile / Mutations of hemochromatosis gene in volunteer blood donors and Chilean porphyria cutanea tarda patients

La acumulación de hierro hepático asociada a mutaciones en el gen HFE de la hemocromatosis hereditaria (HH) en los pacientes con porfiria cutánea tarda (PCT) podría tener un papel en la etiología y en la expresión clínica de esta enfermedad. Se estudió la frecuencia de las mutaciones H63D y C282Y en un grupo de pacientes con PCT y se la comparó con la observada en un grupo de donantes voluntarios desangre. Los pacientes con PCT fueron catalogados como portadores de la forma hereditaria o adquirida de laenfermedad, según presentaran o no mutaciones en el gen uroporfirinógeno decarboxilasa (UROD). El 50% delos pacientes con PCT eran portadores de la forma genética de la enfermedad, porcentaje significativamentemayor que lo informado en otras series. El 23% de los donantes voluntarios de sangre eran portadores de lamutación H63D y 2.4% lo era de la mutación C282Y. Frecuencias similares a lo encontrado por otros autoresen población chilena de etnia blanca, en población argentina y española, pero significativamente más alta quelo encontrado en estudios en población aborigen araucana. Esto tiene, probablemente, relación con el predominio de ascendencia española en la población blanca chilena. La frecuencia de mutación en el gen HFE en pacientes con PCT no fue significativamente diferente que la observada en donantes voluntarios de sangre. Tampoco hubo diferencias significativas en la frecuencia de estas mutaciones entre los casos con PCT adquirida respecto de aquellos en que ésta era de origen genético. Los resultados obtenidos no permiten afirmar que exista asociación entre la PCT y la condición de portador de mutaciones del gen HFE de la hemocromatosis hereditaria (AU)

In patients with porphyria cutanea tarda (PCT), hepatic iron accumulation associated to hereditary hemochromatosis (HH) could play a role in the etiology and in the clinical expression of the disease. The H63D and C282Y mutations of the HFE gene frequency were studied in a PCT group of patients and compared with the frequency observed in a group of volunteer blood donors. PCT patients were cataloged as hereditary or acquired PCT carriers, whether or not they presented uroporphyrinogen decarboxilase gene mutations. Fifty percent of PCT patients were carriers of the diseaseãs genetic type. Such percentage is significantlyhigher than what other authors have previously informed. H63D and C282Y mutations were present in23% and 2.4% of the volunteer blood donors, respectively. Similar frequencies were informed by others authors in Chilean white ethnic populations, and also in Spaniard and Argentinean populations, but significantly higherthan that observed in Chileãs Araucanean aboriginal population. Probably the frequency of H63D and C283Y mutations are related to the Spaniard ascendancy dominance of Chileãs white ethnic population. The frequency of HFE gene mutations in PCT patients was not different than what was observed in volunteer blood donors.Similarly, there was no statistical difference in the frequency of these mutations among patients with acquired or genetic PCT disease. With the obtained results, it is not possible postulate an association between PCT and the hereditary hemochromatosis of HFE gene mutations carrier conditions (AU)

The molecular basis of porphyria cutanea tarda in Chile: identification and functional characterization of mutations in the uroporphyrinogen decarboxylase gene.

The porphyrias are heterogeneous disorders arising from predominantly inherited catalytic deficiencies of specific enzymes in heme biosynthesis. Porphyria cutanea tarda (PCT) results from a decreased activity of uroporphyrinogen decarboxylase, the fifth enzyme in heme biosynthesis. The disorder represents the only porphyria that is not exclusively inherited monogenetically. In PCT, at least two different types can be distinguished: acquired/sporadic (type I) PCT, in which the enzymatic deficiency is limited to the liver and inherited/familial (type II) PCT, which is inherited as an autosomal dominant trait with a decrease of enzymatic activity in all tissues. In an effort to characterize the molecular basis of PCT in Chile, we identified eight mutations in 18 previously unclassified PCT families by polymerase chain reaction, heteroduplex analysis, and automated sequencing. To study the role of these mutations in disease causality, in vitro expression of all novel missense mutations was studied. Our results indicate that the frequency of familial PCT in Chile is approximately 50%, thus, to our knowledge, representing the highest incidence of familial PCT reported to date. The data further emphasize the molecular heterogeneity in type II PCT and demonstrate the advantages of molecular genetic techniques as a diagnostic tool and in the detection of clinically asymptomatic mutation carriers.

Mutations in familial porphyria cutanea tarda: two novel and two previously described for hepatoerythropoietic porphyria.

Uroporphyrinogen decarboxylase (URO-D) deficiency is responsible for two forms of genetic cutaneous porphyria: familial porphyria cutanea tarda (f-PCT) and hepatoerythropoietic porphyria (HEP). The f-PCT transmitted as an autosomal dominant trait, is characterized by photosensitive cutaneous lesions frequently associated to hepatic dysfunction and is precipitated by various ecogenic factors. The HEP, transmitted as a recessive trait, is more severe than f-PCT and would be considered as the homozygous form of f-PCT. For the mutational analysis of f-PCT patients, the entire URO-D gene was amplified and each exon, intron-exon boundaries and the promoter region were cycle sequenced. Five mutations were found in 6 unrelated families studied, of these, two were new: a nonsense mutation in exon 6 (W159X) and a splice defect in intron 9 (IVS9(-1)G-->C). The other two missense mutations, P62L and A80G, had been previously reported in the homozygous state in HEP families. The g10insA, reported in our laboratory, was again identified in other two unrelated families. In addition 3 novel URO-D polymorphisms in non-coding regions were found. The reverse transcription-PCR and sequencing of the splice mutation carrier's RNA did not reveal the presence of an abnormal mRNA, suggesting that no stable transcript from the mutated allele is synthesized. These results increase to 39 the number of mutations identified in the URO-D gene; 4 of them causing both HEP and f-PCT.

Porphyrin biosynthesis intermediates are not regulating delta-aminolevulinic acid transport in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, as in all eukaryotic organisms, delta-aminolevulinic acid (ALA) is a precursor of porphyrin biosynthesis, a very finely regulated pathway. ALA enters yeast cells through the gamma-aminobutyric acid (GABA) permease Uga4. The incorporation of a metabolite into the cells may be a limiting step for its intracellular metabolization. To determine the relationship between ALA transport and ALA metabolization, ALA incorporation was measured in yeast mutant strains deficient in the delta-aminolevulinic acid-synthase, uroporphyrinogen III decarboxylase, and ferrochelatase, three enzymes involved in porphyrin biosynthesis. Results presented here showed that neither intracellular ALA nor uroporphyrin or protoporphyrin regulates ALA incorporation, indicating that ALA uptake and its subsequent metabolization are not related to each other. Thus a key metabolite as it is, ALA does not have a transport system regulated according to its role.

Familial porphyria cutanea tarda: characterization of seven novel uroporphyrinogen decarboxylase mutations and frequency of common hemochromatosis alleles.

Familial porphyria cutanea tarda (f-PCT) results from the half-normal activity of uroporphyrinogen decarboxylase (URO-D). Heterozygotes for this autosomal dominant trait are predisposed to photosensitive cutaneous lesions by various ecogenic factors, including iron overload and alcohol abuse. The 3.6-kb URO-D gene was completely sequenced, and a long-range PCR method was developed to amplify the entire gene for mutation analysis. Four missense mutations (M165R, L195F, N304K, and R332H), a microinsertion (g10insA), a deletion (g645Delta1053), and a novel exonic splicing defect (E314E) were identified. Expression of the L195F, N304K, and R332H polypeptides revealed significant residual activity, whereas reverse transcription-PCR and sequencing demonstrated that the E314E lesion caused abnormal splicing and exon 9 skipping. Haplotyping indicated that three of the four families with the g10insA mutation were unrelated, indicating that these microinsertions resulted from independent mutational events. Screening of nine f-PCT probands revealed that 44% were heterozygous or homozygous for the common hemochromatosis mutations, which suggests that iron overload may predispose to clinical expression. However, there was no clear correlation between f-PCT disease severity and the URO-D and/or hemochromatosis genotypes. These studies doubled the number of known f-PCT mutations, demonstrated that marked genetic heterogeneity underlies f-PCT, and permitted presymptomatic molecular diagnosis and counseling in these families to enable family members to avoid disease-precipitating factors.