Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0349506 (photosensitivity)
 4,145 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Erythropoietic protoporphyria (EPP) is an inherited defect of the ferrochelatase (FECH) gene characterized by the accumulation of toxic protoporphyrin in the liver and bone marrow resulting in severe skin photosensitivity. We previously described successful gene therapy of an animal model of the disease with erythroid-specific lentiviral vectors in the absence of preselection of corrected cells. However, the high-level of gene transfer obtained in mice is not translatable to large animal models and humans if there is no selective advantage for genetically modified hematopoietic stem cells (HSCs) in vivo. We used bicistronic SIN-lentiviral vectors coexpressing EGFP or FECH and the G156A-mutated O6-methylguanine-DNA-methyltransferase (MGMT) gene, which allowed efficient in vivo selection of transduced HSCs after O6-benzylguanine and BCNU treatment. We demonstrate for the first time that the correction and in vivo expansion of deficient transduced HSC population can be obtained by this dual gene therapy, resulting in a progressive increase of normal RBCs in EPP mice and a complete correction of skin photosensitivity. Finally, we developed a novel bipromoter SIN-lentiviral vector with a constitutive expression of MGMT gene to allow the selection of HSCs and with an erythroid-specific expression of the FECH therapeutic gene.
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PMID:Hematopoietic stem cell gene therapy of murine protoporphyria by methylguanine-DNA-methyltransferase-mediated in vivo drug selection. 1528 38

Erythropoietic protoporphyria (EPP) is caused by a defect in ferrochelatase, leading to the accumulation of protoporphyrin predominantly in erythrocytes and hepatocytes, and resulting in skin photosensitivity upon leaching of blood protoporphyrin into the skin. Some patients also develop severe liver damage. Because the respective contributions of hepatic and erythrocytic protoporphyrin to the pathophysiology of EPP remain unclear, we investigated this question using the murine model of EPP. Transplantation of bone marrow from EPP mice to normal recipients resulted in elevated erythrocyte and plasma protoporphyrin levels. However, quantification of serum liver enzymes and bilirubin together with histopathologic examination of liver sections of mice up to 16 months post-transplantation showed no evidence of liver damage. Moreover, despite massive elevation of serum protoporphyrin, transplanted mice showed minimal evidence of skin photosensitivity. Photosensitivity could also be prevented locally by implanting skin grafts from normal mice onto the backs of EPP recipients. These data validate the hypothesis that the main source of toxic protoporphyrin originates from the erythrocytes. However, we unexpectedly observed that normal ferrochelatase activity in hepatic and dermal cells of wild-type mice is sufficient to prevent liver disease and significant skin photosensitivity. These findings may provide new strategies for the treatment of EPP.
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PMID:Prevention of murine erythropoietic protoporphyria-associated skin photosensitivity and liver disease by dermal and hepatic ferrochelatase. 1565 46

Erythropoietic protoporphyria is an inherited disorder of heme biosynthesis caused by partial ferrochelatase deficiency, resulting in protoporphyrin (PP) overproduction by erythrocytes. In humans, it is responsible for painful skin photosensitivity and, occasionally, liver failure due to accumulation of PP in the liver. The ferrochelatase deficiency mouse mutation is the best animal model available for human erythropoietic protoporphyria. The original description, based on mice with a BALB/cByJCrl genetic background, reported a disease resembling the severe form of the human disease, with anemia, jaundice, and liver failure. Using congenic strains, we investigated the effect of genetic background on the severity of the phenotype. Compared with BALB/cByJCrl, C57BL/6JCrl mice developed moderate but increasing anemia and intense liver accumulation of PP with severe hepatocyte damage and loss. Bile excretory function was not affected, and bilirubin remained low. Despite the highest PP concentration in erythrocytes, anemia was mild and there were few PP deposits in the liver in SJL/JOrlCrl homozygotes. Discriminant analysis using six hematologic and biochemical parameters showed that homozygotes of the three genetic backgrounds could be clustered in three well-separated groups. These three congenic strains provide strong evidence for independent genetic control of bone marrow contribution of PP overproduction to development of liver disease and biliary PP excretion. They provide a tool to investigate the physiological mechanisms involved in these phenotypic differences and to identify modifying genes.
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PMID:A mouse model provides evidence that genetic background modulates anemia and liver injury in erythropoietic protoporphyria. 1567 51

Late-onset erythropoietic protoporphyria (EPP) is a rare complication of myelodysplastic syndrome (MDS) but has not been described in association with a myeloproliferative disorder (MPD). EPP is normally an inherited disorder characterized by photosensitivity that starts in early childhood and results from overproduction of protoporphyrin secondary to ferrochelatase (FECH) deficiency. Severe liver disease occurs in 1% to 2% of patients. Here we report that severe photosensitivity and cholestatic liver disease in a patient with a myeloproliferative disorder was caused by excess protoporphyrin production from a clone of hematopoietic cells in which one FECH allele had been deleted. Our observations suggest that the usual explanation for the association of late-onset EPP with MPD and MDS is acquired somatic mutation of one FECH allele in bone marrow and show for the first time that the consequent overproduction of protoporphyrin may be severe enough to cause acute liver damage.
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PMID:Photosensitivity and acute liver injury in myeloproliferative disorder secondary to late-onset protoporphyria caused by deletion of a ferrochelatase gene in hematopoietic cells. 1615 Sep 49

Erythropoietic protoporphyria (EPP) is an inherited disorder of heme biosynthesis that results from a partial deficiency of ferrochelatase (FECH). Recently, we have shown that the inheritance of the common hypomorphic IVS3-48C allele trans to a deleterious mutation reduces FECH activity to below a critical threshold and accounts for the photosensitivity seen in patients. Rare cases of autosomal recessive inheritance have been reported. We studied a cohort of 173 white French EPP families and a group of 360 unrelated healthy subjects from four ethnic groups. The prevalences of the recessive and dominant autosomal forms of EPP are 4% (95% confidence interval 1-8) and 95% (95% confidence interval 91-99), respectively. In 97.9% of dominant cases, an IVS3-48C allele is co-inherited with the deleterious mutation. The frequency of the IVS3-48C allele differs widely in the Japanese (43%), southeast Asian (31%), white French (11%), North African (2.7%), and black West African (<1%) populations. These differences can be related to the prevalence of EPP in these populations and could account for the absence of EPP in black subjects. The phylogenic origin of the IVS3-48C haplotypes strongly suggests that the IVS3-48C allele arose from a single recent mutational event. Estimation of the age of the IVS3-48C allele from haplotype data in white and Asian populations yields an estimated age three to four times younger in the Japanese than in the white population, and this difference may be attributable either to differing demographic histories or to positive selection for the IVS3-48C allele in the Asian population. Finally, by calculating the KA/KS ratio in humans and chimpanzees, we show that the FECH protein sequence is subject to strong negative pressure. Overall, EPP looks like a Mendelian disorder, in which the prevalence of overt disease depends mainly on the frequency of a single common single-nucleotide polymorphism resulting from a unique mutational event that occurred 60,000 years ago.
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PMID:Contribution of a common single-nucleotide polymorphism to the genetic predisposition for erythropoietic protoporphyria. 1638 45

Over the course of one year, slight jaundice and ascites suggestive of chronic liver disease occurred in 17 German shepherd dogs from one breeding colony. Blood analyses, performed twice with a six-month interval, revealed elevated serum activities of liver enzymes in 13 dogs. In addition, four young adult German shepherd dogs that showed severe ascites, slight jaundice and increased serum liver enzyme activities were referred for further evaluation. Because of their poor prognosis these four dogs were euthanased. There were no signs of photosensitivity. Postmortem examinations revealed macronodular darkened livers, which were characterised histopathologically by cirrhosis associated with aggregates of brown pigments showing a striking orange birefringence in polarised light. Ultrastructurally, the crystalline pigments were typical of protoporphyrins. High-performance liquid chromatographic analysis of liver samples revealed very high levels of protoporphyrins (mean 9550 nmol/g wet liver, reference value 0.41 nmol/g wet liver) and low activities of ferrochelatase (mean 0.274 mmol/mg protein/hour, reference value 0.684 nmol/mg protein/hour). Twenty-six months after the onset of the hepatopathies, the clinical condition of the 13 surviving dogs had improved and their serum liver enzyme activities were normal. The clinical histories and pedigree analyses were not in concordance with an inherited form of protoporphyria. There was no known history of exposure to toxic substances or drugs. The findings are in accordance with a transient erythropoietic protoporphyria associated with hepatic complications, presumably caused by exposure to a porphyrinogenic, ferrochelatase-inhibitory substance of unknown origin.
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PMID:Transient erythropoietic protoporphyria associated with chronic hepatitis and cirrhosis in a cohort of German shepherd dogs. 1644 37

Erythropoietic protoporphyria (EPP) results from an inherited partial deficiency of ferrochelatase, the terminal enzyme of haem biosynthesis. Excess protoporphyrin IX accumulates in erythrocytes, plasma, liver, and skin, which mediates a distinctive form of cutaneous photosensitivity that manifests during childhood. Ferrochelatase is synthesised on cytosolic ribosomes as a preprotein with a cleavable presequence at its amino-terminus. This leader sequence is thought to target ferrochelatase to mitochondria where it is cleaved to produce the active mature protein. In this study, we show that the 62 amino acid leader sequence is sufficient for targeting of a leader sequence-YFP fusion protein to mitochondria. A truncated fusion protein lacking the first 62 amino acids did not target to mitochondria, and formed punctate aggregates in the cytoplasm of cells. This suggests that all the information required for mitochondrial localisation resides within the first 62 amino acid presequence. A missense mutation, P62R, predicted to be located within the ferrochelatase presequence has been identified in a patient with EPP. We hypothesised that this mutation may exert its effect through defective targeting to mitochondria. Our data showed that this mutated full-length ferrochelatase successfully targeted to mitochondria. Interestingly, there was inhibited cleavage of YFP from wild-type and mutant leader sequence fusion proteins. Generation of leader sequence-YFP fusion proteins containing an additional 11 amino acids from the mature protein allowed proteolytic processing to occur. These data suggest that the first 62 amino acids allow targeting to mitochondria but do not contain sufficient information for efficient processing of the protein.
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PMID:Erythropoietic protoporphyria: a functional analysis of the leader sequence of human ferrochelatase. 1684 98

We report a patient aged 73 years, who developed erythropoietic protoporphyria with typical photosensitivity, at the same time as she was diagnosed as having myelodysplastic syndrome. The myelodysplastic clone in her bone marrow completely lacked one of the two copies of chromosome 18. As chromosome 18 is the locus of the ferrochelatase gene, we postulate that this chromosomal deletion led to reduced synthesis of the enzyme in the bone marrow clone, so causing the porphyria. The nature of the remaining ferrochelatase allele was examined by polymorphism analysis and we discuss the insights that this patient's genotype may reveal about the pathogenesis of porphyria in myelodysplasia.
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PMID:Acquired erythropoietic protoporphyria as a result of myelodysplasia causing loss of chromosome 18. 1688 91

Patients with deficiency in ferrochelatase (FECH), the last enzyme of the heme biosynthetic pathway, experience a painful type of skin photosensitivity called erythropoietic protoporphyria (EPP), which is caused by the excessive production of protoporphyrin IX (PPIX) by erythrocytes. Controversial results have been reported regarding hematologic status and iron status of patients with EPP. We thoroughly explored these parameters in Fechm1Pas mutant mice of 3 different genetic backgrounds. FECH deficiency induced microcytic hypochromic anemia without ringed sideroblasts, little or no hemolysis, and no erythroid hyperplasia. Serum iron, ferritin, hepcidin mRNA, and Dcytb levels were normal. The homozygous Fechm1Pas mutant involved no tissue iron deficiency but showed a clear-cut redistribution of iron stores from peripheral tissues to the spleen, with a concomitant 2- to 3-fold increase in transferrin expression at the mRNA and the protein levels. Erythrocyte PPIX levels strongly correlated with serum transferrin levels. At all stages of differentiation in our study, transferrin receptor expression in bone marrow erythroid cells in Fech(m1Pas) was normal in mutant mice but not in patients with iron-deficiency anemia. Based on these observations, we suggest that oral iron therapy is not the therapy of choice for patients with EPP and that the PPIX-liver transferrin pathway plays a role in the orchestration of iron distribution between peripheral iron stores, the spleen, and the bone marrow.
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PMID:Increased plasma transferrin, altered body iron distribution, and microcytic hypochromic anemia in ferrochelatase-deficient mice. 1700 76

Erythropoietic protoporphyria is a disorder of heme synthesis in which deficient ferrochelatase activity leads to excess production and biliary excretion of protoporphyrin. The main clinical features, photosensitivity and hepatobiliary disease that may progress to liver failure, are caused by the toxicity of protoporphyrin. Liver transplantation has been used to treat liver failure in erythropoietic protoporphyria, but excess production of protoporphyrin by the bone marrow continues causing recurrence of liver disease in the majority of patients. This is the first report of successful sequential liver and bone marrow transplantation in a patient with liver failure as a result of erythropoietic protoporphyria. This combination corrected the severe phenotype, resolving the severe photosensitivity and halting erythropoietic protoporphyria associated liver graft injury. Splenectomy seemed to facilitate the successful bone marrow transplant.
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PMID:Sequential liver and bone marrow transplantation for treatment of erythropoietic protoporphyria. 1707 41


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