Related Experiment Video
Updated: Mar 8, 2026
Author Spotlight: Tracing the Ferroptotic Signatures and Cell Death Dynamics in Medulloblastoma for Advanced Therapeutics
Published on: March 15, 2024
Modeling the ferrochelatase c.315-48C modifier mutation for erythropoietic protoporphyria (EPP) in mice
Jasmin Barman-Aksözen1, Paulina C Wiek2, Vijay B Bansode2
1Institute of Laboratory Medicine, Municipal Hospital Triemli, Zürich 8063, Switzerland.
Abstract:
Erythropoietic protoporphyria (EPP) is caused by deficiency of ferrochelatase (FECH), which incorporates iron into protoporphyrin IX (PPIX) to form heme. Excitation of accumulated PPIX by light generates oxygen radicals that evoke excessive pain and, after longer light exposure, cause ulcerations in exposed skin areas of individuals with EPP. Moreover, ∼5% of the patients develop a liver dysfunction as a result of PPIX accumulation. Most patients (∼97%) have a severe FECH mutation (Mut) in trans to an intronic polymorphism (c.315-48C), which reduces ferrochelatase synthesis by stimulating the use of an aberrant 3' splice site 63 nt upstream of the normal site for exon 4. In contrast, with the predominant c.315-48T allele, the correct splice site is mostly used, and individuals with a T/Mut genotype do not develop EPP symptoms. Thus, the C allele is a potential target for therapeutic approaches that modify this splicing decision. To provide a model for pre-clinical studies of such approaches, we engineered a mouse containing a partly humanized Fech gene with the c.315-48C polymorphism. F1 hybrids obtained by crossing these mice with another inbred line carrying a severe Fech mutation (named m1Pas) show a very strong EPP phenotype that includes elevated PPIX in the blood, enlargement of liver and spleen, anemia, as well as strong pain reactions and skin lesions after a short period of light exposure. In addition to the expected use of the aberrant splice site, the mice also show a strong skipping of the partly humanized exon 3. This will limit the use of this model for certain applications and illustrates that engineering of a hybrid gene may have unforeseeable consequences on its splicing.
Insights
Erythropoietic protoporphyria (EPP) is a genetic disorder caused by ferrochelatase deficiency. Researchers developed a mouse model to study potential therapies targeting the c.315-48C splicing defect.
Area of Science:
- Biochemistry
- Genetics
- Medical Science
Background:
- Erythropoietic protoporphyria (EPP) results from ferrochelatase (FECH) deficiency, leading to protoporphyrin IX (PPIX) accumulation.
- Light exposure triggers oxygen radicals from PPIX, causing pain, skin ulcerations, and potential liver dysfunction in EPP patients.
- A common EPP genetic factor involves a severe FECH mutation with the c.315-48C intronic polymorphism, which disrupts correct splicing and FECH synthesis.
Purpose of the Study:
- To develop a preclinical model for evaluating therapeutic strategies targeting the c.315-48C splicing defect in EPP.
- To engineer a mouse model with a partly humanized Fech gene incorporating the c.315-48C polymorphism.
Main Methods:
- Created a mouse model with a partly humanized Fech gene carrying the c.315-48C polymorphism.
- Crossed these engineered mice with mice carrying a severe Fech mutation (m1Pas) to generate F1 hybrids.
- Analyzed the resulting EPP phenotype, including PPIX levels, organomegaly, anemia, and light sensitivity.
Main Results:
- F1 hybrids exhibited a severe EPP phenotype, including elevated blood PPIX, enlarged liver and spleen, anemia, and pronounced pain and skin lesions upon light exposure.
- Observed aberrant splicing at the targeted c.315-48C site, as expected.
- Detected significant skipping of the partly humanized exon 3, an unforeseen splicing consequence.
Conclusions:
- The engineered mouse model effectively recapitulates key features of human EPP, serving as a valuable tool for preclinical research.
- The unintended exon skipping highlights the complexity of gene engineering and potential challenges in predicting splicing outcomes.
- This model provides a foundation for developing and testing therapies aimed at correcting the splicing defect in EPP.
