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Characterization of Drosophila mitoferrin and CG18317 mutants
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Comparative Physiology. (Maria Lind Karlberg)
Department of Applied Genetics and Cell Biology University of Natural Resources and Applied Life Sciences (BOKU) Muthgasse 18 1190 Vienna Austria.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Comparative Physiology. (Maria Lind Karlberg)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Introduction: Mitochondria are the site of iron-sulfur cluster synthesis and insertion of iron into heme, two essential prosthetic groups. Mrs3/4/mitoferrins are mitochondrial carrier proteins, which are involved in the mitochondrial iron transport. Yeast mutants suggest that a low-affinity iron transport system exists. Previous analysis of Drosophila mitoferrin P element mutants revealed an involvement of dmfrn in spermatogenesis. The ubiquitous expression of dmfrn in several adult male tissues, did however suggest a more general role.

Results: Here we analyzed stocks with deletions in dmfrn and find that on low iron food dmfrn deletion inhibits development to adulthood, whereas on normal and high iron food some escapers do eclose. RNAi of dmfrn driven by the ubiquitous Actin5C-Gal4 driver recapitulates the phenotype on low iron food, but not on normal or high iron food. Overexpression of dmfrn from an UAS-dmfrn transgenic construct that contains only the coding region of dmfrn also resulted in the failure to develop to adulthood on low iron food. We identified CG18317 as putative Drosophila homolog of yeast Rim2p/Mrs12p, a mitochondrial pyrimidine carrier that is implicated in low affinity iron transport. CG18317 is ubiquitously expressed in several tissues of the male fly and the second exon is alternatively spliced resulting in a 21 nucleotides shorter transcript. An initial study of transposon mutants and deletion mutants of this gene showed sensitivity of one transposon mutant to low iron food conditions. Preliminary results indicate that increased expression of CG18317 might rescue development of dmfrn deletion mutants to at least pupal stage.

Conclusions: In contrast to yeast MRS3/4, Drosophila mitoferrin is an essential gene, necessary for development of Drosophila to adulthood. The presence of escapers does however suggest, that dmfrn is either not the only mitochondrial iron carrier or that dmfrn modulates activity of a mitochondrial iron transport system. The sensitivity to low iron conditions of one CG18317 mutant and the partial rescue of dmfrn mutants indicates that this gene could indeed mediate mitochondrial iron uptake in the fly.

Keyword [en]
mitoferrin, Drosophila, iron, mitochondria, MRS12
National Category
Biological Sciences
Research subject
Biology with specialization in Comparative Physiology
Identifiers
URN: urn:nbn:se:uu:diva-114192OAI: oai:DiVA.org:uu-114192DiVA: diva2:293438
Available from: 2010-02-11 Created: 2010-02-11 Last updated: 2010-02-11
In thesis
1. Mitochondrial Iron Metabolism: Study of mitoferrin in Drosophila melanogaster
Open this publication in new window or tab >>Mitochondrial Iron Metabolism: Study of mitoferrin in Drosophila melanogaster
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Iron has a dualistic character. On the one hand it is essential for the life of most organisms, on the other hand it is involved in the generation of reactive oxygen species that are implicated in diseases and aging. During evolution efficient mechanisms for uptake, handling and storage of iron in a safe way have developed to keep the balance between iron availability and minimizing the hazards. In eukaryotes, mitochondria are the central organelle for “metabolizing” iron and consequently play an important role in cellular iron homeostasis.

Mitoferrins are mitochondrial carrier proteins, which are involved in iron transport into mitochondria. In vertebrates two mitoferrins exist, one (mitoferrin1) of which is essential for heme synthesis during erythropoiesis, while the function of the other (mitoferrin2) is not well defined. In the fruit fly we found only one mitoferrin gene (dmfrn), which codes most likely for a functional homologueof vertebrate mitoferrin2.

In Drosophila cell culture, dmfrn overexpression resulted in an overestimation of cell sensed iron levels. The signal responsible for this, is most likely a yet unidentified compound of ISC synthesis. In the cell culture system we also showed that iron chelation blocks the progression of the cell cycle in a reversible and therefore most likely controlled way.

Study of different dmfrn mutants indicates a role of dmfrn during spermatogenesis and development to adulthood. As dmfrn deletion mutants are not lethal, it is likely that other lower affinity iron transporters exist. A similar conclusion has been drawn by others from the study of yeast mitoferrin homologuemutants. Rim2p/Mrs12p has recently been implicated in mitochondrial iron transport, and might be an alternative metal carrier. We identified a putative homologuein the fruit fly and found a possible link between mutants in this gene and iron.

Our results emphasize the importance of the mitochondrial iron metabolism in cellular iron homeostasis. We also show for the first time, a direct connection between the mitochondrial iron metabolism and spermatogenesis. Mutants characterized and developed by us will help to study these processes in further detail and reveal the underlying mechanisms.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 55 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 713
Keyword
iron, Drosophila, mitochondria, mitoferrin, ferritin, spermatogenesis, cell cycle, DFO, MRS12
National Category
Biochemistry and Molecular Biology
Research subject
Biology with specialization in Comparative Physiology
Identifiers
urn:nbn:se:uu:diva-114201 (URN)978-91-554-7722-6 (ISBN)
Public defence
2010-03-25, Lindahlsalen, Evolutionary Biology Centre, Norbyvägen 18A, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2010-03-03 Created: 2010-02-11 Last updated: 2010-03-03Bibliographically approved

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Metzendorf, ChristophLind, Maria I.

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