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- Metzendorf, Christoph, et al.
(författare)
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Drosophila mitoferrin is essential for male fertility : Evidence for a role of mitochondrial iron metabolism during spermatogenesis
- 2010
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Ingår i: BMC Developmental Biology. - 1471-213X. ; 10, s. 68-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Mammals and Drosophila melanogaster share some striking similarities in spermatogenesis. Mitochondria in spermatids undergo dramatic morphological changes and syncytial spermatids are stripped from their cytoplasm and then individually wrapped by single membranes in an individualization process. In mammalian and fruit fly testis, components of the mitochondrial iron metabolism are expressed, but so far their function during spermatogenesis is unknown. Here we investigate the role of Drosophila mitoferrin (dmfrn), which is a mitochondrial carrier protein with an established role in the mitochondrial iron metabolism, during spermatogenesis.Results: We found that P-element insertions into the 5'-untranslated region of the dmfrn gene cause recessive male sterility, which was rescued by a fluorescently tagged transgenic dmfrn genomic construct (dmfrn(venus)). Testes of mutant homozygous dmfrn(SH115) flies were either small with unorganized content or contained some partially elongated spermatids, or testes were of normal size but lacked mature sperm. Testis squashes indicated that spermatid elongation was defective and electron micrographs showed mitochondrial defects in elongated spermatids and indicated failed individualization. Using a LacZ reporter and the dmfrn(venus) transgene, we found that dmfrn expression in testes was highest in spermatids, coinciding with the stages that showed defects in the mutants. Dmfrn-venus protein accumulated in mitochondrial derivatives of spermatids, where it remained until most of it was stripped off during individualization and disposed of in waste bags. Male sterility in flies with the hypomorph alleles dmfrn(BG00456) and dmfrn(EY01302) over the deletion Df(3R)ED6277 was increased by dietary iron chelation and suppressed by iron supplementation of the food, while male sterility of dmfrn(SH115)/Df(3R)ED6277 flies was not affected by food iron levels.Conclusions: In this work, we show that mutations in the Drosophila mitoferrin gene result in male sterility caused by developmental defects. From the sensitivity of the hypomorph mutants to low food iron levels we conclude that mitochondrial iron is essential for spermatogenesis. This is the first time that a link between the mitochondrial iron metabolism and spermatogenesis has been shown. Furthermore, due to the similar expression patterns of some mitochondrial iron metabolism genes in Drosophila and mammals, it is likely that our results are applicable for mammals as well.
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| 2. |
- Metzendorf, Christoph, 1977-
(författare)
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Mitochondrial Iron Metabolism : Study of mitoferrin in Drosophila melanogaster
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 3. |
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| 4. |
- Metzendorf, Christoph, et al.
(författare)
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Mitoferrin is essential for normal development in Drosophila melanogaster
- 2013
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Konferensbidrag (refereegranskat)abstract
- Mitochondria are crucial to iron metabolism, being the unique site for heme synthesis and the major site for iron-sulfur (Fe-S) cluster biosynthesis. Iron is transported into the mitochondrion by an iron metal transporter, mitoferrin, in the inner membrane of mitochondria. By studying different dmfrn Drosophila mutants we have previously showed that dmfrn and mitochondrial iron metabolism have an important role during spermatogenesis and that a functional dmfrn is essential for male fertility (Metzendorf & Lind, 2010). During the spermatogenesis study, we characterized two fly strains with deletions in the dmfrn gene, which is located on the right arm of chromosome three. In the strain with the small deletion dmfrnDf13, which we recovered during P-element mobilization, a third of the 5´ untranslated region is deleted. In the strain Df(3R)ED6277, the genes dmfrn and CG5514 are deleted and half of the 5´ untranslated regions of genes Mes-4 and Gp93 are removed. We found that deletion of dmfrn, (homozygous dmfrnDf13, transheterozygous dmfrnDf13/Df(3R)ED6277 or homozygous Df(3R)ED6277) causes lethality at larval stage.In the current study we analyzed the developmental phenotype in further detail. As fertility of the hypomorph dmfrn P element mutant strains is depended on the level of dietary iron (Metzendorf & Lind, 2010), we were interested if the deletion mutants might show a similar dependence. Using a third chromosome balancer with markers, Tb (Tubby will result in shorter larvae and pupae) and Sb (stubble: bristles short and stubby) that allows distinguishing between heterozygous and transheterozygous flies at the larval, pupal and adult stage makes it possible to quantify the genotypes. We found that transheterozygous (dmfrnDf13/Df(3R)ED6277) flies develop to third instar larvae and very seldom start puparation (<0.25%) when the flies was fed with low iron food. On normal food, transheterozygous flies develop to the pupal stage (~17%), but very few flies eclose as adults (~6%). Knocking down dmfrn expression by Gal4/UAS driven RNA interference (RNAi) with a ubiquitous driver, resulted in a phenotype similar to that of the dmfrn deletion strains. Introduction of the genomic construct dmfrnvenusB32 (a fluorescently (venus) tagged transgenic dmfrn) rescued dmfrn deletion flies to pupal stage on low iron food, and increased the fraction of eclosed adults with the dmfrn deletion alleles on normal and high iron food. The presence of third instar larvae without the balancer indicates that dmfrn deletion might not cause larval lethality, but may either slow down development or cause developmental arrest. We concluded that mitoferrin is essential for normal development and that the developmental phenotype of mitoferrin deletion mutants can be rescued to some degree by addition of dietary iron, showing that the developmental lethality or arrest is due to mitochondrial iron deficiency.Metzendorf , C. and Lind M.I. (2010) Drosophila mitoferrin is essential for male fertility: evidence for a role of mitochondrial iron metabolism during spermatogenesis. BMC Developmental Biology, 10, 68.
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| 5. |
- Metzendorf, Christoph, et al.
(författare)
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The role of iron in the proliferation of Drosophila l(2)mbn cells
- 2010
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 400:3, s. 442-446
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Tidskriftsartikel (refereegranskat)abstract
- Iron is essential for life and is needed for cell proliferation and cell cycle progression. Iron deprivation induces cell cycle arrest and finally apoptosis. The Drosophila tumorous larval hemocyte cell line l(2)mbn was used to study the sensitivity and cellular response to iron deprivation through the chelator desferrioxamine (DFO). At a concentration of 10 mM DFO or more the proliferation was inhibited reversibly, while the amount of dead cells did not increase. FACS analysis showed that the cell cycle was arrested in G1/S phase and the transcript level of cycE was decreased to less than 50% of control cells. These results show that iron chelation in this insect tumorous cell line causes a specific and coordinated cell cycle arrest.
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