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The yeast dynamin-like protein, Mgm1p, functions on the mitochondrial outer membrane to mediate mitochondrial inheritance.

Shepard KA, Yaffe MP - J. Cell Biol. (1999)

Bottom Line: It also caused aberrant mitochondrial distribution and morphology when expressed at high levels in cells that also contained a wild-type copy of the gene.Mgm1p was localized to the mitochondrial outer membrane and fractionated as a component of a high molecular weight complex.These results indicate that Mgm1p is a mitochondrial inheritance and morphology component that functions on the mitochondrial surface.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of California, San Diego, La Jolla, California 92093-0347, USA.

ABSTRACT
The mdm17 mutation causes temperature-dependent defects in mitochondrial inheritance, mitochondrial morphology, and the maintenance of mitochondrial DNA in the yeast Saccharomyces cerevisiae. Defects in mitochondrial transmission to daughter buds and changes in mitochondrial morphology were apparent within 30 min after shifting cells to 37 degrees C, while loss of the mitochondrial genome occurred after 4-24 h at the elevated temperature. The mdm17 lesion mapped to MGM1, a gene encoding a dynamin-like GTPase previously implicated in mitochondrial genome maintenance, and the cloned MGM1 gene complements all of the mdm17 mutant phenotypes. Cells with an mgm1- mutation displayed aberrant mitochondrial inheritance and morphology. A version of mgm1 mutated in a conserved residue in the putative GTP-binding site was unable to complement any of the mutant defects. It also caused aberrant mitochondrial distribution and morphology when expressed at high levels in cells that also contained a wild-type copy of the gene. Mgm1p was localized to the mitochondrial outer membrane and fractionated as a component of a high molecular weight complex. These results indicate that Mgm1p is a mitochondrial inheritance and morphology component that functions on the mitochondrial surface.

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Quantitation of mitochondrial inheritance, morphology, and respiration defects in mdm17 cells. Wild-type (MYY291) and  mdm17 (MYY972) cells were grown at 23°C, incubated at 37°C for 0, 1, 2, or 4 h, fixed, and processed for indirect immunofluorescence  microscopy. Mitochondria were visualized with antibodies against OM14, a mitochondrial outer membrane protein. To quantify the defects, at least 300 budded cells at each time were examined, and the percentages of cells displaying aggregated mitochondria (A) and  cells with buds devoid of mitochondria (B) were determined. (C) Wild-type (MYY291) and mdm17 (MYY972) cells were grown in glucose medium (YPD) at 37°C for 0, 1, 2, 4, 16, or 24 h, and plated onto YPD-agar plates. Cells were cultured at 23°C, colonies were replica plated to glycerol medium (YPG), and incubated at 23°C. The percentage of colonies that failed to grow on YPG was scored as having lost respiration competence.
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Figure 2: Quantitation of mitochondrial inheritance, morphology, and respiration defects in mdm17 cells. Wild-type (MYY291) and mdm17 (MYY972) cells were grown at 23°C, incubated at 37°C for 0, 1, 2, or 4 h, fixed, and processed for indirect immunofluorescence microscopy. Mitochondria were visualized with antibodies against OM14, a mitochondrial outer membrane protein. To quantify the defects, at least 300 budded cells at each time were examined, and the percentages of cells displaying aggregated mitochondria (A) and cells with buds devoid of mitochondria (B) were determined. (C) Wild-type (MYY291) and mdm17 (MYY972) cells were grown in glucose medium (YPD) at 37°C for 0, 1, 2, 4, 16, or 24 h, and plated onto YPD-agar plates. Cells were cultured at 23°C, colonies were replica plated to glycerol medium (YPG), and incubated at 23°C. The percentage of colonies that failed to grow on YPG was scored as having lost respiration competence.

Mentions: To examine the development of mutant phenotypes at 37°C, populations of mutant cells were analyzed by indirect immunofluorescence microscopy at various times after shifting to the nonpermissive temperature (Fig. 2, A and B). After 1 h at 37°C, most cells (87%) contained aggregated mitochondria, and a significant fraction of cells (18%) possessed buds devoid of mitochondria. Some of the cells with empty buds still possessed mitochondria with normal tubular morphology (data not shown). By 2 h, 90% of cells displayed aggregated mitochondria and a majority (56%) possessed empty buds. These results demonstrate that the mdm17 mutation rapidly causes defects in mitochondrial distribution and morphology after shifting cells to the nonpermissive temperature.


The yeast dynamin-like protein, Mgm1p, functions on the mitochondrial outer membrane to mediate mitochondrial inheritance.

Shepard KA, Yaffe MP - J. Cell Biol. (1999)

Quantitation of mitochondrial inheritance, morphology, and respiration defects in mdm17 cells. Wild-type (MYY291) and  mdm17 (MYY972) cells were grown at 23°C, incubated at 37°C for 0, 1, 2, or 4 h, fixed, and processed for indirect immunofluorescence  microscopy. Mitochondria were visualized with antibodies against OM14, a mitochondrial outer membrane protein. To quantify the defects, at least 300 budded cells at each time were examined, and the percentages of cells displaying aggregated mitochondria (A) and  cells with buds devoid of mitochondria (B) were determined. (C) Wild-type (MYY291) and mdm17 (MYY972) cells were grown in glucose medium (YPD) at 37°C for 0, 1, 2, 4, 16, or 24 h, and plated onto YPD-agar plates. Cells were cultured at 23°C, colonies were replica plated to glycerol medium (YPG), and incubated at 23°C. The percentage of colonies that failed to grow on YPG was scored as having lost respiration competence.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132935&req=5

Figure 2: Quantitation of mitochondrial inheritance, morphology, and respiration defects in mdm17 cells. Wild-type (MYY291) and mdm17 (MYY972) cells were grown at 23°C, incubated at 37°C for 0, 1, 2, or 4 h, fixed, and processed for indirect immunofluorescence microscopy. Mitochondria were visualized with antibodies against OM14, a mitochondrial outer membrane protein. To quantify the defects, at least 300 budded cells at each time were examined, and the percentages of cells displaying aggregated mitochondria (A) and cells with buds devoid of mitochondria (B) were determined. (C) Wild-type (MYY291) and mdm17 (MYY972) cells were grown in glucose medium (YPD) at 37°C for 0, 1, 2, 4, 16, or 24 h, and plated onto YPD-agar plates. Cells were cultured at 23°C, colonies were replica plated to glycerol medium (YPG), and incubated at 23°C. The percentage of colonies that failed to grow on YPG was scored as having lost respiration competence.
Mentions: To examine the development of mutant phenotypes at 37°C, populations of mutant cells were analyzed by indirect immunofluorescence microscopy at various times after shifting to the nonpermissive temperature (Fig. 2, A and B). After 1 h at 37°C, most cells (87%) contained aggregated mitochondria, and a significant fraction of cells (18%) possessed buds devoid of mitochondria. Some of the cells with empty buds still possessed mitochondria with normal tubular morphology (data not shown). By 2 h, 90% of cells displayed aggregated mitochondria and a majority (56%) possessed empty buds. These results demonstrate that the mdm17 mutation rapidly causes defects in mitochondrial distribution and morphology after shifting cells to the nonpermissive temperature.

Bottom Line: It also caused aberrant mitochondrial distribution and morphology when expressed at high levels in cells that also contained a wild-type copy of the gene.Mgm1p was localized to the mitochondrial outer membrane and fractionated as a component of a high molecular weight complex.These results indicate that Mgm1p is a mitochondrial inheritance and morphology component that functions on the mitochondrial surface.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of California, San Diego, La Jolla, California 92093-0347, USA.

ABSTRACT
The mdm17 mutation causes temperature-dependent defects in mitochondrial inheritance, mitochondrial morphology, and the maintenance of mitochondrial DNA in the yeast Saccharomyces cerevisiae. Defects in mitochondrial transmission to daughter buds and changes in mitochondrial morphology were apparent within 30 min after shifting cells to 37 degrees C, while loss of the mitochondrial genome occurred after 4-24 h at the elevated temperature. The mdm17 lesion mapped to MGM1, a gene encoding a dynamin-like GTPase previously implicated in mitochondrial genome maintenance, and the cloned MGM1 gene complements all of the mdm17 mutant phenotypes. Cells with an mgm1- mutation displayed aberrant mitochondrial inheritance and morphology. A version of mgm1 mutated in a conserved residue in the putative GTP-binding site was unable to complement any of the mutant defects. It also caused aberrant mitochondrial distribution and morphology when expressed at high levels in cells that also contained a wild-type copy of the gene. Mgm1p was localized to the mitochondrial outer membrane and fractionated as a component of a high molecular weight complex. These results indicate that Mgm1p is a mitochondrial inheritance and morphology component that functions on the mitochondrial surface.

Show MeSH
Related in: MedlinePlus