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The alternative oxidase AOX does not rescue the phenotype of tko25t mutant flies.

Kemppainen KK, Kemppainen E, Jacobs HT - G3 (Bethesda) (2014)

Bottom Line: AOX expression for 1 d after eclosion, or continuously throughout development, had no effect on the bang sensitivity of tko(25t) adults, and continued expression in adults older than 30 d also produced no amelioration of the phenotype.We conclude that AOX does not rescue tko(25t) and that the mutant phenotype is not solely due to limitations on electron flow in the respiratory chain, but rather to a more complex metabolic defect.The future therapeutic use of AOX in disorders of mitochondrial translation may thus be of limited value.

View Article: PubMed Central - PubMed

Affiliation: BioMediTech and Tampere University Hospital, FI-33014 University of Tampere, Tampere, Finland.

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Altered ATP and ROS levels do not account for phenotypic effects of AOX or Ndi1. Effects of Ndi1 and AOX expression on (A) ATP levels and (B) mitochondrial ROS production of female tko25t flies of the indicated genotypes, reared at 18°. Flies were homozygous for tko25t, except those carrying the FM7 balancer, which are phenotypically wild-type. Means ± SD for three or more biological replicates of each genotype.*Significant differences between tko25t homozygotes and heterozygotes of otherwise identical genotypes, P < 0.01, Student’s t test, two-tailed. #Significant differences between Ndi1 or AOX expressors and nonexpressors of otherwise identical genotypes, P < 0.05, Student’s t test, two-tailed.
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fig6: Altered ATP and ROS levels do not account for phenotypic effects of AOX or Ndi1. Effects of Ndi1 and AOX expression on (A) ATP levels and (B) mitochondrial ROS production of female tko25t flies of the indicated genotypes, reared at 18°. Flies were homozygous for tko25t, except those carrying the FM7 balancer, which are phenotypically wild-type. Means ± SD for three or more biological replicates of each genotype.*Significant differences between tko25t homozygotes and heterozygotes of otherwise identical genotypes, P < 0.01, Student’s t test, two-tailed. #Significant differences between Ndi1 or AOX expressors and nonexpressors of otherwise identical genotypes, P < 0.05, Student’s t test, two-tailed.

Mentions: We confirmed the previous observation of decreased ATP levels in tko25t homozygotes compared with heterozygous controls (Figure 6A) but found no significant alteration thereof when either AOX or Ndi1 was expressed. Mitochondrial ROS production in tko25t homozygotes was also elevated in every case compared with heterozygous controls (Figure 6B). This was unaffected by expression of AOX but modestly alleviated by Ndi1 expression, despite the fact that the effect of Ndi1 on the overall organismal phenotype was deleterious. This, plus the wide variation in ROS production according to genetic background (reflecting different balancer chromosomes), implies that the tko25t organismal phenotype is also not directly determined by ROS.


The alternative oxidase AOX does not rescue the phenotype of tko25t mutant flies.

Kemppainen KK, Kemppainen E, Jacobs HT - G3 (Bethesda) (2014)

Altered ATP and ROS levels do not account for phenotypic effects of AOX or Ndi1. Effects of Ndi1 and AOX expression on (A) ATP levels and (B) mitochondrial ROS production of female tko25t flies of the indicated genotypes, reared at 18°. Flies were homozygous for tko25t, except those carrying the FM7 balancer, which are phenotypically wild-type. Means ± SD for three or more biological replicates of each genotype.*Significant differences between tko25t homozygotes and heterozygotes of otherwise identical genotypes, P < 0.01, Student’s t test, two-tailed. #Significant differences between Ndi1 or AOX expressors and nonexpressors of otherwise identical genotypes, P < 0.05, Student’s t test, two-tailed.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4199707&req=5

fig6: Altered ATP and ROS levels do not account for phenotypic effects of AOX or Ndi1. Effects of Ndi1 and AOX expression on (A) ATP levels and (B) mitochondrial ROS production of female tko25t flies of the indicated genotypes, reared at 18°. Flies were homozygous for tko25t, except those carrying the FM7 balancer, which are phenotypically wild-type. Means ± SD for three or more biological replicates of each genotype.*Significant differences between tko25t homozygotes and heterozygotes of otherwise identical genotypes, P < 0.01, Student’s t test, two-tailed. #Significant differences between Ndi1 or AOX expressors and nonexpressors of otherwise identical genotypes, P < 0.05, Student’s t test, two-tailed.
Mentions: We confirmed the previous observation of decreased ATP levels in tko25t homozygotes compared with heterozygous controls (Figure 6A) but found no significant alteration thereof when either AOX or Ndi1 was expressed. Mitochondrial ROS production in tko25t homozygotes was also elevated in every case compared with heterozygous controls (Figure 6B). This was unaffected by expression of AOX but modestly alleviated by Ndi1 expression, despite the fact that the effect of Ndi1 on the overall organismal phenotype was deleterious. This, plus the wide variation in ROS production according to genetic background (reflecting different balancer chromosomes), implies that the tko25t organismal phenotype is also not directly determined by ROS.

Bottom Line: AOX expression for 1 d after eclosion, or continuously throughout development, had no effect on the bang sensitivity of tko(25t) adults, and continued expression in adults older than 30 d also produced no amelioration of the phenotype.We conclude that AOX does not rescue tko(25t) and that the mutant phenotype is not solely due to limitations on electron flow in the respiratory chain, but rather to a more complex metabolic defect.The future therapeutic use of AOX in disorders of mitochondrial translation may thus be of limited value.

View Article: PubMed Central - PubMed

Affiliation: BioMediTech and Tampere University Hospital, FI-33014 University of Tampere, Tampere, Finland.

Show MeSH
Related in: MedlinePlus