Proper mitochondrial function requires the coordinated expression of 37 genes encoded in the circular genome inside the mitochondrion, and over 1000 genes encoded on nuclear chromosomes. This intracellular, intergenomic communication presents a complicated network of interacting genes that are critical for the energy production that sustains life. Because each of these genes is variable in natural populations, each gene-by-gene interaction can be altered by the variation among individuals. Moreover, the mitochondrion is a hub of many signaling pathways that sense nutrients, oxygen, redox state of the cell, and temperature making it sensitive to environmental conditions. As a result, these interactions present a complex system that lies between genotype and phenotype.
The first Aim i s to map specific nuclear genes that interact with mtDNA-encoded genes that jointly cause developmental delay in Drosophila. The goals of the previous cycle of funding were to identify these `mitonuclear' interactions by replacing mtDNAs from D. melanogaster or D. simulans in to multiple strains of the Drosophila Genetics Reference Panel (DGRP). This goal has been achieved, so Aim 1 tests the hypotheses that DGRP strains causing developmental delays for all `foreign' Dsim-mtDNAs harbor multiple `mitonuclear genes' affecting development, while DGRP strains causing delays for single-mtDNAs harbor single-factor mitonuclear genes.
The second Aim will identify the mutations in these genes and test their direct function using transgenic rescue experiments. A second goal of the previous funding period was to determine the genotype-by-environment (GxE) interactions for mitonuclear genotypes by exposing them to altered diets. We have determined that strong mitonuclear interactions in the DGRP can be eliminated by altering the protein content of the diet. Thus, The third Aim tests the hypothesis that the mitonuclear epistatic partners affecting development time are the loci responsible for dietary modification of this trait, vs. other trans-acting factors. Gene-by-gene (GxG) and GxE interactions are fundamental components of complex phenotypes, but the mechanistic bases of these interactions are poorly understood. Because most genome wide association studies (GWAS) do not test for mtDNA or joint mitonuclear interaction effects on phenotype, our proposed experiments address this shortcoming directly, and may identify factors underlying `missing heritability' not identified in GWAS. The research is relevant to the genetic interactions important in mitochondrial replacement therapies and the biochemical pathways affecting obesity and metabolic syndromes. By manipulating dietary environments, we may identify novel roles for mitonuclear interactions relevant to pharmaceutical treatments of these conditions.

Public Health Relevance

Mitochondrial dysfunction is a leading cause of metabolic disease, affecting 1 in ~5000 individuals and this high incidence of disease is likely due to the complex genomic basis of mitochondrial function, which requires coordinated expression of 37 genes in the mitochondrial genome (mtDNA) and more than 1000 genes in the nuclear genome. This project will dissect the joint contribution of mtDNA- and nuclear-encoded genes to developmental delay in Drosophila and determine how dietary modifications can rescue or exacerbate this delay. These experiments will provide information about the genetic basis of mitochondrial function for pathways related to obesity and metabolic syndromes, and may contribute to our understanding of the genetics of mitochondrial replacement therapy and the development of pharmaceuticals that compensate for reduced mitochondrial function.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM067862-14
Application #
9419309
Study Section
Genetic Variation and Evolution Study Section (GVE)
Program Officer
Krasnewich, Donna M
Project Start
2004-08-01
Project End
2021-03-31
Budget Start
2018-04-01
Budget End
2019-03-31
Support Year
14
Fiscal Year
2018
Total Cost
Indirect Cost
Name
Brown University
Department
Biology
Type
Schools of Medicine
DUNS #
001785542
City
Providence
State
RI
Country
United States
Zip Code
Buchanan, Justin L; Meiklejohn, Colin D; Montooth, Kristi L (2018) Mitochondrial Dysfunction and Infection Generate Immunity-Fecundity Tradeoffs in Drosophila. Integr Comp Biol 58:591-603
Sujkowski, Alyson; Spierer, Adam N; Rajagopalan, Thiviya et al. (2018) Mito-nuclear interactions modify Drosophila exercise performance. Mitochondrion :
Rand, David M; Mossman, Jim A; Zhu, Lei et al. (2018) Mitonuclear epistasis, genotype-by-environment interactions, and personalized genomics of complex traits in Drosophila. IUBMB Life 70:1275-1288
Rand, David M (2017) Fishing for adaptive epistasis using mitonuclear interactions. PLoS Genet 13:e1006662
Mossman, Jim A; Tross, Jennifer G; Jourjine, Nick A et al. (2017) Mitonuclear Interactions Mediate Transcriptional Responses to Hypoxia in Drosophila. Mol Biol Evol 34:447-466
Mossman, Jim A; Tross, Jennifer G; Li, Nan et al. (2016) Mitochondrial-Nuclear Interactions Mediate Sex-Specific Transcriptional Profiles in Drosophila. Genetics 204:613-630
Mossman, Jim A; Biancani, Leann M; Zhu, Chen-Tseh et al. (2016) Mitonuclear Epistasis for Development Time and Its Modification by Diet in Drosophila. Genetics 203:463-84
Holmbeck, Marissa A; Rand, David M (2015) Dietary Fatty Acids and Temperature Modulate Mitochondrial Function and Longevity in Drosophila. J Gerontol A Biol Sci Med Sci 70:1343-54
Holmbeck, Marissa A; Donner, Julia R; Villa-Cuesta, Eugenia et al. (2015) A Drosophila model for mito-nuclear diseases generated by an incompatible interaction between tRNA and tRNA synthetase. Dis Model Mech 8:843-54
Villa-Cuesta, Eugenia; Rand, David M (2015) Preparation of Mitochondrial Enriched Fractions for Metabolic Analysis in Drosophila. J Vis Exp :

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