Genetic architecture of heart mitochondrial proteome influencing cardiac hypertrophy
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eLife assessment
This paper demonstrates the genetic architecture of heart mitochondrial proteome that influences cardiac hypertrophy, using a panel of inbred mouse strains called the Hybrid Mouse Diversity Panel (HMDP). The HDM panel is a very powerful tool to study the genetic basis of various physiological and pathological processes in mice. The authors have used this panel extensively before, and in this paper, they extend their proteomic studies to demonstrate the genetic basis of cardiac hypertrophy. The studies will allow us to better understand the genetics of hypertrophic cardiomyopathy.
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Abstract
Mitochondria play an important role in both normal heart function and disease etiology. We report analysis of common genetic variations contributing to mitochondrial and heart functions using an integrative proteomics approach in a panel of inbred mouse strains called the Hybrid Mouse Diversity Panel (HMDP). We performed a whole heart proteome study in the HMDP (72 strains, n=2-3 mice) and retrieved 848 mitochondrial proteins (quantified in ≥50 strains). High-resolution association mapping on their relative abundance levels revealed three trans -acting genetic loci on chromosomes (chr) 7, 13 and 17 that regulate distinct classes of mitochondrial proteins as well as cardiac hypertrophy. DAVID enrichment analyses of genes regulated by each of the loci revealed that the chr13 locus was highly enriched for complex-I proteins (24 proteins, P =2.2E-61), the chr17 locus for mitochondrial ribonucleoprotein complex (17 proteins, P =3.1E-25) and the chr7 locus for ubiquinone biosynthesis (3 proteins, P =6.9E-05). Follow-up high resolution regional mapping identified NDUFS4, LRPPRC and COQ7 as the candidate genes for chr13, chr17 and chr7 loci, respectively, and both experimental and statistical analyses supported their causal roles. Furthermore, a large cohort of Diversity Outbred mice was used to corroborate Lrpprc gene as a driver of mitochondrial DNA (mtDNA)-encoded gene regulation, and to show that the chr17 locus is specific to heart. Variations in all three loci were associated with heart mass in at least one of two independent heart stress models, namely, isoproterenol-induced heart failure and diet-induced obesity. These findings suggest that common variations in certain mitochondrial proteins can act in trans to influence tissue-specific mitochondrial functions and contribute to heart hypertrophy, elucidating mechanisms that may underlie genetic susceptibility to heart failure in human populations.
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eLife assessment
This paper demonstrates the genetic architecture of heart mitochondrial proteome that influences cardiac hypertrophy, using a panel of inbred mouse strains called the Hybrid Mouse Diversity Panel (HMDP). The HDM panel is a very powerful tool to study the genetic basis of various physiological and pathological processes in mice. The authors have used this panel extensively before, and in this paper, they extend their proteomic studies to demonstrate the genetic basis of cardiac hypertrophy. The studies will allow us to better understand the genetics of hypertrophic cardiomyopathy.
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Reviewer #1 (Public Review):
In this paper, Krishnan et al. describe their findings on the genetic architecture of the heart mitochondrial proteome that influences cardiac hypertrophy. They analyzed common genetic variations contributing to mitochondrial and heart functions in a panel of inbred mouse strains called the Hybrid Mouse Diversity Panel (HMDP), by performing whole heart proteomics. The authors have published a number of papers on this panel, which appears to be a powerful system to study various genetic factors. They identified three trans-acting genetic loci, located on chromosome (chr) 7, chr13, and chr17, which control both mitochondrial proteins and heart hypertrophy. High-resolution regional mapping identified NDUFS4, LRPPRC, and COQ7 as the candidate genes for chr13, chr17, and chr7 loci, and variations of these genes …
Reviewer #1 (Public Review):
In this paper, Krishnan et al. describe their findings on the genetic architecture of the heart mitochondrial proteome that influences cardiac hypertrophy. They analyzed common genetic variations contributing to mitochondrial and heart functions in a panel of inbred mouse strains called the Hybrid Mouse Diversity Panel (HMDP), by performing whole heart proteomics. The authors have published a number of papers on this panel, which appears to be a powerful system to study various genetic factors. They identified three trans-acting genetic loci, located on chromosome (chr) 7, chr13, and chr17, which control both mitochondrial proteins and heart hypertrophy. High-resolution regional mapping identified NDUFS4, LRPPRC, and COQ7 as the candidate genes for chr13, chr17, and chr7 loci, and variations of these genes were associated with heart mass in isoproterenol-induced heart failure and diet-induced obesity. Using co-expression protein networks using weighted gene co-expression network analysis (WGCNA), they show that the chr13 locus was highly enriched for complex-I proteins, the chr17 locus for mitochondrial ribonucleoprotein complex, and the chr7 locus for ubiquinone biosynthesis. They concluded that "common variations of certain mitochondrial proteins can act in trans to influence mitochondrial functions and contribute to heart hypertrophy, elucidating mechanisms that may underlie genetic susceptibility to heart failure in human populations."
Although these studies are interesting and provide novel findings in the genetics of cardiac hypertrophy, there are a number of technical and conceptual issues that need to be addressed.
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Reviewer #2 (Public Review):
Krishnan, et al describe a unique and powerful approach to assessing the role of genetic variation on mitochondrial and cardiac function and health. Utilizing a panel of inbred mouse strains, on which they performed proteomics on heart samples, they measured 840 mitochondrial proteins and correlated these data to heart function using two heart stress models. This resulted in a number of correlative observations, three of which were explored in more detail to connect three specific genes to cardiac hypertrophy. This is an interesting dataset and there is clearly value in what is presented. The data were largely correlative, however, and there are only a couple of causation-oriented experiments. It's hard to adjudicate between these strengths and weaknesses in determining the overall impact of the manuscript.
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Reviewer #3 (Public Review):
The goal of this study is to identify mitochondrial pathways that would have an impact on the process of pathological cardiac hypertrophy. The paper presents a state-of-the-art analysis of the SNP variant and regulatory hot spots associated with quantitative traits, here mitochondrial protein levels and cardiac hypertrophy, using the Hybrid Mouse Diversity Panel. They identify 3 hotspots of trans-acting genetic loci that correlate with the level of proteins involved in complex I assembly, mitochondrial mRNA stability, and CoQ synthesis.
The study is overall very interesting and brings valuable information to the field. However, the impact of each of these loci on cardiac hypertrophy level, even if statistically significant, seems to be rather limited raising questions on the clinical relevance of the …
Reviewer #3 (Public Review):
The goal of this study is to identify mitochondrial pathways that would have an impact on the process of pathological cardiac hypertrophy. The paper presents a state-of-the-art analysis of the SNP variant and regulatory hot spots associated with quantitative traits, here mitochondrial protein levels and cardiac hypertrophy, using the Hybrid Mouse Diversity Panel. They identify 3 hotspots of trans-acting genetic loci that correlate with the level of proteins involved in complex I assembly, mitochondrial mRNA stability, and CoQ synthesis.
The study is overall very interesting and brings valuable information to the field. However, the impact of each of these loci on cardiac hypertrophy level, even if statistically significant, seems to be rather limited raising questions on the clinical relevance of the findings. It is an interesting study anyway and points to pathways that will deserve to be further explored in the future in clinical studies on human patients.
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