Nuclear Genome-Encoded Mitochondrial OXPHOS Complex I Genes in Female Buffalo Show Tissue-Specific Differences

Effect of glutathione addition on vitrification of ovine oocytes

The exogenous antioxidants are commonly employed to mitigate vitrification-induced oxidative damage. Glutathione (GSH), a vital antioxidant, plays a significant role in scavenging free radicals, providing antioxidant protection, and maintaining cellular integrity. This study aimed to investigate the effects of GSH supplementation on the vitrification of ovine oocytes. To identify the optimal concentration of exogenous GSH supplementation, the impacts of 2 mM, 4 mM, and 8 mM GSH on the survival and fragmentation of oocytes were evaluated after vitrification. In addition, immunofluorescence (IF) staining was employed to evaluate spindle morphology, chromosome distribution, cortical granule distribution, mitochondrial function, and reactive oxygen species (ROS) levels. The levels of ATP and NADPH, along with the ratio of GSH/GSSH, were also examined. Additionally, evaluations of in vitro fertilization were carried out. The results of oocyte survival rates and fragmentation rates identified that the addition of 4 mM GSH to the vitrification solution was the optimal concentration. The assessment of spindle morphology, chromosome distribution, cortical granule distribution, mitochondrial function, ROS production, ATP activity, and NADPH levels, as well as the GSH/GSSH ratio, confirm the beneficial effect of GSH supplementation against the vitrification-induced oxidative damage. Lastly, incorporating GSH into the vitrification process enhanced the developmental potential of oocytes, resulting in higher cleavage rates, increased blastocyst rates, and improved quality of blastocysts. Overall, this research uncovered the mechanisms through which GSH mitigates the oxidative damage induced by vitrification, thereby leading to the optimization of the vitrification technique for ovine oocytes.

Unveiling the tissue-specific landscape of nuclear-encoded mitochondrial genes involved in amino acid metabolism in buffalo

Mitochondria play a pivotal role in energy production, metabolism, and cellular signaling, serving as key regulators of cellular functions, including differentiation and tissue-specific adaptation. The interplay between mitochondria and the nucleus is crucial for coordinating these processes, particularly through the supply of metabolites for epigenetic modifications that facilitate nuclear-mitochondrial interactions. To investigate tissue-specific mitochondrial adaptations at the molecular level, we conducted RNA sequencing data analyses of kidney, heart, brain, and ovary tissues of female buffaloes, focusing on variations in mitochondrial gene expression related to amino acid metabolism. Our analysis identified 82 nuclear-encoded mitochondrial transcripts involved in amino acid metabolism, with significant differential expression patterns across all tissues. Notably, the heart, brain, and kidney-tissues with higher energy demands-exhibited elevated expression levels compared to the ovary. The kidney displayed unique gene expression patterns, characterized by up-regulation of genes involved in glyoxylate metabolism and amino acid catabolism. In contrast, comparative analysis of the heart and kidney versus the brain revealed shared up-regulation of genes associated with fatty acid oxidation. Gene ontology and KEGG pathway analyses confirmed the enrichment of genes in pathways related to amino acid degradation and metabolism. These findings highlight the tissue-specific regulation of mitochondrial gene expression linked to amino acid metabolism, reflecting mitochondrial adaptations to the distinct metabolic and energy requirements of different tissues in buffalo. Importantly, our results underscore the relevance of mitochondrial adaptations not only for livestock health but also for understanding metabolic disorders in humans. By elucidating the molecular mechanisms of mitochondrial function and their tissue-specific variations, this study provides insights that could inform breeding strategies for enhanced livestock productivity and contribute to therapeutic approaches for human metabolic diseases. Thus, our findings illustrate how mitochondria are specialized in a tissue-specific manner to optimize amino acid utilization and maintain cellular homeostasis, with implications for both animal welfare and human health.

Differential expression of nuclear-derived mitochondrial succinate dehydrogenase genes in metabolically active buffalo tissues

BACKGROUND

Buffaloes are crucial to agriculture, yet mitochondrial biology in these animals is less studied compared to humans and laboratory animals. This research examines tissue-specific variations in mitochondrial succinate dehydrogenase (SDH) gene expression across buffalo kidneys, hearts, brains, and ovaries. Understanding these variations sheds light on mitochondrial energy metabolism and its impact on buffalo health and productivity, revealing insights into enzyme regulation and potential improvements in livestock management.

MATERIALS AND METHODS

RNA-seq data from buffalo kidney, heart, brain, and ovary tissues were reanalyzed to explore mitochondrial SDH gene expression. The expression of SDH subunits (SDHA, SDHB, SDHC, SDHD) and assembly factors (SDHAF1, SDHAF2, SDHAF3, SDHAF4) was assessed using a log2 fold-change threshold of + 1 for up-regulated and - 1 for down-regulated transcripts, with significance set at p < 0.05. Hierarchical clustering and differential expression analyses were performed to identify tissue-specific expression patterns and regulatory mechanisms, while Gene Ontology and KEGG pathway analyses were conducted to uncover functional attributes and pathway enrichments across different tissues.

RESULTS

Reanalysis of RNA-seq data from different tissues of healthy female buffaloes revealed distinct expression patterns for SDH subunits and assembly factors. While SDHA, SDHB, and SDHC showed variable expression across tissues, SDHAF2, SDHAF3, and SDHAF4 exhibited tissue-specific profiles. Significant up-regulation of SDHA, SDHB, and several assembly factors was observed in specific tissue comparisons, with fewer down-regulated transcripts. Gene ontology and KEGG pathway analyses linked the up-regulated transcripts to mitochondrial ATP synthesis and the respiratory electron transport chain. Notably, tissue-specific variations in mitochondrial function were particularly evident in the ovary.

CONCLUSION

This study identifies distinct SDH gene expression patterns in buffalo tissues, highlighting significant down-regulation of SDHA, SDHB, SDHC, and assembly factors in the ovary. These findings underscore the critical role of mitochondria in tissue-specific energy production and metabolic regulation, suggest potential metabolic adaptations, and emphasize the importance of mitochondrial complex II. The insights gained offer valuable implications for improving feed efficiency and guiding future research and therapies for energy metabolism disorders.

Deciphering tissue-specific expression profiles of mitochondrial genome-encoded tRNAs and rRNAs through transcriptomic profiling in buffalo

BACKGROUND

Mitochondria, essential for cellular energy production through oxidative phosphorylation (OXPHOS), integrate mt-DNA and nuclear-encoded genes. This cooperation extends to the mitochondrial translation machinery, involving crucial mtDNA-encoded RNAs: 22 tRNAs (mt-tRNAs) as adapters and two rRNAs (mt-rRNAs) for ribosomal assembly, enabling mitochondrial-encoded mRNA translation. Disruptions in mitochondrial gene expression can strongly impact energy generation and overall animal health. Our study investigates the tissue-specific expression patterns of mt-tRNAs and mt-rRNAs in buffalo.

MATERIAL AND METHODS

To investigate the expression patterns of mt-tRNAs and mt-rRNAs in different tissues and gain a better understanding of tissue-specific variations, RNA-seq was performed on various tissues, such as the kidney, heart, brain, and ovary, from post-pubertal female buffaloes. Subsequently, we identified transcripts that were differentially expressed in various tissue comparisons.

RESULTS

The findings reveal distinct expression patterns among specific mt-tRNA and mt-rRNA genes across various tissues, with some exhibiting significant upregulation and others demonstrating marked downregulation in specific tissue contexts. These identified variations reflect tissue-specific physiological roles, underscoring their significance in meeting the unique energy demands of each tissue. Notably, the brain exhibits the highest mtDNA copy numbers and an abundance of mitochondrial mRNAs of our earlier findings, potentially linked to the significant upregulation of mt-tRNAs in brain. This suggests a plausible association between mtDNA replication and the regulation of mtDNA gene expression.

CONCLUSION

Overall, our study unveils the tissue-specific expression of mitochondrial-encoded non-coding RNAs in buffalo. As we proceed, our further investigations into tissue-specific mitochondrial proteomics and microRNA studies aim to elucidate the intricate mechanisms within mitochondria, contributing to tissue-specific mitochondrial attributes. This research holds promise to elucidate the critical role of mitochondria in animal health and disease.