Studying stress-related epigenetic and metabolic changes in fruit flies and mice through monogenic and polygenic models

Venkatasubramani, Anuroop Venkateswaran (2024): Studying stress-related epigenetic and metabolic changes in fruit flies and mice through monogenic and polygenic models. Dissertation, LMU München: Medizinische Fakultät

Abstract

Epigenetic factors and metabolic intermediates have been at the forefront of chromatin research in the past few years. The communication between metabolic process and epigenetic factors with the genetic component is especially important to translate environmental changes to the organisms to either improve its survival in short term or provide the ability to adapt in the longer run. We studied these aspects using a poikilothermic species such as Drosophila melanogaster (Publication-1) and a higher organism, Mus musculus, which are more closely related to humans (Publication-2). In the first study, Venkatasubramani et al., 2023, we aimed to understand the evolutionary importance of chameau (chm), a MYST-domain acetyltransferase. We have previously shown that absence of this protein improves both physical activity and longevity in Drosophila melanogaster (Peleg, Feller, Forne, et al., 2016). We employed UAS-GAL4 system to knockdown the gene both ubiquitously and tissue-specifically. Upon observing massive physiological changes with ubiquitous, neuronal and fatbody loss of chm, we also confirmed the importance of MYST-domain, i.e. acetyltransferase activity, using a heterozygous mutant with a deletion of MYST genomic region that also showed similar observation. Following this, we used a multi-omics strategy to assess the effect of mutation (or knockdown) on transcriptome, histone acetylome, proteome and non-histone acetylome. Observations from these approaches pointed towards misregulated metabolism. We therefore tested the ability of organisms lacking the protein to respond to metabolic stress by administering wet-starvation and as expected, these flies showed reduced starvation resilience. Interestingly, this was independent of chm’s role in development as assessed using GeneSwitch system, where chm knockdown is induced in an adult-specific manner. Further, we also validated the perceived role of chm in metabolism and stress response by over-expressing the protein ubiquitously and in different tissues via the UAS-GAL4 system. All these experiments resulted in an improved survival upon metabolic stress and specifically upon over-expression in tissues such as neurons and fatbody. In addition, we have evidence that support this putative evolutionary role of chm in stress response is limited only to certain temperature ranges, which could be considered non-ideal for the organism. This is also supported by evidence of sequence variation and balancing selection in different climatic populations (Levine & Begun, 2008; Croze et al., 2017). This is being addressed in a follow-up study that is in preparation. The second study was a collaborative effort with Peleg lab. In this study, (Müller-Eigner et al., 2022), we characterized a unique and novel mouse model named Titan that has been selected for over 180 generations based on their high body mass. After assessing their genetic, biochemical and physiological status, we perceived that these mouse show similarities to metabolic syndrome in humans. We further compared Titan mice to unselected mice and characterized histone PTMs and subsequently proteome and transcriptome, all of which pointed towards metabolic differences. All these were assessed in two ages in unselected and Titan mouse as the latter also showed a steep decline in lifespan. Intriguingly, genetic analysis showed variation in acetyltransferase genes and accordingly, acetylation of H4 was altered between the mouse models. Finally, we employed dietary intervention, an intervention that may result in extended life span to test if these mice can display improved survival and rescue associated molecular changes. This study characterized and provided an additional animal model for studying metabolic diseases like obesity and showed the importance of having a non-inbred model that displays genetic variability. The study also provided an interesting take on reversing the possible effects of genetic differences via changes in lifestyle. Altogether, these studies provide an understanding of metabolic dysregulation in organisms, either upon mutation or phenotypic selection. In particular, the evolutionary importance and a previously unknown role of chm in metabolism of Drosophila melanogaster and the characterization of a long-term phenotypically selected Mus musculus model, Titan mice, as a novel and unique resource for studying metabolic disorders that closely reflects conditions in human.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Themengebiete: 600 Technik, Medizin, angewandte Wissenschaften ; 600 Technik, Medizin, angewandte Wissenschaften > 610 Medizin und Gesundheit
• Fakultäten: Medizinische Fakultät
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 16. Juli 2024
• 1. Bericht­erstatter:in: Imhof, Axel