Report

Teaser, summary, work performed and final results

Periodic Reporting for period 3 - NoisyAgeing (Beyond genotype to phenotype: how ancestor lifestyle impacts on lifespan variation in descendants)

Teaser

The discovery that genes control longevity has been quite significant for the understanding of ageing because it changed the view from a gradual stochastic process, to a genetically controlled process that we can interfere with and potentially slow down. Since then, thousands...

Summary

The discovery that genes control longevity has been quite significant for the understanding of ageing because it changed the view from a gradual stochastic process, to a genetically controlled process that we can interfere with and potentially slow down. Since then, thousands of genes and conditions have been found to influence lifespan, with many of them controlling the way in which organisms deal with external challenges brought by stress and nutrition. Such findings underscore that key interplay between genes and the environment and may explain the high degree of discordance among identical twins. Our lab’s interest is to understand the non-genetic influences on lifespan and stress related phenotypes using genetically identical lab strains of C.elegans as a model organism.
Our overarching aim is to use C. elegans to understand the significance of non-genetically encoded variability in the expression of genes that respond to external cues such as temperature and nutrients. We are interested in finding how early molecular differences in the way worms respond to stress can influence and be predictive of lifespan.

Others and I have shown that inter-individual variability in the longevity pathways –and in particular, in stress response genes- has consequences for genetic/environmental phenotypic robustness as well as for lifespan in Caenorhabditis elegans. The main goal of this proposal is to uncover the causes that explain inter-individual variability and the consequences for fitness related phenotypes. The variability across individuals must include an important non-genetic component because the laboratory strains of this nematode are genetically homogeneous. We propose that lifespan variation is a by-product of non-genetic sources of variability in the pathways that control longevity.

The overall objectives of this project are:
• Aim 1: To use High Throughput (HT) techniques to survey inter-individual variability of longevity related transcripts.
• Aim 2: To find environmental triggers behind transgenerational inheritance of lifespan and study whether they introduce inter-individual variability in gene expression.
• Aim 3: To uncover the molecular causes of inter-individual variability. The output of Aims 1 and 2 are transcripts that vary across individuals.
• Aim 4 : To optimise in silico methodologies to study metabolic fluxes applied to metabolic heterogeneity in C. elegans.

Work performed

\"1. In order to perform an analysis of inter-individual variability in gene expression, we have optimised a novel method for high throughput detection of inter-individual variability in C. elegans gene expression. This aim has given rise to two publications:
• \"\"Autophagy compensates for defects in mitochondrial dynamics\"\" Haeussler, S; Köhler, F; Premm, F; Rolland, S; Witting, M; Fischer, C; Chauve, L; Casanueva, O; Conradt, B. Accepted in Plos Genetics, 2020
• \"\"A protocol for high-throughput quantitative RT-qPCR in single C. elegans using nanofluidic technology\"\" Chauve L, Le Pen J, Hodge F, Todtenhaupt P, Biggins L, Miska E, Andrews S and Casanueva. Under revision at JOVE.

2. Optimisation of this method in conjunction to qPCR Bayes as a statistical method to measure biological variability from qPCR data. We have found that heat shock protein transcripts are variable and only expressed in neurons,
with consequences for stress survival.
“Inter individual variability in neuronal stress creates phenotypic heterogeneity in C. elegans” Chauve L, Vallejo C, Murdoch S, Todtenhaupt P, Biggins L, Marioni J, Casanueva, O. Manuscript in preparation.

3. Neuronal stress, in addition to influencing peripheral stress responses has a key effect on fat metabolism. We have discovered that the over-expression of the master regulator of the conserved heat shock response (HSR), Hsf-1, in head neurons, causes extensive fat remodelling to occur across tissues.
These changes include a a shift in the levels of unsaturated fatty acids in the plasma membrane. These data suggest that the activation of the HSR in neurons causes cell non-autonomous changes that are in line with ectothermic adaptive responses.
We have identified the cGMP receptor, TAX-2/TAX-4, as well as TGF-β/BMP signalling, as key players in signalling neuronal hsf-1 activity to peripheral tissues.
We also find that subtle, gradual increments in ambient temperature result in HSR activation exclusively in wild-type C. elegans head neurons. This is the first study to suggest that a thermostat-based mechanism can centrally and non-cell autonomously coordinate membrane fluidity in response to warm temperatures across tissues in multicellular animals.


This work will give rise to several publications:


• \"\"Bone Morphogenetic Protein acts downstream of neuronal HSF-1 to coordinate fat desaturation in the plasma membrane across tissues in C.elegans\"\"
Chauve L, Murdoch S, Masoudzadeh F, ; Hodge F, ; Lopez-Clavijo A, Okkenhaug H, West G, Segonds-Pichon A, Wingett S, Kienberger K, Kleigrewe H, Wakelam M, Casanueva, O
https://www.biorxiv.org/content/10.1101/2019.12.20.882514v2

• \"\"Neuronal XBP-1 Activates Intestinal Lysosomes to Improve Proteostasis in C. elegans.\"\" Özbey I, Krueger C, Casanueva MO, Taylor RC. Current Biology,.
doi: 10.1016/j.cub.2019.06.031.

• \"\"Worm-align and Worm_CP, two open-source pipelines for straightening and quantification of fluorescence image data obtained from Caenorhabditis elegans\"\"
Okkenhaug, H; Chauve, L; Masoudzadeh, F and Casanueva, O.

• \"\"Tyramine acts downstream of neuronal XBP-1s to coordinate inter-tissue UPRER activation and behavior in C. elegans\"\"
Özbey N, Imanikia I, Sheng M , Krueger C, Casanueva O, Taylor R. Manuscript in preparation.


4. Because we have found that a very important consequence is fat remodelling, we have focused our efforts in obtaining tools that can aid in the elucidation of mechanisms of metabolic remodelling.


• Witting, M; (…) Casanueva, O. (2018) “Modeling Meets Metabolomics—The WormJam Consensus Model as Basis for Metabolic Studies in the Model Organism Caenorhabditis elegans” Front. Mol. Biosci.| 5: 96
DOI=10.3389/fmolb.2018.00096


• Hastings J; Mains, A; Virk, B; Rodriguez, N; Murdoch, S. Pearce, J; Bergmann, S; Le Novère, N; Casanueva, O. “Multi-Omics and Genome-Scale Modelling reveal a Metabolic Shift During C. elegans Aging” (2019)
\"

Final results

As part as this ERC call, we have optimised technologies that allow us to detect rare single-worm transcripts and to measure inter-individual variability in its expression.
As future work for the remainder of the call, are looking into expanding computational tools such as network inference algorithms to further gain insights from single-worm data.
. Future work will include additional studies to uncover if inter-generational inheritance causes neuronal stress to vary across individuals.


We have also discovered a novel brain-gut axis that we think that fine-tunes ambient temperature with fat desaturation and fluidity.
As future work, we will continue to study at the mechanistic level how this mode of regulation works. We will continue to develop computational tools to study in silico, how neuronal stress alters fat metabolism. This includes the completion of the WormJam consensus model to gain insights into this problem.

Website & more info

More info: https://www.babraham.ac.uk/our-research/epigenetics/olivia-casanueva.