Olivia Casanueva

Research Summary

Groundbreaking work in the nematode Caenorhabditis elegans has demonstrated that ageing is not simply a stochastic and progressive decay, but that it is genetically controlled by the longevity pathways. Strikingly, lifespan is highly variable even in genetically identical individuals reared under controlled environmental conditions.

We are interested in finding the mechanisms underlying transcriptional inter-individual variability in genes that modulate lifespan and determining to what extent it explains individual-to-individual differences in the rates of ageing. We are also interested in studying the influence of both stochastic and environmental variability during early life and its long-term effect on health. Dietary restriction (DR), reduced food intake without malnutrition, increases health and function during ageing and protects against ageing-related disease in most organisms. We are interested in understanding how early life nutrition (and DR) can set rates of ageing via epigenetic mechanisms.

Answering these questions requires the development of new technologies that make whole animals centre stage and will have a significant conceptual impact on ageing research and personalized medicine.  

Latest Publications

High-Throughput Quantitative RT-PCR in Single and Bulk C. elegans Samples Using Nanofluidic Technology.
Chauve L, Le Pen J, Hodge F, Todtenhaupt P, Biggins L, Miska EA, Andrews S, Casanueva O

This paper presents a high-throughput reverse transcription quantitative PCR (RT-qPCR) assay for Caenorhabditis elegans that is fast, robust, and highly sensitive. This protocol obtains precise measurements of gene expression from single worms or from bulk samples. The protocol presented here provides a novel adaptation of existing methods for complementary DNA (cDNA) preparation coupled to a nanofluidic RT-qPCR platform. The first part of this protocol, named 'Worm-to-CT', allows cDNA production directly from nematodes without the need for prior mRNA isolation. It increases experimental throughput by allowing the preparation of cDNA from 96 worms in 3.5 h. The second part of the protocol uses existing nanofluidic technology to run high-throughput RT-qPCR on the cDNA. This paper evaluates two different nanofluidic chips: the first runs 96 samples and 96 targets, resulting in 9,216 reactions in approximately 1.5 days of benchwork. The second chip type consists of six 12 x 12 arrays, resulting in 864 reactions. Here, the Worm-to-CT method is demonstrated by quantifying mRNA levels of genes encoding heat shock proteins from single worms and from bulk samples. Provided is an extensive list of primers designed to amplify processed RNA for the majority of coding genes within the C. elegans genome.

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Journal of visualized experiments : JoVE, 1, 159, 28 May 2020

PMID: 32538915

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, Okkenhaug L, Casanueva O

An issue often encountered when acquiring image data from fixed or anesthetized C. elegans is that worms cross and cluster with their neighbors. This problem is aggravated with increasing density of worms and creates challenges for imaging and quantification. We developed a FIJI-based workflow, Worm-align, that can be used to generate single- or multi-channel montages of user-selected, straightened and aligned worms from raw image data of C. elegans. Worm-align is a simple and user-friendly workflow that does not require prior training of either the user or the analysis algorithm. Montages generated with Worm-align can aid the visual inspection of worms, their classification and representation. In addition, the output of Worm-align can be used for subsequent quantification of fluorescence intensity in single worms, either in FIJI directly, or in other image analysis software platforms. We demonstrate this by importing the Worm-align output into Worm_CP, a pipeline that uses the open-source CellProfiler software. CellProfiler's flexibility enables the incorporation of additional modules for high-content screening. As a practical example, we have used the pipeline on two datasets: the first dataset are images of heat shock reporter worms that express green fluorescent protein (GFP) under the control of the promoter of a heat shock inducible gene hsp-70, and the second dataset are images obtained from fixed worms, stained for fat-stores with a fluorescent dye.

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Journal of visualized experiments : JoVE, 1, 159, 28 May 2020

PMID: 32538914

Autophagy compensates for defects in mitochondrial dynamics.
Haeussler S, Köhler F, Witting M, Premm MF, Rolland SG, Fischer C, Chauve L, Casanueva O, Conradt B

Compromising mitochondrial fusion or fission disrupts cellular homeostasis; however, the underlying mechanism(s) are not fully understood. The loss of C. elegans fzo-1MFN results in mitochondrial fragmentation, decreased mitochondrial membrane potential and the induction of the mitochondrial unfolded protein response (UPRmt). We performed a genome-wide RNAi screen for genes that when knocked-down suppress fzo-1MFN(lf)-induced UPRmt. Of the 299 genes identified, 143 encode negative regulators of autophagy, many of which have previously not been implicated in this cellular quality control mechanism. We present evidence that increased autophagic flux suppresses fzo-1MFN(lf)-induced UPRmt by increasing mitochondrial membrane potential rather than restoring mitochondrial morphology. Furthermore, we demonstrate that increased autophagic flux also suppresses UPRmt induction in response to a block in mitochondrial fission, but not in response to the loss of spg-7, which encodes a mitochondrial metalloprotease. Finally, we found that blocking mitochondrial fusion or fission leads to increased levels of certain types of triacylglycerols and that this is at least partially reverted by the induction of autophagy. We propose that the breakdown of these triacylglycerols through autophagy leads to elevated metabolic activity, thereby increasing mitochondrial membrane potential and restoring mitochondrial and cellular homeostasis.

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PLoS genetics, 16, 3, 19 Mar 2020

DOI: 10.1371/journal.pgen.1008638

PMID: 32191694