The Detection of Early Epigenetic Inheritance of Mitochondrial Stress in C. Elegans with a Microfluidic Phenotyping Platform

AbstractFluctuations and deterioration in environmental conditions potentially have a phenotypic impact that extends over generations. Transgenerational epigenetics is the defined term for such intergenerational transient inheritance without an alteration in the DNA sequence. The model organism Caenorhabditis elegans is exceptionally valuable to address transgenerational epigenetics due to its short lifespan, well-mapped genome and hermaphrodite behavior. While the majority of the transgenerational epigenetics on the nematodes focuses on generations-wide heritage, short-term and in-depth analysis of this phenomenon in a well-controlled manner has been lacking. Here, we present a novel microfluidic platform to observe mother-to-progeny heritable transmission in C. elegans at high imaging resolution, under significant automation, and enabling parallelized studies. After approximately 24 hours of culture of L4 larvae under various concentrations and application periods of doxycycline, we investigated if mitochondrial stress was transferred from the mother nematodes to the early progenies. Automated and custom phenotyping algorithms revealed that a minimum doxycycline concentration of 30 µg/mL and a drug exposure time of 15 hours applied to the mothers could induce mitochondrial stress in first embryo progenies indeed, while this inheritance was not clearly observed later in L1 progenies. We believe that our new device could find further usage in transgenerational epigenetic studies modeled on C. elegans.

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Alzheimer’s disease-relevant tau modifications selectively impact neurodegeneration and mitophagy in a novel C. elegans single-copy transgenic model

10.1101/2020.02.12.946004 ◽

2020 ◽

Cited By ~ 1

Author(s):

Sanjib Guha ◽

Sarah Fischer ◽

Gail VW Johnson ◽

Keith Nehrke

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Genetic Model ◽

Neurodegenerative Disorder ◽

Model Organism ◽

Single Copy ◽

Mitochondrial Stress ◽

C Elegans ◽

Touch Receptor Neurons ◽

New Perspective

ABSTRACTBackgroundA defining pathological hallmark of the progressive neurodegenerative disorder Alzheimer’s disease (AD) is the accumulation of misfolded tau with abnormal post-translational modifications (PTMs). These include phosphorylation at Threonine 231 (T231) and acetylation at Lysine 274 (K274) and at Lysine 281 (K281). Although tau is recognized to play a central role in pathogenesis of AD, the precise mechanisms by which these abnormal PTMs contribute to the neural toxicity of tau is unclear.MethodsHuman 0N4R tau (wild type) was expressed in touch receptor neurons of the genetic model organism C. elegans through single-copy gene insertion. Defined mutations were then introduced into the single-copy tau transgene through CRISPR-Cas9 genome editing. These mutations included T231E and T231A, to mimic phosphorylation and phospho-ablation of a commonly observed pathological epitope, respectively, and K274/281Q, to mimic disease-associated lysine acetylation. Stereotypical touch response assays were used to assess behavioral defects in the transgenic strains as a function of age, and genetically-encoded fluorescent biosensors were used to measure the morphological dynamics and turnover of touch neuron mitochondria.ResultsUnlike existing tau overexpression models, C. elegans single-copy expression of tau did not elicit overt pathological phenotypes at baseline. However, strains expressing disease associated PTM-mimetics (T231E and K274/281Q) exhibited reduced touch sensation and morphological abnormalities that increased with age. In addition, the PTM-mimetic mutants lacked the ability to engage mitophagy in response to mitochondrial stress.ConclusionsLimiting the expression of tau results in a genetic model where pathological modifications and age result in evolving phenotypes, which may more closely resemble the normal progression of AD. The finding that disease-associated PTMs suppress compensatory responses to mitochondrial stress provides a new perspective into the pathogenic mechanisms underlying AD.

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Tauopathy-associated tau modifications selectively impact neurodegeneration and mitophagy in a novel C. elegans single-copy transgenic model

Molecular Neurodegeneration ◽

10.1186/s13024-020-00410-7 ◽

2020 ◽

Vol 15 (1) ◽

Author(s):

Sanjib Guha ◽

Sarah Fischer ◽

Gail V. W. Johnson ◽

Keith Nehrke

Keyword(s):

Genetic Model ◽

Neurodegenerative Disorder ◽

Model Organism ◽

Single Copy ◽

Neuronal Morphology ◽

Mitochondrial Morphology ◽

Mitochondrial Stress ◽

C Elegans ◽

Touch Receptor Neurons ◽

New Perspective

Abstract Background A defining pathological hallmark of the progressive neurodegenerative disorder Alzheimer’s disease (AD) is the accumulation of misfolded tau with abnormal post-translational modifications (PTMs). These include phosphorylation at Threonine 231 (T231) and acetylation at Lysine 274 (K274) and at Lysine 281 (K281). Although tau is recognized to play a central role in pathogenesis of AD, the precise mechanisms by which these abnormal PTMs contribute to the neural toxicity of tau is unclear. Methods Human 0N4R tau (wild type) was expressed in touch receptor neurons of the genetic model organism C. elegans through single-copy gene insertion. Defined mutations were then introduced into the single-copy tau transgene through CRISPR-Cas9 genome editing. These mutations included T231E, to mimic phosphorylation of a commonly observed pathological epitope, and K274/281Q, to mimic disease-associated lysine acetylation – collectively referred as “PTM-mimetics” – as well as a T231A phosphoablation mutant. Stereotypical touch response assays were used to assess behavioral defects in the transgenic strains as a function of age. Genetically-encoded fluorescent biosensors were expressed in touch neurons and used to measure neuronal morphology, mitochondrial morphology, mitophagy, and macro autophagy. Results Unlike existing tau overexpression models, C. elegans single-copy expression of tau did not elicit overt pathological phenotypes at baseline. However, strains expressing disease associated PTM-mimetics (T231E and K274/281Q) exhibited reduced touch sensation and neuronal morphological abnormalities that increased with age. In addition, the PTM-mimetic mutants lacked the ability to engage neuronal mitophagy in response to mitochondrial stress. Conclusions Limiting the expression of tau results in a genetic model where modifications that mimic pathologic tauopathy-associated PTMs contribute to cryptic, stress-inducible phenotypes that evolve with age. These findings and their relationship to mitochondrial stress provides a new perspective into the pathogenic mechanisms underlying AD.

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High-Content C. elegans Screen Identifies Natural Compounds Impacting Mitochondria-Lipid Homeostasis and Promoting Healthspan

Cells ◽

10.3390/cells11010100 ◽

2021 ◽

Vol 11 (1) ◽

pp. 100

Author(s):

Silvia Maglioni ◽

Nayna Arsalan ◽

Anna Hamacher ◽

Shiwa Afshar ◽

Alfonso Schiavi ◽

...

Keyword(s):

Stress Response ◽

Lipid Content ◽

Model Organism ◽

Natural Compounds ◽

Extrinsic Factors ◽

Mitochondrial Stress ◽

C Elegans ◽

Stress Response Genes ◽

Age Related ◽

Kahalalide F

The aging process is concurrently shaped by genetic and extrinsic factors. In this work, we screened a small library of natural compounds, many of marine origin, to identify novel possible anti-aging interventions in Caenorhabditis elegans, a powerful model organism for aging studies. To this aim, we exploited a high-content microscopy platform to search for interventions able to induce phenotypes associated with mild mitochondrial stress, which is known to promote animal’s health- and lifespan. Worms were initially exposed to three different concentrations of the drugs in liquid culture, in search of those affecting animal size and expression of mitochondrial stress response genes. This was followed by a validation step with nine compounds on solid media to refine compounds concentration, which led to the identification of four compounds (namely isobavachalcone, manzamine A, kahalalide F and lutein) consistently affecting development, fertility, size and lipid content of the nematodes. Treatment of Drosophila cells with the four hits confirmed their effects on mitochondria activity and lipid content. Out of these four, two were specifically chosen for analysis of age-related parameters, kahalalide F and lutein, which conferred increased resistance to heat and oxidative stress and extended animals’ healthspan. We also found that, out of different mitochondrial stress response genes, only the C. elegans ortholog of the synaptic regulatory proteins neuroligins, nlg-1, was consistently induced by the two compounds and mediated lutein healthspan effects.

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Odor Sensitivity as a Biomarker of Aging

Innovation in Aging ◽

10.1093/geroni/igaa057.400 ◽

2020 ◽

Vol 4 (Supplement_1) ◽

pp. 121-122

Author(s):

Marjana Sarker ◽

Scott Leiser

Keyword(s):

Olfactory System ◽

Healthy Adult ◽

Model Organism ◽

Olfactory Neurons ◽

Adult Lifespan ◽

C Elegans ◽

Short Lifespan ◽

Age Related ◽

Odor Sensitivity ◽

Biomarker Of Aging

Abstract Recent studies support the deterioration of the sense of smell as an important biomarker for cognitive impairment diseases, including Alzheimer’s disease. The model organism C. elegans has a well-studied olfactory system, which provides an ideal platform to measure loss of smell with aging. The goal of our project is to use the short lifespan and olfactory changes observed in nematodes to identify mechanisms to slow aging and treat age-related diseases. Our approach is to utilize worms at various times of their healthy adult lifespan and to test for their sensitivity to known attractants such as benzaldehyde. These odorants are largely detected by the main AWC olfactory neurons. It is well documented that the responsiveness of AWC decreases with age. Our paradigm is to briefly fast worms to increase motivation before testing their ability to discriminate odors. Our results show that younger worms actively move toward the attractant and show preference for specific attractants. However, older worms frequently do not respond to attractive odors and remain near the point of origin, regardless of motility. These results indicate a decreased odor response with age. Our current work focuses on identifying genes and compounds that positively affect this odor response in older animals. The resulting data can then be tested for their efficacy to improve other aspects of healthspan and potentially longevity.

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Multigenerational Regulation of the Caenorhabditis elegans Chromatin Landscape by Germline Small RNAs

Annual Review of Genetics ◽

10.1146/annurev-genet-112618-043505 ◽

2019 ◽

Vol 53 (1) ◽

pp. 289-311 ◽

Cited By ~ 10

Author(s):

Natasha E. Weiser ◽

John K. Kim

Keyword(s):

Gene Expression ◽

Caenorhabditis Elegans ◽

Small Rnas ◽

Model Organism ◽

Epigenetic Inheritance ◽

Small Interfering Rnas ◽

Transgenerational Epigenetic Inheritance ◽

C Elegans ◽

Small Noncoding Rnas ◽

Rna Pathways

In animals, small noncoding RNAs that are expressed in the germline and transmitted to progeny control gene expression to promote fertility. Germline-expressed small RNAs, including endogenous small interfering RNAs (endo-siRNAs) and Piwi-interacting RNAs (piRNAs), drive the repression of deleterious transcripts such as transposons, repetitive elements, and pseudogenes. Recent studies have highlighted an important role for small RNAs in transgenerational epigenetic inheritance via regulation of heritable chromatin marks; therefore, small RNAs are thought to convey an epigenetic memory of genomic self and nonself elements. Small RNA pathways are highly conserved in metazoans and have been best described for the model organism Caenorhabditis elegans. In this review, we describe the biogenesis, regulation, and function of C. elegans endo-siRNAs and piRNAs, along with recent insights into how these distinct pathways are integrated to collectively regulate germline gene expression, transgenerational epigenetic inheritance, and ultimately, animal fertility.

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Loss of Muscleblind Splicing Factor Shortens C. elegans Lifespan by Reducing the Activity of p38 MAPK/PMK-1 and Transcription Factors ATF-7 and Nrf/SKN-1

Genetics ◽

10.1093/genetics/iyab114 ◽

2021 ◽

Author(s):

Olli Matilainen ◽

Ana R S Ribeiro ◽

Jens Verbeeren ◽

Murat Cetinbas ◽

Heini Sood ◽

...

Keyword(s):

Transcription Factors ◽

P38 Mapk ◽

Rna Binding ◽

Model Organism ◽

Accelerated Aging ◽

Splicing Factor ◽

Dependent Manner ◽

Mitochondrial Stress ◽

C Elegans ◽

Splicing Regulators

Abstract Muscleblind-like splicing regulators (MBNLs) are RNA-binding factors that have an important role in developmental processes. Dysfunction of these factors is a key contributor of different neuromuscular degenerative disorders, including Myotonic Dystrophy type 1 (DM1). Since DM1 is a multisystemic disease characterized by symptoms resembling accelerated aging, we asked which cellular processes do MBNLs regulate that make them necessary for normal lifespan. By utilizing the model organism Caenorhabditis elegans, we found that loss of MBL-1 (the sole ortholog of mammalian MBNLs), which is known to be required for normal lifespan, shortens lifespan by decreasing the activity of p38 MAPK/PMK-1 as well as the function of transcription factors ATF-7 and SKN-1. Furthermore, we show that mitochondrial stress caused by knockdown of mitochondrial electron transport chain components promotes the longevity of mbl-1 mutants in a partially PMK-1-dependent manner. Together, the data establish a mechanism of how DM1-associated loss of muscleblind affects lifespan. Furthermore, this study suggests that mitochondrial stress could alleviate symptoms caused by the dysfunction of muscleblind splicing factor, creating a potential approach to investigate for therapy.

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Loss of Muscleblind Splicing Factor Shortens C. elegans Lifespan by Reducing the Activity of p38 MAPK/PMK-1 and Transcription Factors ATF-7 and Nrf/SKN-1

10.1101/2021.02.22.432374 ◽

2021 ◽

Author(s):

Olli Matilainen ◽

Ana R. S. Ribeiro ◽

Jens Verbeeren ◽

Murat Cetinbas ◽

Ruslan I. Sadreyev ◽

...

Keyword(s):

Transcription Factors ◽

P38 Mapk ◽

Model Organism ◽

Accelerated Aging ◽

Splicing Factor ◽

Dependent Manner ◽

Mitochondrial Stress ◽

C Elegans ◽

Splicing Regulators ◽

Multisystemic Disease

AbstractMuscleblind-like splicing regulators (MBNLs) are alternative splicing factors that have an important role in developmental processes. Dysfunction of these factors is a key contributor of different neuromuscular degenerative disorders, including Myotonic Dystrophy type 1 (DM1). Since DM1 is a multisystemic disease characterized by symptoms resembling accelerated aging, we asked whether MBNLs regulate cellular processes required to maintain normal lifespan. By utilizing the model organism Caenorhabditis elegans, we found that loss of MBL-1 (the sole ortholog of mammalian MBNLs), which is known to be required for normal lifespan, shortens lifespan by decreasing the activity of p38 MAPK/PMK-1 as well as the function of transcription factors ATF-7 and SKN-1. Furthermore, we show that mitochondrial stress caused by knockdown of mitochondrial electron transport chain components promotes the longevity of mbl-1 mutants in a partially PMK-1-dependent manner. Together, the data establish a mechanism of how DM1-associated loss of muscleblind affects lifespan. Furthermore, this study suggests that mitochondrial stress could alleviate symptoms caused by the dysfunction of muscleblind splicing factor, creating a potential approach to investigate for therapy.Reviewer token for the RNA-seq data (GEO: GSE146801): wvataksittaffcj

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How do histone modifications contribute to transgenerational epigenetic inheritance in C. elegans?

Biochemical Society Transactions ◽

10.1042/bst20190944 ◽

2020 ◽

Vol 48 (3) ◽

pp. 1019-1034 ◽

Cited By ~ 1

Author(s):

Rachel M. Woodhouse ◽

Alyson Ashe

Keyword(s):

Histone Modifications ◽

Molecular Mechanisms ◽

Epigenetic Inheritance ◽

Nematode Caenorhabditis Elegans ◽

Histone Methyltransferases ◽

Transgenerational Epigenetic Inheritance ◽

C Elegans ◽

Recent Developments ◽

Gene Regulatory

Gene regulatory information can be inherited between generations in a phenomenon termed transgenerational epigenetic inheritance (TEI). While examples of TEI in many animals accumulate, the nematode Caenorhabditis elegans has proven particularly useful in investigating the underlying molecular mechanisms of this phenomenon. In C. elegans and other animals, the modification of histone proteins has emerged as a potential carrier and effector of transgenerational epigenetic information. In this review, we explore the contribution of histone modifications to TEI in C. elegans. We describe the role of repressive histone marks, histone methyltransferases, and associated chromatin factors in heritable gene silencing, and discuss recent developments and unanswered questions in how these factors integrate with other known TEI mechanisms. We also review the transgenerational effects of the manipulation of histone modifications on germline health and longevity.

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Health and longevity studies in C. elegans: the “healthy worm database” reveals strengths, weaknesses and gaps of test compound-based studies

Biogerontology ◽

10.1007/s10522-021-09913-2 ◽

2021 ◽

Vol 22 (2) ◽

pp. 215-236

Author(s):

Nadine Saul ◽

Steffen Möller ◽

Francesca Cirulli ◽

Alessandra Berry ◽

Walter Luyten ◽

...

Keyword(s):

Healthy Aging ◽

Model Organism ◽

Research Field ◽

Aging Research ◽

Genetic Manipulations ◽

C Elegans ◽

Starting Point ◽

Health Related ◽

Phenotype Measurement ◽

Or Gene

AbstractSeveral biogerontology databases exist that focus on genetic or gene expression data linked to health as well as survival, subsequent to compound treatments or genetic manipulations in animal models. However, none of these has yet collected experimental results of compound-related health changes. Since quality of life is often regarded as more valuable than length of life, we aim to fill this gap with the “Healthy Worm Database” (http://healthy-worm-database.eu). Literature describing health-related compound studies in the aging model Caenorhabditis elegans was screened, and data for 440 compounds collected. The database considers 189 publications describing 89 different phenotypes measured in 2995 different conditions. Besides enabling a targeted search for promising compounds for further investigations, this database also offers insights into the research field of studies on healthy aging based on a frequently used model organism. Some weaknesses of C. elegans-based aging studies, like underrepresented phenotypes, especially concerning cognitive functions, as well as the convenience-based use of young worms as the starting point for compound treatment or phenotype measurement are discussed. In conclusion, the database provides an anchor for the search for compounds affecting health, with a link to public databases, and it further highlights some potential shortcomings in current aging research.

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Benefits of Using the Invertebrate Model Organism C. Elegans in an Inquiry-Based Laboratory Activity

Teaching of Psychology ◽

10.1177/00986283211029649 ◽

2021 ◽

pp. 009862832110296

Author(s):

Angy J. Kallarackal

Keyword(s):

American Psychological Association ◽

Model Organism ◽

Learning Goals ◽

Research Skills ◽

Final Exam ◽

Laboratory Activity ◽

Writing Ability ◽

C Elegans ◽

Invertebrate Model ◽

Laboratory Experiences

Background: The goals of laboratory experiences include developing knowledge base, research skills, and scientific communication abilities. Objective: The aim was to assess an inquiry-based laboratory activity using the model organism Caenorhabditis elegans in relation to learning goals. Method: Students in a Biopsychology laboratory course worked in groups to test the effect of various drugs (e.g., nicotine, ethanol, fluoxetine, and melatonin) on C. elegans behavior. The activity included literature review, experimental design, and a final lab report. A cumulative final exam included a synaptic communication question related to the content of the activity. Results: Students showed better retention of laboratory-related content compared to other topics from the course, as demonstrated through performance on the final exam and were able to replicate previous research demonstrating effects of drug on locomotion. However, students did not improve writing ability compared to performance on a previous American Psychological Association style lab report. Conclusion: This study demonstrates that using a student-designed, multi-week laboratory assignment in an undergraduate Biopsychology course supports the growth of psychology knowledge and the development of research skills. Teaching Implications: Instructors should consider using the described laboratory activity for biopsychology or behavioral neuroscience classes or consider similarly designed laboratory formats for other courses in Psychology.

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