The Caenorhabditis elegans vab-10 spectraplakin isoforms protect the epidermis against internal and external forces

Morphogenesis of the Caenorhabditis elegans embryo is driven by actin microfilaments in the epidermis and by sarcomeres in body wall muscles. Both tissues are mechanically coupled, most likely through specialized attachment structures called fibrous organelles (FOs) that connect muscles to the cuticle across the epidermis. Here, we report the identification of new mutations in a gene known as vab-10, which lead to severe morphogenesis defects, and show that vab-10 corresponds to the C. elegans spectraplakin locus. Our analysis of vab-10 reveals novel insights into the role of this plakin subfamily. vab-10 generates isoforms related either to plectin (termed VAB-10A) or to microtubule actin cross-linking factor plakins (termed VAB-10B). Using specific antibodies and mutations, we show that VAB-10A and VAB-10B have distinct distributions and functions in the epidermis. Loss of VAB-10A impairs the integrity of FOs, leading to epidermal detachment from the cuticle and muscles, hence demonstrating that FOs are functionally and molecularly related to hemidesmosomes. We suggest that this isoform protects against forces external to the epidermis. In contrast, lack of VAB-10B leads to increased epidermal thickness during embryonic morphogenesis when epidermal cells change shape. We suggest that this isoform protects cells against tension that builds up within the epidermis

Adamtsl3 mediates DCC signaling to selectively promote GABAergic synapse function

The molecular code that controls synapse formation and maintenance in vivo has remained quite sparse. Here, we identify that the secreted protein Adamtsl3 functions as critical hippocampal synapse organizer acting through the transmembrane receptor DCC (deleted in colorectal cancer). Traditionally, DCC function has been associated with glutamatergic synaptogenesis and plasticity in response to Netrin-1 signaling. We demonstrate that early post-natal deletion of Adamtsl3 in neurons impairs DCC protein expression, causing reduced density of both glutamatergic and GABAergic synapses. Adult deletion of Adamtsl3 in either GABAergic or glutamatergic neurons does not interfere with DCC-Netrin-1 function at glutamatergic synapses but controls DCC signaling at GABAergic synapses. The Adamtsl3-DCC signaling unit is further essential for activity-dependent adaptations at GABAergic synapses, involving DCC phosphorylation and Src kinase activation. These findings might be particularly relevant for schizophrenia because genetic variants in Adamtsl3 and DCC have been independently linked with schizophrenia in patients

C. elegans : des neurones et des gènes

Que peut nous apprendre un ver sur le fonctionnement du cerveau humain? Les données acquises sur le système nerveux du nématode Caenorhabditis elegans démontrent l’existence d’une fascinante conservation de la biologie moléculaire et cellulaire du neurone au travers de plus de 550 millions d’années d’évolution séparant les nématodes des mammifères. C. elegans possède un système nerveux simple formé de 302 neurones et d’environ 7000 synapses. Des outils génétiques puissants permettent d’isoler de nouveaux gènes et d’attribuer à des gènes connus de nouvelles fonctions dans la mise en place et le fonctionnement du réseau neuronal du nématode. Nous montrerons par quelques exemples comment les découvertes faites chez C. elegans ont pu être rapidement transposées à la biologie du système nerveux des mammifères.The human brain contains 100 billion neurons and probably one thousand times more synapses. Such a system can be analyzed at different complexity levels, from cognitive functions to molecular structure of ion channels. However, it remains extremely difficult to establish links between these different levels. An alternative strategy relies on the use of much simpler animals that can be easily manipulated. In 1974, S. Brenner introduced the nematode Caenorhabditis elegans as a model system. This worm has a simple nervous system that only contains 302 neurons and about 7,000 synapses. Forward genetic screens are powerful tools to identify genes required for specific neuron functions and behaviors. Moreover, studies of mutant phenotypes can identify the function of a protein in the nervous system. The data that have been obtained in C. elegans demonstrate a fascinating conservation of the molecular and cellular biology of the neuron between worms and mammals through more than 550 million years of evolution

Agrégation synaptique des récepteurs du GABA et de l'acétylcholine aux jonctions neuromusculaires de Caenorhabditis elegans

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Synaptogenesis: unmasking molecular mechanisms using Caenorhabditis elegans.

The nematode Caenorhabditis elegans is a research model organism particularly suited to the mechanistic understanding of synapse genesis in the nervous system. Armed with powerful genetics, knowledge of complete connectomics, and modern genomics, studies using C. elegans have unveiled multiple key regulators in the formation of a functional synapse. Importantly, many signaling networks display remarkable conservation throughout animals, underscoring the contributions of C. elegans research to advance the understanding of our brain. In this chapter, we will review up-to-date information of the contribution of C. elegans to the understanding of chemical synapses, from structure to molecules and to synaptic remodeling

Study of the role of heat shock factor 1 in the development of Caenorhabditis elegans

Le facteur de transcription Heat Shock Factor 1 (HSF-1) régule l expression des chaperonnes moléculaires en conditions de stress. HSF-1 joue aussi un rôle important dans la longévité et lors du développement. Cependant, les fondements moléculaires relatifs au rôle d HSF-1 en l absence de stress, restent à élucider, à savoir, en particulier, si HSF-1 régule directement des gènes différents des chaperonnes moléculaires. C. elegans possède un seul gène hsf-1 ubiquitaire, qui est essentiel au développement. En effet, les mutants nuls hsf-1 arrêtent leur développement larvaire et meurent. Notre but est de déterminer les cibles transcriptionnelles d HSF-1 au cours du développement, en utilisant deux approches complémentaires; une approche chromatine Immunoprécipitation (ChIP) pour identifier les sites de liaisons à HSF-1, et une approche RNA-seq sous ARN interférence (ARNi) pour hsf-1, afin de déterminer les changements transcriptionnels associés. Nos résultats de RNA-seq suggèrent que l ARNi hsf-1 génère un fort effet secondaire sur l expression globale des gènes. Des catégories fonctionnelles similaires de gènes sont dérégulées sous ARNi hsf-1 au cours du développement, comportant des gènes impliqués dans la longévité, la réponse au stress, et le métabolisme des lipides. L analyse ChIP, que nous sommes en train de mener, nous permettra de déterminer les cibles primaires d HSF-1. A cette fin, nous avons généré une insertion simple-copie hsf-1, fusionné à la gfp, par la technique MosSCI. HSF-1 est nucléaire et forme des granules après heat shock. En l absence de stress, HSF-1 forme des granules lors des divisions embryonnaires, suggérant un rôle lors des divisions mitotiques.Heat shock factor 1 (HSF-1) is the major transcription factor that regulates expression of molecular chaperones upon proteotoxic conditions. In addition, HSF-1 plays an important role in the absence of stress, in development and lifespan. However, the molecular basis for the role of HSF-1 without stress remains to be elucidated, and especially whether HSF-1 directly regulates non-chaperone genes. In C. elegans, a single ubiquitous hsf-1 has been identified. HSF-1 is essential for nematode development, such that hsf-1 null mutants arrest at L2 larval stage and die. The goal of this study is to determine the transcriptional targets of HSF-1 during larval development. To achieve this, we are combining Chromatin Immunoprecipitation (ChIP) approach to identify HSF-1 binding sites, and RNA-seq analysis upon hsf-1 RNAi, to determine transcriptional changes associated with hsf-1 down-regulation. Our RNA-seq results suggest a strong secondary effect of hsf-1 RNAi on global gene expression. Similar functional gene categories are differentially regulated by hsf-1 RNAi throughout larval development, including lifespan, oxidative and heat stress response genes, and lipid metabolism genes. Our ongoing ChIP analysis will allow the determination of HSF-1 primary targets. To perform ChIP, we generated a single-copy insertion of hsf-1 tagged with gfp, carrying endogenous regulatory elements, via the MosSCI technique. HSF-1 exhibits a nuclear expression pattern with re-localization to intra-nuclear granule-like structures upon heat-shock. Strikingly, HSF-1 re-localizes constitutively to small intra-nuclear granules during embryonic divisions, suggesting a role during mitotic cell divisions.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Insulin/Insulin-Like Growth Factor Signaling Controls Non-Dauer Developmental Speed in the Nematode Caenorhabditis elegans

Identified as a major pathway controlling entry in the facultative dauer diapause stage, the DAF-2/Insulin receptor (InsR) signaling acts in multiple developmental and physiological regulation events in Caenorhabditis elegans. Here we identified a role of the insulin-like pathway in controlling developmental speed during the C. elegans second larval stage. This role relies on the canonical DAF-16/FOXO-dependent branch of the insulin-like signaling and is largely independent of dauer formation. Our studies provide further evidence for broad conservation of insulin/insulin-like growth factor (IGF) functions in developmental speed control

Image_1_Synapse Formation and Function Across Species: Ancient Roles for CCP, CUB, and TSP-1 Structural Domains.tif

The appearance of synapses was a crucial step in the creation of the variety of nervous systems that are found in the animal kingdom. With increased complexity of the organisms came a greater number of synaptic proteins. In this review we describe synaptic proteins that contain the structural domains CUB, CCP, or TSP-1. These domains are found in invertebrates and vertebrates, and CUB and CCP domains were initially described in proteins belonging to the complement system of innate immunity. Interestingly, they are found in synapses of the nematode C. elegans, which does not have a complement system, suggesting an ancient function. Comparison of the roles of CUB-, CCP-, and TSP-1 containing synaptic proteins in various species shows that in more complex nervous systems, these structural domains are combined with other domains and that there is partial conservation of their function. These three domains are thus basic building blocks of the synaptic architecture. Further studies of structural domains characteristic of synaptic proteins in invertebrates such as C. elegans and comparison of their role in mammals will help identify other conserved synaptic molecular building blocks. Furthermore, this type of functional comparison across species will also identify structural domains added during evolution in correlation with increased complexity, shedding light on mechanisms underlying cognition and brain diseases.Peer reviewe

Synapse Formation and Function Across Species: Ancient Roles for CCP, CUB, and TSP-1 Structural Domains

International audienceThe appearance of synapses was a crucial step in the creation of the variety of nervous systems that are found in the animal kingdom. With increased complexity of the organisms came a greater number of synaptic proteins. In this review we describe synaptic proteins that contain the structural domains CUB, CCP, or TSP-1. These domains are found in invertebrates and vertebrates, and CUB and CCP domains were initially described in proteins belonging to the complement system of innate immunity. Interestingly, they are found in synapses of the nematode C. elegans, which does not have a complement system, suggesting an ancient function. Comparison of the roles of CUB-, CCP-, and TSP-1 containing synaptic proteins in various species shows that in more complex nervous systems, these structural domains are combined with other domains and that there is partial conservation of their function. These three domains are thus basic building blocks of the synaptic architecture. Further studies of structural domains characteristic of synaptic proteins in invertebrates such as C. elegans and comparison of their role in mammals will help identify other conserved synaptic molecular building blocks. Furthermore, this type of functional comparison across species will also identify structural domains added during evolution in correlation with increased complexity, shedding light on mechanisms underlying cognition and brain diseases