Slo2, a large conductance potassium channel in the nervous system is important for regulating neuronal function and excitability. Mutations in the gene that encodes the Slo2 channel are associated with neurological disorders, including epilepsy and intellectual disabilities in humans. However, much remains unknown about the genes and proteins that regulate Slo2 channel activity in the physiological system. This study investigates regulation of SLO-2, a homologue of mammalian Slo2 in C. elegans, by thoc-7 in an RNA editing-dependent pathway. Prior research has shown that adr-1, the gene important for RNA editing, promotes SLO-2 function by RNA editing of scyl-1 that encodes a regulator of SLO-2. To gain a better understanding of the regulation of SLO-2, this study employed a forward genetic approach to screen for mutants with a specific phenotype. Through SNP mapping and whole genome sequencing, we identified the gene thoc-7, which is predicted to be involved in mRNA export from nucleus, from the isolated mutants. The identification was further confirmed by CRISPR/Cas9-mediated gene knock-out, which showed a similar phenotype to the mutant strain. Results of electrophysiological recordings suggest that thoc-7 likely contributes to SLO-2 function in a common pathway with scyl-1. A reporter gene revealed strong expression of thoc-7 in most of the cells of C. elegans, particularly muscular and digestive system. Translational fusion with GFP showed the primary localization of the THOC-7 protein in cytoplasm, with some weak expression in the nucleus. RT-qPCR analysis suggests that thoc-7 regulates scyl-1 by through a post-transcriptional mechanism, possibly involving the transport of mRNA from cytoplasm to nucleus. This study highlights thoc-7 as a potential key regulator recruited by adr-1 to control SLO-2 via scyl-1 expression.

Actuellement, plus de soixante-dix dystrophies musculaires différentes ont été caractérisées cliniquement. La pathogenèse des différents types de dystrophies musculaire implique de nombreuses voies biologiques et s'accompagne d'une grande variabilité de signes cliniques, mais toutes ces dystrophies ont une caractéristique commune : la perte progressive des fibres musculaires. Pour les formes plus communes de ces dystrophies musculaires, les stratégies thérapeutiques visent principalement à restaurer la fonction du gène altéré. Bien que ces stratégies soient encourageantes pour un grand nombre de patients, elles ne peuvent être retenues comme traitement universel pour l'ensemble des dystrophies musculaires. L'identification de voies biologiques et de défauts secondaires communs à des dystrophies musculaires représente un intérêt majeur pour le développement de traitements palliatifs généralistes applicables à un large éventail de dystrophies musculaires. Pendant mes travaux de doctorat, j'ai initié une étude comparative approfondie sur dix-sept mutants différents chez le nématode Caenorhabditis elegans présentant une dégénérescence musculaire progressive, dont sept sont des modèles de dystrophies musculaires chez le nématode. La recherche de voies biologiques et de défauts secondaires communs, nous a permis d'établir différentes classes de dégénérescence musculaire chez le nématode et de révéler l'existence d'au moins deux mécanismes subcellulaires différents. De plus, nos résultats démontrent que des perturbations de la voie autophagique semblent systématiquement associées à la dégénérescence musculaire. Enfin, ce travail aboutit sur l'établissement d'un modèle proposant une chronologie des évènements sub-cellulaires menant à la dégénérescence progressive dystrophine-dépendante / Currently, more than sevently different muscular dystrophies have been clinically characterized. The pathogenesis of these different types of muscular dystrophies involves numerous cellular pathways and leads to a large variability of the clinical features. However, all the muscular dystrophies share a common feature: the progressive muscle cell loss. For the most common forms of muscular dystrophies, therapeutic strategies consist in restoring the function of the affected gene. Even if these strategies are encouraging for a lot of patients, they cannot be used as a universal treatment for all the muscular dystrophies. The identification if common pathways or common secondary defects to different muscular dystrophies is of great interest for the discovery of new palliative treatment, able to decrease the pathology of a large panel of muscular dystrophies. I have initiated a comparative analysis of seventeen C. elegans mutants presenting with muscle degeneration. Seven these mutants are considered as models for muscular dystrophies. Thanks to these comparative analysis, we were able to define different classes of muscle degeneration in C. elegans and to reveal the existence of at leats two different pathways. Moreover, our results show that perturbations in the autophagic pathway are systematically associated with muscle degeneration. This study leads to the establishment of a putative chronology of events occurring before the muscle cell loss, during the dystrophin-dependent degeneration process

Submitted by Marcos Anselmo (marcos.anselmo@unipampa.edu.br) on 2016-04-18T17:23:20Z No. of bitstreams: 1 Suzi Wollenhaupt.pdf: 1934742 bytes, checksum: 05b51e77aeefc91c2211fee9a7cd6131 (MD5) / Made available in DSpace on 2016-04-18T17:23:20Z (GMT). No. of bitstreams: 1 Suzi Wollenhaupt.pdf: 1934742 bytes, checksum: 05b51e77aeefc91c2211fee9a7cd6131 (MD5) Previous issue date: 2013-05-10 / Compostos orgânicos de selênio (Se) e telúrio (Te) apresentam propriedades antioxidantes em muitos modelos de estresse oxidativo. No entanto, devido à complexidade dos modelos de mamíferos, tem sido difícil de determinar as vias moleculares e proteínas específicas que são moduladas em resposta aos tratamentos com esses compostos. Neste contexto, o presente trabalho investigou os efeitos e possíveis mecanismos de ação de uma nova classe de compostos orgânicos de Se e Te chamados Xilofuranosídeos, utilizando como modelo experimental alternativo o nematóide Caenorhabditis elegans (C. elegans). Tal modelo permite fácil manipulação genética, marcação de diversas proteínas com proteína verde fluorescente e análise de toxicidade in vivo e ao vivo. Neste estudo, desafiamos os nematóides ao manganês (Mn), um agente pró-oxidante conhecido, uma vez que evidências apontam que o estresse oxidativo é consequência da sua toxicidade. Utilizando este agente pró-oxidante, investigamos a eficácia do Se e Te-xylofuranosídeos em reverter e/ou proteger os vermes da toxicidade induzida por Mn. Adicionalmente, investigamos um suposto mecanismo de ação. Primeiramente encontramos a dose letal 50% dos compostos, as quais foram de 0,73mM e 0,8mM para os compostos contendo Se e Te, respectivamente. Em concentrações subletais, encontramos que ambos Se e Te-xylofuranosídeo reverteram à mortalidade induzida por Mn, diminuíram a produção de espécies reativas de oxigênio (ERO) e aumentaram a expressão da superóxido dismutase (SOD-3::GFP), indicando que o aumento na sobrevivência está associado com a diminuição do estresse oxidativo. Além disso, observamos que os Se e Te-xylofuranosídeos induzem a translocação nuclear do fator de transcrição DAF-16/FOXO, que no viii verme é conhecido por regular a resposta ao estresse, envelhecimento e metabolismo e tem também como gene alvo a sod-3, corroborando com o aumento na expressão da proteína codificada por este gene. Esses achados sugerem que os Se e Te-xylofuranosídeos atenuam a geração de espécies reativas induzidas por Mn através da regulação da via de sinalização DAF-16/FOXO. / Organoselenium and organotellurium compounds have been reported as antioxidant in several models of oxidative stress. Nevertheless, because of the complexity of mammalian models, it has been difficult to determine the molecular pathways and specific proteins that are modulated in response to treatments with these compounds. In this context, the present study investigated the effects and action mechanisms of a novel class of organic compounds of selenium (Se) and tellurium (Te) called Xylofuranosides, utilizing as an alternative experimental model the nematode Caenorhabditis elegans (C. elegans), that affords easy genetic manipulations, green fluorescent protein tagging and in vivo live analysis of toxicity. In this study, we challenged worms to manganese (Mn), a known pro oxidizing agent, as there is abundant evidence pointing out to oxidative stress in mediating its toxicity. We investigated the efficacy of Se- and Te- xylofuranosides in reversing and/or protecting the worms from Mn-induced toxicity. In addition, we investigated their putative mechanism of action. First, we found the lethal dose 50% (LD50) for the compounds, which were 0.73mM and 0.8mM for Se and Te compound, respectively. This was followed by studies on the ability of the xylofuranosides to afford protection against Mn-induced toxicity. Both Se and Te-xylofuranosides reversed the Mn-lethality, decreased reactive oxygen species (ROS) production and increased the expression of superoxide dismutase (SOD-3), indicating that the increased survival was associated with decreased oxidative stress. Furthermore, we observed that the xylofuranosides induced nuclear translocation of the transcriptional factor DAF-16/FOXO, which in the worm is known to regulate stress responsiveness, aging, metabolism and the expression of SOD-3, as verified in this study. These findings x suggest that xylofuranosides attenuate Mn-induced ROS generation by regulating the DAF-16/FOXO signaling pathway.

No description available.

Les nanoparticules de dioxyde de titane sont aujourd’hui utilisées dans denombreux domaines. Elles entrent notamment dans la constitution de produits d’usagecourant comme les peintures ou certains produits cosmétiques (crèmes solaires). La taillenanométrique leur confère une réactivité accrue ce qui soulève des inquiétudes sur leurpossible toxicité. Des nanoparticules de morphologies contrôlées ont été synthétisées etcaractérisées. Elles ont ensuite été introduites dans le milieu de cellules humaines enculture afin d’observer les interactions in vitro et identifier les raisons de cette toxicité.L’étude a ensuite été étendue à l’in vivo avec un organisme pluricellulaire : le nématodeCaenorhabditis elegans (C. elegans).Les recherches ont été focalisées sur la détection, la localisation et la quantification desnanoparticules à l’échelle de la cellule unique puis dans les nématodes. Les différentesnanoparticules synthétisées ont permis d’identifier les propriétés physico-chimiquessusceptibles d’influer sur la toxicité. Les techniques d’analyse par faisceau d’ions ont permisde visualiser voire même de quantifier ces nano-objets à l’échelle de la cellule unique. / Titanium dioxide nanoparticles are nowadays used in numerous domains. Theyenter in particular in the constitution of every day’s products such as paints or cosmetics(sun screen). The nanometer scale gives them a high reactivity which raises worries abouttheir possible toxicity. Nanoparticles with controlled morphologies were synthesized andcharacterized. They were then introduced in the medium of human cells in cultivation inorder to observe in vitro interactions and identify the reasons of this toxicity. The study wasthen extended to in vivo with a multi-cellular specimen: the nematode Caenorhabditiselegans (C. elegans).Researches have been focalized on detection, tracking and quantification of nanoparticles atthe scale of single-cells and then in nematodes. The different kinds of synthesizednanoparticles allowed identifying the physico-chemical properties involved in their toxicity.Ion beam analyses were conducted in order to visualize and in some case quantify thisnano-objects at the single cell-scale.

Comprendre comment les facteurs génétiques et environnementaux interagissent au cours du développement est une question fondamentale en biologie. Je me suis intéressée à cette question en utilisant le réseau de développement de la vulve du nématode C. elegans comme système modèle. L’objectif de mon projet était une étude quantitative de la modulation par l’environnement des voies de signalisation impliquées dans ce processus telles que, Ras, Delta-Notch et Wnt. J’ai tout d’abord analysé comment un facteur environnemental spécifique (la carence nutritionnelle) modifie les activités et les interactions entre les voies de signalisation sous-jacentes au développement vulvaire chez C. elegans. J’ai ainsi mis en évidence que l’augmentation de l’induction vulvaire par la carence passe par une augmentation de l’activité de la voie Ras et est indépendante de la voie Wnt. Cet effet de l’environnement est assuré par la détection de la diminution de l’apport en nutriments, probablement par l’action de la voie TOR, et affecte l’induction vulvaire en parallèle ou en amont du récepteur à l’EGF. J’ai ensuite examiné la sensibilité environnementale du système de développement de la vulve de Caenorhabditis dans une perspective évolutive et ce, grâce à l'analyse comparative de différents isolats. J’ai pu observer que l’exposition à des températures extrêmes induit des variants et des défauts de manière fortement dépendante de la souche et de l’espèce. L’occurrence de certains défauts développementaux induits par la température révèlent en outre que certaines cellules précurseurs de la vulve et les voies de signalisation associées présentent une sensibilité environnementale différente. / How genetic and environmental factors interact during development is a key question in current biology, yet little is known about how molecular and cellular processes integrate environmental information. In my PhD research I aimed to address this problem using the network of C. elegans vulval signalling pathways as a model system. The principal objective of my project was to quantitatively examine how involved major signalling pathways, EGF-Ras-MAPK, Wnt and Delta-Notch, are modulated by specific environmental signals. First, I analysed how a specific environmental factor (starvation) alters activities and interplay of signalling pathways underlying C. elegans vulval cell fate patterning. I found that starvation consistently increased vulval induction through upregulation of the EGF-Ras-MAPK pathway activity independent of the Wnt pathway. This environmental effect is mediated by internal sensing of nutrient deprivation, likely acting through the TOR pathway, and affects vulval induction at the level or upstream of the EGF receptor. Second, I examined the environmental sensitivity of the Caenorhabditis vulval developmental system from an evolutionary perspective through comparative analysis of different C. elegans and C. briggsae isolates. I found that extreme temperature induced diverse developmental variants and defects, which were strongly genotype- and species-dependent. The occurrence of certain developmental defects induced by temperature extremes further revealed that vulval precursor cells and associated fates differ in temperature sensitivity, and this cell-specific sensitivity shows evolutionary variation.

Nous avons adapté avec succès un protocole de transformation médiée par PEG pour D. coniospora. En collaboration avec le ccdB et la méthode de construction de plasmide à base de Gibson, nous avons établi un système pour manipuler génétiquement ce champignon qui sert comme un outil important pour l'hôte-pathogène étude d'interaction. Nous avons identifié le mode de vie pathogène spécifique de D. coniospora sur la base de sa séquence génomique. analyse génomique comparative a révélé une liste des effecteurs fongiques potentiels qui se livrent à l'immunité de l'hôte, par exemple SAPA (G3895). Nous avons également construit une souche rapporteuse pour SAPA et identifié sa cible hôte SPP-5, un peptide antimicrobien. Notre étude se concentrant particulièrement sur l'agent pathogène fournit un aperçu de l'interaction hôte-pathogène entre C. elegans et D. coniospora.En dépit de la génération réussie de 5 D. coniospora souches transgéniques. Néanmoins, les problèmes qui subsistent, tels que le transfert multiple lors de protoplastes préparation et la croissance lente de D. coniospora après transformation doivent encore être résolus. L'une des solutions est de remplacer le moyen général avec un milieu qui ressemble à l'environnement hôte. / We have successfully adapted a PEG-mediated transformation protocol for D. coniospora. Together with the ccdB and Gibson based plasmid construction method, we established a system to genetically manipulate this fungus which serves as an important tool for host-pathogen interaction study. We identified the specific pathogenic lifestyle of D. coniospora based on its genomic sequence. Comparative genomic analysis revealed a list of potential fungal effectors which engage with the host immunity, for instance SapA (G3895). We further constructed a reporter strain for SapA and identified its host target SPP-5, an antimicrobial peptide. Our study focusing particularly on the pathogen provides an insight for the host-pathogen interaction between C. elegans and D. coniospora. Despite the successful generation of 5 D. coniospora transgenic strains. Nevertheless, the remaining problems such as multiple transferring during protoplasts preparation and slow growth of D. coniospora after transformation still need to be resolved. One of the solutions is to substitute the general medium with a medium resembling the host environment.We show that D. coniospora SapA protein interacts with worm immune effector, SPP-5 in vitro indicating its potential role to suppress the host immunity. Due to the fact that SapA is also highly expressed at the late stage of infection, we cannot rule out the other possible functions of this protein. We could employ Mass spectrometry technique to identify other host proteins which interact with SapA in vivo.

L’augmentation transitoire de la concentration calcique intracellulaire constitue l’élément déclencheur de nombreux processus physiologiques tels que la fertilisation de l’ovocyte, la contraction ou la mort cellulaire. L’influx de calcium à la suite de l’activation des récepteurs de l’acétylcholine (RACh) dans les muscles ou les neurones est un événement bref et localisé. Le recrutement, direct ou indirect, des canaux calciques voltage-dépendants permet de convertir cette stimulation aigue en un événement prolongé dans l’espace et le temps, menant à la contraction musculaire, à l’exocytose des neurotransmetteurs ou à la régulation de l’expression des gènes. Les RACh et les canaux de type L étant conservés au cours de l’évolution, nous utilisons la cellule musculaire du nématode Caenorhabditis elegans comme modèle d’étude afin de mieux caractériser la biologie et les mécanismes de régulation de ces protéines. Au cours de ma thèse, j’ai travaillé sur deux situations indépendantes de suractivation de l’homéostasie calcique impliquant ces acteurs, i) l’hyperactivation des canaux calciques voltage-dépendants par des mutations gain-de-fonction, ii) la suractivation pharmacologique des RACh à l’aide d’un agoniste cholinergique, le lévamisole. La première étude a consisté en la caractérisation de trois mutations gain-de-fonction dans le gène codant la sous-unité a1 du canal calcique de type L. Ce travail s’inscrivait dans un projet visant à isoler des mutants supprimant les défauts d’excitabilité engendrés par l’hyperactivité des canaux de type L, afin d’identifier de nouveaux partenaires fonctionnels de ces canaux. Ce projet a été interrompu par la mise en place de la deuxième étude, dans laquelle j’ai utilisé l’exposition au lévamisole pour explorer la réponse cellulaire face à une suractivation cholinergique. J’ai montré que la signalisation cholinergique était contrôlée par un inhibiteur associé aux récepteurs, et que les RACh subissaient des modifications quantitatives à court ou long terme. Enfin, j'ai exploité le phénotype de résistance partielle au lévamisole pour réaliser un crible génétique à grande échelle visant à identifier de nouveaux régulateurs des récepteurs / Calcium transients trigger various physiological processes, including oocyte fertilization, contraction or cell death. In neurons or muscles, calcium influx following acetylcholine receptor (AChR) opening is a brief and confined event. By recruiting, directly or not, voltage-dependent calcium channels, this calcium entry is amplified through space and time and leads to muscle contraction, neurotransmitter exocytosis or gene regulation.As AChRs and L-type voltage-gated calcium channels are evolutionarily conserved, we use Caenorhabditis elegans striated muscle cells as a model to characterize the biology and regulation mechanisms of these proteins. During my PhD I worked on two independent situations involving overactivation of calcium homeostasis, i) hyperactivation of L-type calcium channels by gain-of-function mutations within the main subunit, ii) pharmacological overactivation of AChRs using the cholinergic agonist levamisole. The functional characterization of three gain-of-function mutations was the first step of a project aiming to identify new molecular partners of L-type channels, by isolating mutants suppressing excitability troubles introduced by these gain-of-function mutations. This work was interrupted when I started the second study: I used levamisole exposure as an experimental paradigm to investigate how muscle cells are coping with cholinergic overstimulation. I showed that cholinergic signaling is regulated by an inhibitor associated with the receptors, and that AChRs undergo quantitative changes at short or long term. Finally I took advantage of partial levamisole resistance phenotype to undertake a genetic screen in order to identify new regulators of AChRs

La progression de l’espérance de vie observée au cours du XXième siècle a été accompagnée par une augmentation massive de l’incidence des maladies liées à l’âge et en particulier des maladies neurodégénératives. Malheureusement, les thérapeutiques actuelles ciblant principalement les anomalies d’agrégation protéique caractérisant ces maladies, tel que la maladie d’Alzheimer, ont échoué au niveau des essais cliniques. De récentes études épidémiologiques ont suggéré un lien entre la dysfonction métabolique et les maladies neurodégénératives. Par conséquent, une approche alternative pour développer des nouveaux médicaments serait se cibler les voies de signalisation métaboliques perturbées dans les modèles de maladie d’Alzheimer. L’AMPK (AMP activated protein kinase) est une enzyme activée par les bas niveaux d’énergie cellulaire via la détection du taux AMP : ATP. Une fois activée, l’AMPK allonge la durée de vie d’organismes modèles et protège contre le développement de pathologies liées à l’âge telle que les maladies neurodégénératives. De plus, l’AMPK régule l’homéostasie mitochondriale et les réseaux mitochondriaux chez les mammifères. Cependant, il reste à savoir si l’AMPK protège contre le développement de pathologies neurodégénératives via la régulation de la structure mitochondriale. Lors de ces travaux, nous avons utilisé un protocole d’apprentissage et de mémoire chez C. elegans pour mesurer la fonction neuronale. Nous avons montré que les nématodes exprimant le peptide amyloïde Aβ1-42 dans les neurones avait une capacité d’apprentissage détériorée. Ce déficit a pu être restauré par l’activation constitutionnelle de l’AMPK. Nous montrons également que l’activation de l’AMPK améliore les capacités d’apprentissage des nématodes sauvages en induisant la fusion des mitochondries. En effet, les vers mutés pour le gène responsable de la fusion mitochondriale ont une capacité d’apprentissage diminuée, laquelle peut être restaurée par le rétablissement de la fusion mitochondriale, spécifiquement dans les neurones. Des résultats supplémentaires suggèrent que l’AMPK induirait ses effets bénéfiques sur la fonction neuronale en inhibant le facteur de transcription CRTC-1 (CREB-regulated transcriptional co-activator 1). Nos résultats tendent à montrer que cibler le métabolisme cellulaire neuronal représenterait une option thérapeutique viable afin de maintenir les fonctions neuronales dans le cadre de pathologies neurodégénératives. / The dramatic increase in life expectancy during the 20th century was accompanied by a resultant epidemic of age-related pathologies including neurodegenerative diseases. Unfortunately, current therapeutics primarily focusing on protein misfolding aspects of diseases such as Alzheimer’s Disease (AD) have been unsuccessful in the clinical trials. Recent epidemiological studies have suggested a strong association between metabolic dysfunction and neurodegeneration. Therefore, an alternative approach is to target metabolic pathways disrupted in AD models for therapeutics. AMP activated protein kinase (AMPK) is activated in a low energy state via sensing the AMP: ATP ratio. Once active, AMPK promotes longevity in model organism and protects against a wide range of age related diseases including neurodegenerative diseases. In addition, AMPK regulates mitochondrial homeostasis and mitochondrial networks in mammals. However, whether mitochondrial regulation causally links AMPK to protection against neurodegenerative disease is unknown. Here we use a learning and memory protocol in C. elegans as readout of neuronal function. We show that nematodes expressing the toxic amyloid peptide Aβ1-42 in the neurons display impaired learning ability, which can be rescued by constitutive activation of AMPK (CA-AMPK). We further show that CA-AMPK enhances learning ability in wild type nematodes by promoting mitochondrial fusion. Indeed, fusion deficient worms show impaired learning, which can be rescued by restoring mitochondrial fusion specifically in the neurons. Additional results suggest that AMPK might promote its beneficial effects on neuronal function via inhibition of CREBregulated transcriptional co-activator 1 (CRTC-1). Our results show that targeting neuronal metabolism may be a viable therapeutic option to restore neuronal function in the context of neurodegenerative diseases.

Lipids carry out important structural as well as signaling functions in the cell. In recent years, enzymes that metabolize lipids have been emerging as key regulators of basic cellular functions and developmental processes. In order to study metabolism of lipids, we have focused our research on a class of proteins: the cytochrome P450s (CYPs), which are involved in lipid production in many organisms. We have used C. elegans, a classical genetic model system, to investigate lipid metabolism because this nematode offers several technical advantages that render it suitable for our investigations. The aim of our project was to identify and characterize essential lipids for the development of worms. We have performed RNAi (RNA interference) against C. elegans CYP31A, and found that silencing of this enzyme leads to the arrest of embryonic development. Further characterization of this embryonic lethal phenotype revealed that it is caused by problems in establishment of polarity and failure in the extrusion of a polar body. Moreover, we found that embryos depleted of CYP31A are osmotic sensitive and their eggs are permeable to dyes (hoechst, FM 4-64 etc.). The defects described above are common to a class of mutants that received the denomination of POD (for Polarity and Osmotic Defects). Analysis by electron microscopy demonstrated that cyp31A(RNAi) embryos exhibit an improperly constructed eggshell. Further functional studies have demonstrated that the defects observed in cyp31A(RNAi) embryos can be ascribed to the malfunctioning of one of the three layers of the eggshell: the lipid-rich layer, but additional problems in the assembling of the other two layers are also present. In order to identify the product of CYP31A, we set up a bioassay in which we tested the capability of lipidic extract from wild type embryos to rescue the embryonic lethality. The bioassay provided a method to track the activity and allowed us to enrich the metabolic product of CYP31A by the fractionation of the total lipid extract. Another POD gene, emb-8, codes for an NADPH CYP reductase. This 4 protein supplies electrons to the CYPs for their metabolic reactions. A mutant of emb-8 (emb-8(hc69)), gives a similar phenotype as the knockdown CYP31A. With the aim to test if EMB-8 and CYP31A act in the same pathway we extracted lipids from emb-8TS mutants. We tested in the bioassay if extracts from emb-8(hc69) mutants, containing the metabolic product of CYP31A, can rescue cyp31A(RNAi) phenotype. The results obtained suggest that EMB-8 and CYP31A work in the same metabolic pathway. Conclusively, CYP31A and EMB-8 cooperate to produce a class of lipids that are required for the construction of a functional eggshell. A defective eggshell causes failure in polarity establishment, extrusion of the polar bodies, osmotic sensitivity and permeability and eventually it leads to the arrest of the development of C. elegans embryos.