Jinx, an MCMV susceptibility phenotype caused by disruption of Unc13d: a mouse model of type 3 familial hemophagocytic lymphohistiocytosis

Mouse cytomegalovirus (MCMV) susceptibility often results from defects of natural killer (NK) cell function. Here we describe Jinx, an N-ethyl-N-nitrosourea–induced MCMV susceptibility mutation that permits unchecked proliferation of the virus, causing death. In Jinx homozygotes, activated NK cells and cytotoxic T lymphocytes (CTLs) fail to degranulate, although they retain the ability to produce cytokines, and cytokine levels are markedly elevated in the blood of infected mutant mice. Jinx was mapped to mouse chromosome 11 on a total of 246 meioses and confined to a 4.60–million basepair critical region encompassing 122 annotated genes. The phenotype was ascribed to the creation of a novel donor splice site in Unc13d, the mouse orthologue of human MUNC13-4, in which mutations cause type 3 familial hemophagocytic lymphohistiocytosis (FHL3), a fatal disease marked by massive hepatosplenomegaly, anemia, and thrombocytopenia. Jinx mice do not spontaneously develop clinical features of hemophagocytic lymphohistiocytosis (HLH), but do so when infected with lymphocytic choriomeningitis virus, exhibiting hyperactivation of CTLs and antigen-presenting cells, and inadequate restriction of viral proliferation. In contrast, neither Listeria monocytogenes nor MCMV induces the syndrome. In mice, the HLH phenotype is conditional, which suggests the existence of a specific infectious trigger of FHL3 in humans

Hypopigmentation and Maternal-Zygotic Embryonic Lethality Caused by a Hypomorphic Mbtps1 Mutation in Mice

The site 1 protease, encoded by Mbtps1, mediates the initial cleavage of site 2 protease substrates, including sterol regulatory element binding proteins and CREB/ATF transcription factors. We demonstrate that a hypomorphic mutation of Mbtps1 called woodrat (wrt) caused hypocholesterolemia, as well as progressive hypopigmentation of the coat, that appears to be mechanistically unrelated. Hypopigmentation was rescued by transgenic expression of wild-type Mbtps1, and reciprocal grafting studies showed that normal pigmentation depended upon both cell-intrinsic or paracrine factors, as well as factors that act systemically, both of which are lacking in wrt homozygotes. Mbtps1 exhibited a maternal-zygotic effect characterized by fully penetrant embryonic lethality of maternal-zygotic wrt mutant offspring and partial embryonic lethality (~40%) of zygotic wrt mutant offspring. Mbtps1 is one of two maternal-zygotic effect genes identified in mammals to date. It functions nonredundantly in pigmentation and embryogenesis

La Réponse immunitaire humorale de la drosophile (Analyse génétique par mutagenèse systématique à l'EMS)

Les Insectes se défendent contre les agressions microbiennes par un ensemble de réactions très efficaces qui comportent la synthèse de peptides antimicrobiens à large spectre d'activité. Une étude génétique menée chez la drosophile a montré qu'au moins deux voies indépendantes contrôlent l'expression des peptides antimicrobiens : la voie Toll qui régule la réponse antifongique, et la voie imd qui est responsable de l'activation de la réponse antibactérienne.De nombreux aspects de la régulation de la réponse innée de la drosophile restaient à élucider : quels sont les mécanismes de reconnaissance des pathogènes? Quelles sont les cascades d'activation dans l'hémolymphe induites par cette reconnaissance? Quels sont les acteurs non encore identifiés des voies imd et Toll? Pour tenter de répondre à ces questions, l'équipe au sein de laquelle j'ai effectué ce travail de thèse a mis en oeuvre une mutagenèse saturante à l'EMS (Ethyle Méthane Sulfonate) du chromosome II de drosophile. Cette approche a pour but d'isoler tous les gènes du chromosome II impliqués dans la régulation de l'expression des peptides antimicrobiens. Lors de la mutagenèse, nous avons réalisé plus de 27000 croisements et établi 7600 lignées homozygotes pour des mutations du chromosome II. Le crible des mutants a permis d'isoler plusieurs souches mutantes de drosophiles dont la réponse innée est affectée. Les résultats issus de l'analyse de deux de ces mutants nous ont permis de montrer que Dif, un facteur de transcription de la famille Rel, est un médiateur essentiel de la réponse antifongique et contre certaines bactéries (Gram positif). De plus, nous avons isolé des mutations dans kenny, qui sont caractérisées par une perte de réponse aux infections bactériennes (Gram négatif). Ainsi, l'identification de nouveaux gènes de la réponse immunitaire de la drosophile a contribué à démontrer que les voies Toll et imd sont largement indépendantes au niveau de la transduction du signal.Insects are able to mount an efficient host defense to fight against microbial infections. A hallmark of their immune response is the synthesis and release in the hemolymph of a cocktail of antimicrobial peptides. Genetic studies have shown that, in Drosophila, at least two independent pathways control the expression of antimicrobial peptides : the Toll pathway, that regulates the antifungal response, and the imd pathway, that is responsible for the antibacterial response.Nevertheless, some aspects of the regulation of the immune response remained to be elucidated : what are the mechanisms that allow self versus self-non self recognition? What are the components of the activating cascades through hemolymph that signal the presence of pathogens? Which are the members of the imd and Toll pathways that are still unknown? To address these questions, the team in which I accomplished my Ph.D. thesis realized an EMS (Ethyl Methan Sulfonate) mutagenesis screen of the second chromosome of Drosophila. The aim of this approach is to identify all the genes involved in the regulation of the antimicrobial peptide genes expression. During the mutagenesis screen, we performed more than 27000 crosses and established 7600 fly strains homozygote for mutations carried by the second chromosome. Screening these mutants allowed us to recover several Drosophila lines affected either in the antifungal or the antibacterial response. Analysis of these mutants suggest that the two distinct pathways controlling Drosophila immune response result in the activation of two different Rel proteins : Dif (antifungal pathway) and Relish (antibacterial pathway). The cloning of the genes identified during the screen allowed us to show that the two pathways mediating antimicrobial immune response in Drosophila are largely independant.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Role of Drosophila IKK gamma in a toll-independent antibacterial immune response

We have generated, by ethylmethane sulfonate mutagenesis, loss-of-function mutants in the Drosophila homolog of the mammalian I-kappa B kinase (IKK) complex component IKK gamma (also called NEMO). Our data show that Drosophila IKK gamma is required for the Relish-dependent immune induction of the genes encoding antibacterial peptides and for resistance to infections by Escherichia coli. However, it is not required for the Toll-DIF-dependent antifungal host defense. The results indicate distinct control mechanisms of the Rel-like transactivators DIF and Relish in the Drosophila innate immune response and show that Drosophila Toll does not signal through a IKK gamma-dependent signaling complex. Thus, in contrast to the vertebrate inflammatory response, IKK gamma is required for the activation of only one immune signaling pathway in Drosophila

Premotor cortex is sensitive to auditory–visual congruence for biological motion

The auditory and visual perception systems have developed special processing strategies for ecologically valid motion stimuli, utilizing some of the statistical properties of the real world. A well-known example is the perception of biological motion, for example, the perception of a human walker. The aim of the current study was to identify the cortical network involved in the integration of auditory and visual biological motion signals. We first determined the cortical regions of auditory and visual coactivation (Experiment 1); a conjunction analysis based on unimodal brain activations identified four regions: middle temporal area, inferior parietal lobule, ventral premotor cortex, and cerebellum. The brain activations arising from bimodal motion stimuli (Experiment 2) were then analyzed within these regions of coactivation. Auditory footsteps were presented concurrently with either an intact visual point-light walker (biological motion) or a scrambled point-light walker; auditory and visual motion in depth (walking direction) could either be congruent or incongruent. Our main finding is that motion incongruency (across modalities) increases the activity in the ventral premotor cortex, but only if the visual point-light walker is intact. Our results extend our current knowledge by providing new evidence consistent with the idea that the premotor area assimilates information across the auditory and visual modalities by comparing the incoming sensory input with an internal representation