Innate immune basis for rift valley fever susceptibility in mouse models

Rift Valley fever virus (RVFV) leads to varied clinical manifestations in animals and in humans that range from moderate fever to fatal illness, suggesting that host immune responses are important determinants of the disease severity. We investigated the immune basis for the extreme susceptibility of MBT/Pas mice that die with mild to acute hepatitis by day 3 post-infection compared to more resistant BALB/cByJ mice that survive up to a week longer. Lower levels of neutrophils observed in the bone marrow and blood of infected MBT/Pas mice are unlikely to be causative of increased RVFV susceptibility as constitutive neutropenia in specific mutant mice did not change survival outcome. However, whereas MBT/Pas mice mounted an earlier inflammatory response accompanied by higher amounts of interferon (IFN)-α in the serum compared to BALB/cByJ mice, they failed to prevent high viral antigen load. Several immunological alterations were uncovered in infected MBT/Pas mice compared to BALB/cByJ mice, including low levels of leukocytes that expressed type I IFN receptor subunit 1 (IFNAR1) in the blood, spleen and liver, delayed leukocyte activation and decreased percentage of IFN-γ-producing leukocytes in the blood. These observations are consistent with the complex mode of inheritance of RVFV susceptibility in genetic studies

Innate immune basis for rift valley fever susceptibility in mouse models

Rift Valley fever virus (RVFV) leads to varied clinical manifestations in animals and in humans that range from moderate fever to fatal illness, suggesting that host immune responses are important determinants of the disease severity. We investigated the immune basis for the extreme susceptibility of MBT/Pas mice that die with mild to acute hepatitis by day 3 post-infection compared to more resistant BALB/cByJ mice that survive up to a week longer. Lower levels of neutrophils observed in the bone marrow and blood of infected MBT/Pas mice are unlikely to be causative of increased RVFV susceptibility as constitutive neutropenia in specific mutant mice did not change survival outcome. However, whereas MBT/Pas mice mounted an earlier inflammatory response accompanied by higher amounts of interferon (IFN)-α in the serum compared to BALB/cByJ mice, they failed to prevent high viral antigen load. Several immunological alterations were uncovered in infected MBT/Pas mice compared to BALB/cByJ mice, including low levels of leukocytes that expressed type I IFN receptor subunit 1 (IFNAR1) in the blood, spleen and liver, delayed leukocyte activation and decreased percentage of IFN-γ-producing leukocytes in the blood. These observations are consistent with the complex mode of inheritance of RVFV susceptibility in genetic studies

I-SceI-Mediated Double-Strand Break Does Not Increase the Frequency of Homologous Recombination at the Dct Locus in Mouse Embryonic Stem Cells

Targeted induction of double-strand breaks (DSBs) at natural endogenous loci was shown to increase the rate of gene replacement by homologous recombination in mouse embryonic stem cells. The gene encoding dopachrome tautomerase (Dct) is specifically expressed in melanocytes and their precursors. To construct a genetic tool allowing the replacement of Dct gene by any gene of interest, we generated an embryonic stem cell line carrying the recognition site for the yeast I-SceI meganuclease embedded in the Dct genomic segment. The embryonic stem cell line was electroporated with an I-SceI expression plasmid, and a template for the DSB-repair process that carried sequence homologies to the Dct target. The I-SceI meganuclease was indeed able to introduce a DSB at the Dct locus in live embryonic stem cells. However, the level of gene targeting was not improved by the DSB induction, indicating a limited capacity of I-SceI to mediate homologous recombination at the Dct locus. These data suggest that homologous recombination by meganuclease-induced DSB may be locus dependent in mammalian cells

La cartographie des genes chez la souris par etude du polymorphisme de restriction

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Transgenic expression of full-length 2',5'-oligoadenylate synthetase 1b confers to BALB/c mice resistance against West Nile virus-induced encephalitis.

International audienceSusceptibility of inbred strains to infection with West Nile virus (WNV) has been genetically associated with an arginine-to-a nonsense codon substitution at position 253 (R253X) in the predicted sequence of the murine 2',5'-oligoadenylate synthetase 1B (OAS1B) protein. We introduced by transgenesis the Oas1b cDNA from MBT/Pas mice carrying the R253 codon (Oas1b(MBT)) into BALB/c mice homozygous for the X253 allele (Oas1b(BALB/c)). Overexpression of Oas1b(MBT) mRNA in the brain of transgenic mice prior and in the time course of infection provided protection against the neuroinvasive WNV strain IS-98-ST1. A 200-fold induction of Oas1b(MBT) mRNA in the brain of congenic BALB/c mice homozygous for a MBT/Pas segment encompassing the Oas1b gene was also efficient in reducing both viral growth and mortality, whereas a 200-fold induction of Oas1b(BALB/c) mRNA was unable to prevent virally-induced encephalitis, confirming the critical role of the R253X mutation on Oas1b activity in live mice

Mutations in the gene encoding the low-density lipoprotein receptor LRP4 cause abnormal limb development in the mouse

International audiencePositional cloning of two recessive mutations of the mouse that cause polysyndactyly (dan and mdig-Chr 2) confirmed that the gene encoding MEGF7/LRP4, a member of the low-density lipoprotein receptor family, plays an essential role in the process of digit differentiation. Pathologies observed in the mutant mice provide insight into understanding the function(s) of LRP4 as a negative regulator of the Wnt-beta-catenin signaling pathway and may help identify the genetic basis for common human disorders with similar phenotypes

The ring finger protein 213 gene (Rnf213) contributes to Rift Valley fever resistance in mice

International audienceRift Valley fever (RVF) is an emerging viral zoonosis that primarily affects ruminants and humans. We have previously shown that wild-derived MBT/Pas mice are highly susceptible to RVF virus and that part of this phenotype is controlled by a locus located on distal Chromosome 11. Using congenic strains, we narrowed down the critical interval to a 530 kb region containing five protein-coding genes among which Rnf213 emerged as a potential candidate. We generated Rnf213-deficient mice by CRISPR/CAS9 on the C57BL/6J background and showed that they were significantly more susceptible to RVF than control mice, with an average survival time post-infection reduced from 7 to 4 days. The human RNF213 gene had been associated with the cerebrovascular Moyamoya disease (MMD or MYMY) but the inactivation of this gene in the mouse resulted only in mild anomalies of the neovascularization. This study provides the first evidence that the Rnf213 gene may also impact the resistance to infectious diseases such as RVF

Assignment of the chromogranin A (Chga) locus to homologous regions on mouse chromosome 12 and rat chromosome 6.

Chromogranin A is an acidic protein, stored and released with catecholamines, and is overexpressed in genetic hypertension. In the human genome, its locus has previously been positioned on the long arm of Chromosome 14 in the 14q32 region. As a first step toward evaluating its potential linkage with hereditary hypertension, we determined its chromosomal position in mouse and rat. Chromogranin A was present as a single-copy gene in both mouse and rat. Analysis of the allele distribution in an interspecific mouse backcross by single-strand conformation polymorphism positioned the chromogranin A locus on Chromosome 12, between Igh-C and D12Pas1. Evaluation of a rat/mouse somatic cell hybrid panel indicated that chromogranin A is on rat Chromosome 6. In each case (mouse, rat, and human), chromogranin A is in a conserved region with nearby markers including the immunoglobulin heavy chain locus.Comparative StudyJournal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Genetic dissection of Rift Valley fever pathogenesis: Rvfs2 locus on mouse chromosome 11 enables survival to early-onset hepatitis

International audienceInfection of mice with Rift Valley fever virus (RVFV) reproduces major pathological features of severe human disease, notably the early-onset hepatitis and delayed-onset encephalitis. We previously reported that the Rvfs2 locus from the susceptible MBT/Pas strain reduces survival time after RVFV infection. Here, we used BALB/cByJ (BALB) mice congenic for Rvfs2 (C.MBT-Rvfs2) to investigate the pathophysiological mechanisms impacted by Rvfs2. Clinical, biochemical and histopathological features indicated similar liver damage in BALB and C.MBT-Rvfs2 mice until day 5 after infection. However, while C.MBT-Rvfs2 mice succumbed from acute liver injury, most BALB mice recovered and died later of encephalitis. Hepatocytes of BALB infected liver proliferated actively on day 6, promoting organ regeneration and recovery from liver damage. By comparison with C.MBT-Rvfs2, BALB mice had up to 100-fold lower production of infectious virions in the peripheral blood and liver, strongly decreased RVFV protein in liver and reduced viral replication in primary cultured hepatocytes, suggesting that the BALB Rvfs2 haplotype limits RVFV pathogenicity through decreased virus replication. Moreover, bone marrow chimera experiments showed that both hematopoietic and non-hematopoietic cells are required for the protective effect of the BALB Rvfs2 haplotype. Altogether, these results indicate that Rvfs2 controls critical events which allow survival to RVFV-induced hepatitis

Frequency of homologous recombination at the <i>Dct</i> locus.

<p>Frequency of homologous recombination at the <i>Dct</i> locus.</p