The antitumoral effects of chemerin are independent from leukocyte recruitment and mediated by inhibition of neoangiogenesis

Chemerin, a multifunctional protein acting through the receptor ChemR23/CMKLR1, is downregulated in various human tumors and was shown to display antitumoral properties in mouse models of cancer. In the present study, we report that bioactive chemerin expression by tumor cells delays the growth of B16 melanoma and Lewis lung carcinoma in vivo. A similar delay is observed when chemerin is not expressed by tumor cells but by keratinocytes of the host mice. The protective effect of chemerin is mediated by CMKLR1 and appears unrelated to the recruitment of leukocyte populations. Rather, tumors grown in the presence of chemerin display a much smaller number of blood vessels, hypoxic regions early in their development, and larger necrotic areas. These observations likely explain the slower growth of the tumors. The anti-angiogenic effects of chemerin were confirmed in a bead sprouting assay using human umbilical vein endothelial cells. These results suggest that CMKLR1 agonists might constitute therapeutic molecules inhibiting the neoangiogenesis process in solid tumors.

The HSP90/R2TP assembly chaperone promotes cell proliferation in the intestinal epithelium

The R2TP chaperone cooperates with HSP90 to integrate newly synthesized proteins into multi-subunit complexes, yet its role in tissue homeostasis is unknown. Here, we generated conditional, inducible knock-out mice for Rpap3 to inactivate this core component of R2TP in the intestinal epithelium. In adult mice, Rpap3 invalidation caused destruction of the small intestinal epithelium and death within 10 days. Levels of R2TP substrates decreased, with strong effects on mTOR, ATM and ATR. Proliferative stem cells and progenitors deficient for Rpap3 failed to import RNA polymerase II into the nucleus and they induced p53, cell cycle arrest and apoptosis. Post-mitotic, differentiated cells did not display these alterations, suggesting that R2TP clients are preferentially built in actively proliferating cells. In addition, high RPAP3 levels in colorectal tumors from patients correlate with bad prognosis. Here, we show that, in the intestine, the R2TP chaperone plays essential roles in normal and tumoral proliferation.

Dynamics of myogenic differentiation using a novel Myogenin knock-in reporter mouse

Background

Myogenin is a transcription factor that is expressed during terminal myoblast differentiation in embryonic development and adult muscle regeneration. Investigation of this cell state transition has been hampered by the lack of a sensitive reporter to dynamically track cells during differentiation.

Results

Here, we report a knock-in mouse line expressing the tdTOMATO fluorescent protein from the endogenous Myogenin locus. Expression of tdTOMATO in Myog^ntdTom mice recapitulated endogenous Myogenin expression during embryonic muscle formation and adult regeneration and enabled the isolation of the MYOGENIN⁺ cell population. We also show that tdTOMATO fluorescence allows tracking of differentiating myoblasts in vitro and by intravital imaging in vivo. Lastly, we monitored by live imaging the cell division dynamics of differentiating myoblasts in vitro and showed that a fraction of the MYOGENIN⁺ population can undergo one round of cell division, albeit at a much lower frequency than MYOGENIN⁻ myoblasts.

Conclusions

We expect that this reporter mouse will be a valuable resource for researchers investigating skeletal muscle biology in developmental and adult contexts.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13395-021-00260-x.

Corrigendum: Expression of Bioactive Chemerin by Keratinocytes Inhibits Late Stages of Tumor Development in a Chemical Model of Skin Carcinogenesis

[This corrects the article DOI: 10.3389/fonc.2019.01253.].

Expression of Bioactive Chemerin by Keratinocytes Inhibits Late Stages of Tumor Development in a Chemical Model of Skin Carcinogenesis

Chemerin is a multifunctional protein acting mainly through the G protein-coupled receptor ChemR23/CMKLR1/Chemerin₁. Its expression is frequently downregulated in human tumors, including in melanoma and squamous cell carcinoma of the skin and anti-tumoral properties of chemerin were reported in mouse tumor graft models. In the present study, we report the development of spontaneous skin tumors in aged ChemR23-deficient mice. In order to test the potential therapeutic benefit of chemerin analogs, a transgenic model in which bioactive chemerin is over-expressed by basal keratinocytes was generated. These animals are characterized by increased levels of chemerin immunoreactivity and bioactivity in the skin and the circulation. In a chemical carcinogenesis model, papillomas developed later, were less numerous, and their progression to carcinomas was delayed. Temporal control of chemerin expression by doxycycline allowed to attribute its effects to late stages of carcinogenesis. The protective effects of chemerin were partly abrogated by ChemR23 invalidation. These results demonstrate that chemerin is able to delay very significantly tumor progression in a model that recapitulates closely the evolution of solid cancer types in human and suggest that the chemerin-ChemR23 system might constitute an interesting target for therapeutic intervention in the cancer field.

A distinct cardiopharyngeal mesoderm genetic hierarchy establishes antero-posterior patterning of esophagus striated muscle

In most vertebrates, the upper digestive tract is composed of muscularized jaws linked to the esophagus that permits food ingestion and swallowing. Masticatory and esophagus striated muscles (ESM) share a common cardiopharyngeal mesoderm (CPM) origin, however ESM are unusual among striated muscles as they are established in the absence of a primary skeletal muscle scaffold. Using mouse chimeras, we show that the transcription factors Tbx1 and Isl1 are required cell-autonomously for myogenic specification of ESM progenitors. Further, genetic loss-of-function and pharmacological studies point to MET/HGF signaling for antero-posterior migration of esophagus muscle progenitors, where Hgf ligand is expressed in adjacent smooth muscle cells. These observations highlight the functional relevance of a smooth and striated muscle progenitor dialogue for ESM patterning. Our findings establish a Tbx1-Isl1-Met genetic hierarchy that uniquely regulates esophagus myogenesis and identify distinct genetic signatures that can be used as framework to interpret pathologies arising within CPM derivatives.

The HERC2 ubiquitin ligase is essential for embryonic development and regulates motor coordination

A mutation in the HERC2 gene has been linked to a severe neurodevelopmental disorder with similarities to the Angelman syndrome. This gene codifies a protein with ubiquitin ligase activity that regulates the activity of tumor protein p53 and is involved in important cellular processes such as DNA repair, cell cycle, cancer, and iron metabolism. Despite the critical role of HERC2 in these physiological and pathological processes, little is known about its relevance in vivo. Here, we described a mouse with targeted inactivation of the Herc2 gene. Homozygous mice were not viable. Distinct from other ubiquitin ligases that interact with p53, such as MDM2 or MDM4, p53 depletion did not rescue the lethality of homozygous mice. The HERC2 protein levels were reduced by approximately one-half in heterozygous mice. Consequently, HERC2 activities, including ubiquitin ligase and stimulation of p53 activity, were lower in heterozygous mice. A decrease in HERC2 activities was also observed in human skin fibroblasts from individuals with an Angelman-like syndrome that express an unstable mutant protein of HERC2. Behavioural analysis of heterozygous mice identified an impaired motor synchronization with normal neuromuscular function. This effect was not observed in p53 knockout mice, indicating that a mechanism independent of p53 activity is involved. Morphological analysis showed the presence of HERC2 in Purkinje cells and a specific loss of these neurons in the cerebella of heterozygous mice. In these animals, an increase of autophagosomes and lysosomes was observed. Our findings establish a crucial role of HERC2 in embryonic development and motor coordination.

Electrochemical immunosensor for simultaneous determination of interleukin-1 beta and tumor necrosis factor alpha in serum and saliva using dual screen printed electrodes modified with functionalized double-walled carbon nanotubes

Dual screen-printed carbon electrodes modified with 4-carboxyphenyl-functionalized double-walled carbon nanotubes (HOOC-Phe-DWCNTs/SPCEs) have been used as scaffolds for the preparation of electrochemical immunosensors for the simultaneous determination of the cytokines Interleukin-1β (IL-1β) and factor necrosis tumor α (TNF-α). IL-1β. Capture antibodies were immobilized onto HOOC-Phe-DWCNTs/SPCEs in an oriented form making using the commercial polymeric coating Mix&Go™. Sandwich type immunoassays with amperometric signal amplification through the use of poly-HRP-streptavidin conjugates and H₂O₂ as HRP substrate and hydroquinone as redox mediator were implemented. Upon optimization of the experimental variables affecting the immunosensor performance, the dual immunosensor allows ranges of linearity extending between 0.5 and 100 pg/mL and from 1 to 200 pg/mL for IL-1β and TNF-α, respectively, these ranges being adequate for the determination of the cytokines in clinical samples. The achieved limits of detection were 0.38 pg/mL (IL-1β) and 0.85 pg/mL (TNF-α). In addition, the dual immunosensor exhibits excellent reproducibility of the measurements, storage stability of the anti-IL-Phe-DWCNTs/SPCE and anti-TNF-Phe-DWCNTs/SPCE conjugates, and selectivity as well as negligible cross-talking. The dual immunosensor was applied to the simultaneous determination of IL-1β and TNF-α in human serum spiked at clinically relevant concentration levels and in real saliva samples.

Implementation of meiosis prophase I programme requires a conserved retinoid-independent stabilizer of meiotic transcripts

Sexual reproduction is crucially dependent on meiosis, a conserved, specialized cell division programme that is essential for the production of haploid gametes. Here we demonstrate that fertility and the implementation of the meiotic programme require a previously uncharacterized meiosis-specific protein, MEIOC. Meioc invalidation in mice induces early and pleiotropic meiotic defects in males and females. MEIOC prevents meiotic transcript degradation and interacts with an RNA helicase that binds numerous meiotic mRNAs. Our results indicate that proper engagement into meiosis necessitates the specific stabilization of meiotic transcripts, a previously little-appreciated feature in mammals. Remarkably, the upregulation of MEIOC at the onset of meiosis does not require retinoic acid and STRA8 signalling. Thus, we propose that the complete induction of the meiotic programme requires both retinoic acid-dependent and -independent mechanisms. The latter process involving post-transcriptional regulation likely represents an ancestral mechanism, given that MEIOC homologues are conserved throughout multicellular animals.

Meiosis is a cell division program that produces haploid gametes and is initiated by a retinoic acid-dependent process. Here the authors report that a meiosis-specific protein, MEIOC, is upregulated in a retinoic acid-independent manner and is required to stabilise meiosis-specific transcripts.

Covalent functionalization of N-doped graphene by N-alkylation

N-Functionalization of N-graphene is described by the first time. It can be efficiently achieved combining phase transfer catalysis and microwave irradiation. The influence of functionalization on the optical band gap is studied.

Cellular and behavioral outcomes of dorsal striatonigral neuron ablation: new insights into striatal functions

The striatum is the input structure of the basal ganglia network that contains heterogeneous neuronal populations, including two populations of projecting neurons called the medium spiny neurons (MSNs), and different types of interneurons. We developed a transgenic mouse model enabling inducible ablation of the striatonigral MSNs constituting the direct pathway by expressing the human diphtheria toxin (DT) receptor under the control of the Slc35d3 gene promoter, a gene enriched in striatonigral MSNs. DT injection into the striatum triggered selective elimination of the majority of striatonigral MSNs. DT-mediated ablation of striatonigral MSNs caused selective loss of cholinergic interneurons in the dorsal striatum but not in the ventral striatum (nucleus accumbens), suggesting a region-specific critical role of the direct pathway in striatal cholinergic neuron homeostasis. Mice with DT injection into the dorsal striatum showed altered basal and cocaine-induced locomotion and dramatic reduction of L-DOPA-induced dyskinesia in the parkinsonian condition. In addition, these mice exhibited reduced anxiety, revealing a role of the dorsal striatum in the modulation of behaviors involving an emotional component, behaviors generally associated with limbic structures. Altogether, these results highlight the implication of the direct striatonigral pathway in the regulation of heterogeneous functions from cell survival to regulation of motor and emotion-associated behaviors.

Human hematopoietic reconstitution and HLA-restricted responses in nonpermissive alymphoid mice

We generated a new humanized mouse model to study HLA-restricted immune responses. For this purpose, we created unique murine hosts by enforcing the expression of human SIRPα by murine phagocytes in murine MHC-deficient HLA-transgenic alymphoid hosts, an approach that allowed the immune reconstitution of nonpermissive mice following injection of human hematopoietic stem cells. We showed that these mouse/human chimeras were able to generate HLA-restricted responses to immunization. These new humanized mice may offer attractive models to study immune responses to human diseases, such as HIV and EBV infections, as well as to assay new vaccine strategies.

A novel nodal enhancer dependent on pluripotency factors and smad2/3 signaling conditions a regulatory switch during epiblast maturation

HBE, a newly discovered enhancer element, mediates the influence of pluripotency factors and Activin/Nodal signaling on early Nodal expression in the mouse embryo, and controls the activation of later-acting Nodal enhancers.

During early development, modulations in the expression of Nodal, a TGFβ family member, determine the specification of embryonic and extra-embryonic cell identities. Nodal has been extensively studied in the mouse, but aspects of its early expression remain unaccounted for. We identified a conserved hotspot for the binding of pluripotency factors at the Nodal locus and called this sequence “highly bound element” (HBE). Luciferase-based assays, the analysis of fluorescent HBE reporter transgenes, and a conditional mutation of HBE allowed us to establish that HBE behaves as an enhancer, is activated ahead of other Nodal enhancers in the epiblast, and is essential to Nodal expression in embryonic stem cells (ESCs) and in the mouse embryo. We also showed that HBE enhancer activity is critically dependent on its interaction with the pluripotency factor Oct4 and on Activin/Nodal signaling. Use of an in vitro model of epiblast maturation, relying on the differentiation of ESCs into epiblast stem cells (EpiSCs), revealed that this process entails a shift in the regulation of Nodal expression from an HBE-driven phase to an ASE-driven phase, ASE being another autoregulatory Nodal enhancer. Deletion of HBE in ESCs or in EpiSCs allowed us to show that HBE, although not necessary for Nodal expression in EpiSCs, is required in differentiating ESCs to activate the differentiation-promoting ASE and therefore controls this regulatory shift. Our findings clarify how early Nodal expression is regulated and suggest how this regulation can promote the specification of extra-embryonic precusors without inducing premature differentiation of epiblast cells. More generally, they open new perspectives on how pluripotency factors achieve their function.

In the early mouse embryo, Nodal, a member of the TGFbeta superfamily of signalling proteins, promotes the differentiation of extra-embryonic tissues, as well as tissues within the developing embryo itself. Characterising the regulation of Nodal gene expression is essential to understand how Nodal signals in diverse tissue types and at different stages of embryonic development. Four distinct enhancer sequences have been shown to regulate Nodal expression, although none could account for it in the preimplantation epiblast or in embryonic stem cells. We identified a novel enhancer, HBE, responsible for the earliest aspects of Nodal expression. We show that activation of HBE depends on its interaction with a well-known pluripotency factor called Oct4. HBE itself also controls the activation of at least one other Nodal enhancer. Our findings clarify how early Nodal expression is regulated and reveal how pluripotency factors may control the onset of differentiation in embryonic tissues.

Protective role of LGP2 in influenza virus pathogenesis

Influenza A virus triggers a contagious respiratory disease that can cause considerable morbidity and mortality. Using an in vitro approach, we previously demonstrated that the pattern recognition receptor retinoic acid-inducible gene I (RIG-I) plays a key role in influenza A virus-mediated immune response. However, the importance of RIG-I signaling in vivo has not been thoroughly examined, because of the lack of an appropriate mouse models. To circumvent this issue, we generated a new transgenic mouse overexpressing LGP2 (hereafter, "LGP2 TG mice"), a major regulator of the RIG-I signaling pathway. The time course of several parameters was compared in infected wild-type and LGP2 TG mice. We found that LGP2 TG mice displayed significantly reduced inflammatory mediators and a lower leukocyte infiltration into the bronchoalveolar airspace. More importantly, LGP2 TG mice had a significant survival advantage. Hence, our in vivo study reveals that LGP2 is a major downregulator of the influenza A virus-triggered detrimental inflammatory response.

Lineage tracing and genetic ablation of ADAM12(+) perivascular cells identify a major source of profibrotic cells during acute tissue injury

Profibrotic cells that develop upon injury generate permanent scar tissue and impair organ recovery, though their origin and fate are unclear. Here we show that transient expression of ADAM12 (a disintegrin and metalloprotease 12) identifies a distinct proinflammatory subset of platelet-derived growth factor receptor-α-positive stromal cells that are activated upon acute injury in the muscle and dermis. By inducible genetic fate mapping, we demonstrate in vivo that injury-induced ADAM12(+) cells are specific progenitors of a major fraction of collagen-overproducing cells generated during scarring, which are progressively eliminated during healing. Genetic ablation of ADAM12(+) cells, or knockdown of ADAM12, is sufficient to limit generation of profibrotic cells and interstitial collagen accumulation. ADAM12(+) cells induced upon injury are developmentally distinct from muscle and skin lineage cells and are derived from fetal ADAM12(+) cells programmed during vascular wall development. Thus, our data identify injury-activated profibrotic progenitors residing in the perivascular space that can be targeted through ADAM12 to limit tissue scarring.

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.

Mouse PRDM9 DNA-binding specificity determines sites of histone H3 lysine 4 trimethylation for initiation of meiotic recombination

The nature of the PRDM9 zinc finger domain determines the location of hotspots for meiotic recombination in the genome and promotes local histone H3K4 trimethylation.

Meiotic recombination generates reciprocal exchanges between homologous chromosomes (also called crossovers, COs) that are essential for proper chromosome segregation during meiosis and are a major source of genome diversity by generating new allele combinations. COs have two striking properties: they occur at specific sites, called hotspots, and these sites evolve rapidly. In mammals, the Prdm9 gene, which encodes a meiosis-specific histone H3 methyltransferase, has recently been identified as a determinant of CO hotspots. Here, using transgenic mice, we show that the sole modification of PRDM9 zinc fingers leads to changes in hotspot activity, histone H3 lysine 4 trimethylation (H3K4me3) levels, and chromosome-wide distribution of COs. We further demonstrate by an in vitro assay that the PRDM9 variant associated with hotspot activity binds specifically to DNA sequences located at the center of the three hotspots tested. Remarkably, we show that mutations in cis located at hotspot centers and associated with a decrease of hotspot activity affect PRDM9 binding. Taken together, these results provide the direct demonstration that Prdm9 is a master regulator of hotspot localization through the DNA binding specificity of its zinc finger array and that binding of PRDM9 at hotspots promotes local H3K4me3 enrichment.

Meiosis is the process of cell division that reduces the number of chromosome sets from two to one, so producing gametes for sexual reproduction. During meiosis in many organisms, there is reciprocal exchange of genetic material between homologous chromosomes by the formation of “crossovers,” which promote genetic diversity by creating new combinations of gene variants and play an important mechanical role in the segregation of chromosomes. Crossovers do not occur randomly throughout the genome, but in small regions called hotspots. Recent work showed that hotspots have specific structural features and that the protein PRDM9 is important in specifying their location. PRDM9 contains a so-called zinc finger domain that is predicted to bind specific DNA sequences, suggesting that hotspots might be sites where PRDM9 binds. By using transgenic mice expressing PRDM9 with modified zinc fingers, here we show directly that the nature of the zinc fingers in PRDM9 determines crossover hotspot localization. We show that PRDM9 binds DNA sequences at the center of hotspots. Furthermore, we identify DNA sequence polymorphisms that affect its binding and the extent of crossover activity. Overall, our work shows that PRDM9, through its zinc finger domain, is a master regulator of hotspot location in the mouse genome.

Lineage relationship analysis of RORgammat+ innate lymphoid cells

Lymphoid tissue-inducer (LTi) cells initiate the development of lymphoid tissues through the activation of local stromal cells in a process similar to inflammation. LTi cells express the nuclear hormone receptor RORγt, which also directs the expression of the proinflammatory cytokine interleukin-17 in T cells. We show here that LTi cells are part of a larger family of proinflammatory RORγt(+) innate lymphoid cells (ILCs) that differentiate from distinct fetal liver RORγt(+) precursors. The fate of RORγt(+) ILCs is determined by mouse age, and after birth, favors the generation of cells involved in intestinal homeostasis and defense. Contrary to RORγt(+) T cells, however, RORγt(+) ILCs develop in the absence of microbiota. Our study indicates that RORγt(+) ILCs evolve to preempt intestinal colonization by microbial symbionts.

Progressive Purkinje cell degeneration in tambaleante mutant mice is a consequence of a missense mutation in HERC1 E3 ubiquitin ligase

The HERC gene family encodes proteins with two characteristic domains: HECT and RCC1-like. Proteins with HECT domains have been described to function as ubiquitin ligases, and those that contain RCC1-like domains have been reported to function as GTPases regulators. These two activities are essential in a number of important cellular processes such as cell cycle, cell signaling, and membrane trafficking. Mutations affecting these domains have been found associated with retinitis pigmentosa, amyotrophic lateral sclerosis, and cancer. In humans, six HERC genes have been reported which encode two subgroups of HERC proteins: large (HERC1-2) and small (HERC3-6). The giant HERC1 protein was the first to be identified. It has been involved in membrane trafficking and cell proliferation/growth through its interactions with clathrin, M2-pyruvate kinase, and TSC2 proteins. Mutations affecting other members of the HERC family have been found to be associated with sterility and growth retardation. Here, we report the characterization of a recessive mutation named tambaleante, which causes progressive Purkinje cell degeneration leading to severe ataxia with reduced growth and lifespan in homozygous mice aged over two months. We mapped this mutation in mouse chromosome 9 and then performed positional cloning. We found a G⇔A transition at position 1448, causing a Gly to Glu substitution (Gly483Glu) in the highly conserved N-terminal RCC1-like domain of the HERC1 protein. Successful transgenic rescue, with either a mouse BAC containing the normal copy of Herc1 or with the human HERC1 cDNA, validated our findings. Histological and biochemical studies revealed extensive autophagy associated with an increase of the mutant protein level and a decrease of mTOR activity. Our observations concerning this first mutation in the Herc1 gene contribute to the functional annotation of the encoded E3 ubiquitin ligase and underline the crucial and unexpected role of this protein in Purkinje cell physiology.

The cerebellum is a coordination center whose function is to fine-tune vertebrates' gait and balance; and for this reason, alterations or damage affecting this structure result in a complex syndrome, called ataxia, with neurological signs that are easily recognized. In the mouse, many mutations producing ataxia have been identified and characterized. They have contributed to a better understanding of the genetics of cerebellum development, physiology, and pathology. The present study identifies the recessive allele responsible for the progressive and massive degeneration of the Purkinje cells observed in mutant mice previously named tambaleante. The mutation leads to a single amino acid substitution in a highly conserved domain (RCC1-like) of the giant protein HERC1. This protein belongs to the families HECT (E3 ubiquitin ligases) and RCC1 (GTPases regulators). While a variety of mutations have been reported in several members of these families, leading to sterility, growth retardation, retinitis pigmentosa, amyotrophic lateral sclerosis, or cancer, no mutation had ever been reported so far in the mouse Herc1 gene. This report demonstrates the crucial and unexpected role of HERC1 in Purkinje cell physiology that could be considered helpful in the development of new therapeutic strategies for neurodegenerative disorders.

In vivo equilibrium of proinflammatory IL-17+ and regulatory IL-10+ Foxp3+ RORgamma t+ T cells

The nuclear hormone receptor retinoic acid receptor–related orphan receptor γt (RORγt) is required for the generation of T helper 17 cells expressing the proinflammatory cytokine interleukin (IL)-17. In vivo, however, less than half of RORγt⁺ T cells express IL-17. We report here that RORγt⁺ Tαβ cells include Foxp3⁺ cells that coexist with IL-17–producing RORγt⁺ Tαβ cells in all tissues examined. The Foxp3⁺ RORγt⁺ Tαβ express IL-10 and CCL20, and function as regulatory T cells. Furthermore, the ratio of Foxp3⁺ to IL-17–producing RORγt⁺ Tαβ cells remains remarkably constant in mice enduring infection and inflammation. This equilibrium is tuned in favor of IL-10 production by Foxp3 and CCL20, and in favor of IL-17 production by IL-6 and IL-23. In the lung and skin, the largest population of RORγt⁺ T cells express the γδ T cell receptor and produce the highest levels of IL-17 independently of IL-6. Thus, potentially antagonistic proinflammatory IL-17–producing and regulatory Foxp3⁺ RORγt⁺ T cells coexist and are tightly controlled, suggesting that a perturbed equilibrium in RORγt⁺ T cells might lead to decreased immunoreactivity or, in contrast, to pathological inflammation.

Conditional knock-out reveals that zygotic vezatin-null mouse embryos die at implantation

Vezatin, a protein associated to adherens junctions in epithelial cells, is already expressed in mouse oocytes and during pre-implantation development. Using a floxed strategy to generate a vezatin-null allele, we show that the lack of zygotic vezatin is embryonic lethal, indicating that vezatin is an essential gene. Homozygous null embryos are able to elicit a decidual response but as early as day 6.0 post-coitum mutant implantation sites are devoid of embryonic structures. Mutant blastocysts are morphologically normal, but only half of them are able to hatch upon in vitro culture and the blastocyst outgrowths formed after 3.5 days in culture exhibit severe abnormalities, in particular disrupted intercellular adhesion and clear signs of cellular degeneration. Notably, the junctional proteins E-cadherin and beta-catenin are delocalized and not observed at the plasma membrane anymore. These in vitro observations reinforce the idea that homozygous vezatin-null mutants die at the time of implantation because of a defect in intercellular adhesion. Together these results indicate that the absence of zygotic vezatin is deleterious for the implantation process, most likely because cadherin-dependent intercellular adhesion is impaired in late blastocysts when the maternal vezatin is lost.

The archetypal R90C CADASIL-NOTCH3 mutation retains NOTCH3 function in vivo

Cerebral Autosomal Dominant Arteriopathy with Subcortical infarcts and Leukoencephalopathy (CADASIL) is the most prominent known cause of inherited stroke and vascular dementia in human adult. The disease gene, NOTCH3, encodes a transmembrane receptor primarily expressed in arterial smooth muscle cells (SMC). Pathogenic mutations lead to an odd number of cysteine residues within the NOTCH3 extracellular domain (NOTCH3(ECD)), and are associated with progressive accumulation of NOTCH3(ECD) at the SMC plasma membrane. The murine homolog, Notch3, is dispensable for viability but required post-natally for the elaboration and maintenance of arteries. How CADASIL-associated mutations impact NOTCH3 function remains a fundamental, yet unresolved issue. Particularly, whether NOTCH3(ECD) accumulation may titrate the ligand and inhibit the normal pathway is unknown. Herein, using genetic analyses in the mouse, we assessed the functional significance of an archetypal CADASIL-associated mutation (R90C), in vivo, in brain arteries. We show that transgenic mouse lines expressing either the wild-type human NOTCH3 or the mutant R90C human NOTCH3, at comparable and physiological levels, can rescue the arterial defects of Notch3-/- mice to similar degrees. In vivo assessment of NOTCH3/RBP-Jk activity provides evidence that the mutant NOTCH3 protein exhibits normal level of activity in brain arteries. Remarkably, the mutant NOTCH3 protein remains functional and does not exhibit dominant negative interfering activity, even when NOTCH3(ECD) accumulates. Collectively, these data suggest a model that invokes novel pathogenic roles for the mutant NOTCH3 protein rather than compromised NOTCH3 function as the primary determinant of the CADASIL arteriopathy.

Mutations in the gene encoding pejvakin, a newly identified protein of the afferent auditory pathway, cause DFNB59 auditory neuropathy

Auditory neuropathy is a particular type of hearing impairment in which neural transmission of the auditory signal is impaired, while cochlear outer hair cells remain functional. Here we report on DFNB59, a newly identified gene on chromosome 2q31.1-q31.3 mutated in four families segregating autosomal recessive auditory neuropathy. DFNB59 encodes pejvakin, a 352-residue protein. Pejvakin is a paralog of DFNA5, a protein of unknown function also involved in deafness. By immunohistofluorescence, pejvakin is detected in the cell bodies of neurons of the afferent auditory pathway. Furthermore, Dfnb59 knock-in mice, homozygous for the R183W variant identified in one DFNB59 family, show abnormal auditory brainstem responses indicative of neuronal dysfunction along the auditory pathway. Unlike previously described sensorineural deafness genes, all of which underlie cochlear cell pathologies, DFNB59 is the first human gene implicated in nonsyndromic deafness due to a neuronal defect.

Generation and phenotypic analysis of sigma receptor type I (sigma 1) knockout mice

Sigma (sigma) sites are a type of nonopiate receptor whose role has been associated with several behaviours, including anxiety, depression, analgesia, learning processes and psychosis. Although there are several known sigma receptor types, only the type I receptor (sigma 1) has been cloned. To uncover the in vivo relevance of sigma-receptors, we have generated knockout mice for sigma 1. Despite the broad expression pattern found for the sigma 1-gene, homozygous mutant mice are viable, fertile and do not display any overt phenotype, compared with their wild-type litter-mates, in mixed genetic backgrounds. However, a significant decrease in the hypermotility response has been measured in knockout mice upon challenge with (+)SKF-10 047, in agreement with the involvement of sigma 1-receptors in the induction of psychostimulant actions. The activity of sigma 2-receptors seems to be unaffected in sigma 1-mutant mice. These knockout mice could contribute to better understand the in vivo role of sigma-receptors.

Keratin 17 null mice exhibit age- and strain-dependent alopecia

Onset of type I keratin 17 (K17) synthesis marks the adoption of an appendageal fate within embryonic ectoderm, and its expression persists in specific cell types within mature hair, glands, and nail. We report that K17 null mice develop severe alopecia during the first week postbirth, correlating with hair fragility, alterations in follicular histology, and apoptosis in matrix cells. These alterations are incompletely penetrant and normalize starting with the first postnatal cycle. Absence of a hair phenotype correlates with a genetic strain-dependent compensation by related keratins, including K16. These findings reveal a crucial role for K17 in the structural integrity of the first hair produced and the survival of hair-producing cells. Given that identical inherited mutations in this gene can cause either pachyonychia congenita or steatocystoma multiplex, the features of this mouse model suggest that this clinical heterogeneity arises from a cell type-specific, genetically determined compensation by related keratins.

Increased contribution of L-arginine-nitric oxide pathway in aorta of mice lacking the gene for vimentin

Experiments were designed to investigate endothelial function in the aorta of mice lacking the gene for the cytoskeleton protein vimentin (vim -/- ). Rings with and without endothelium from wild-type (vim +/+ ), heterozygous (vim +/- ), and homozygous (vim -/- ) mice were suspended in organ chambers to record of changes in isometric tension. During phenylephrine contraction, acetylcholine evoked comparable endothelium-dependent relaxations in the three groups. In the presence of Nomega-nitro-L-arginine, acetylcholine caused endothelium-dependent contractions, which were greater in vim -/- than in vim +/+ and vim +/- aortas. Indomethacin did not affect relaxation to acetylcholine in vim +/+ or in vim +/-, but it significantly increased the maximal response in vim -/- (67 +/- 7 vs. 102 +/- 4%). Response to acetylcholine in vim -/- aortas was not affected by cyclooxygenase type 2 inhibitor NS-398, the thromboxane receptor antagonist SQ-29,548, or superoxide dismutase. Relaxations to sodium nitroprusside were not different between vim +/+ and vim -/- mice and were not affected by cyclooxygenase inhibition. Cyclic guanosine monophosphate levels, which were increased to a comparable level by acetylcholine in vim +/+ and vim -/-, were augmented by indomethacin in vim -/- aortas but not in vim +/+ aortas. Expression of endothelial nitric oxide synthase was not different between vim +/+ and vim -/- preparations. These results suggest that despite comparable endothelium-dependent responses to acetylcholine, endothelial cells from vim -/- mice release a cyclooxygenase product that compensates the augmented contribution of nitric oxide.

C(60)-based triads with improved electron-acceptor properties: pyrazolylpyrazolino[60]fullerenes

A series of triad pyrazolylpyrazolino[60]fullerenes has been prepared in one pot from suitably functionalized hydrazones by 1,3-dipolar cycloaddition reactions under microwave irradiation. The electrochemical properties of the compounds obtained were investigated by cyclic voltammmetry, and they show better electron acceptor character than the parent C(60) in all cases. Fluorescence experiments and time-resolved transition spectroscopy indicate the existence of photoinduced charge-transfer processes with the C(60) triplet acting as the acceptor.

Healthy mice with an altered c-myc gene: role of the 3' untranslated region revisited

c-Myc is a protooncogene involved in the control of cellular proliferation, differentiation and apoptosis. Like many other early response genes, regulation of c-myc expression is mainly controlled at the level of mRNA stability. Multiple cis-acting destabilizing elements have been described that are located both in the protein-coding region and in the 3' untranslated region (3' UTR). However, it is not known when they function during development and whether they act as partly redundant or independent elements to regulate c-myc mRNA level of expression. To begin to address these questions, we created a series of c-myc alleles modified in the 3' UTR, using homologous recombination and the Cre/loxP system, and analysed the consequences of these modifications in ES cells and transgenic animals. We found that deletion of the complete 3' UTR, including runs of Us and AU-rich elements proposed, on the basis of cell-culture assays, to be involved in the control of c-myc mRNA stability, did not alter the steady-state level of c-myc mRNA in any of the various situations analysed in vivo. Moreover, mice homozygous for the 3' UTR-deleted gene were perfectly healthy and fertile. Our results therefore strongly suggest that the 3' UTR of c-myc mRNA does not play a major role in the developmental control of c-myc expression.

Synthesis and properties of isoxazolo[60]fullerene-donor dyads

A series of isoxazolo[60]fullerenes has been prepared in one pot from aldoximes under microwave irradiation. Several donors and acceptors were used as substituents. The absorption and emission spectra of these compounds in polar solvents suggest a weak charge-transfer interaction between the oxygen atom of the isoxazoline moiety and the C(60) cage, as well as a stronger interaction between the donor and the fullerene cage when the attached groups are p-N,N-dimethylaniline or ferrocene. The electrochemical properties of the compounds were investigated and they show the same or better acceptor character than C(60) in all cases. Theoretical calculations support the results obtained. Solvent effects in the (1)H NMR spectra have been determined and provide useful information concerning the polarization of dyads.

Teratocarcinomas induced by embryonic stem (ES) cells lacking vimentin: an approach to study the role of vimentin in tumorigenesis

Vimentin is a class III intermediate filament protein widely expressed in the developing embryo and in cells of mesenchymal origin in the adult. Vimentin knock-out mice develop and reproduce without any obvious defect. This is an unexpected finding in view of the high degree of conservation of the vimentin gene among vertebrates. However, it does not exclude the possibility of a role for vimentin in pathological conditions, like tumorigenesis. To address this question directly, we have used a teratocarcinoma model involving the injection of ES cells into syngeneic mice. ES cells lacking vimentin were generated from 129/Sv Vim-/- mice with high efficiency. The absence of vimentin did not affect ES cell morphology, viability or growth rate in vitro. Tumours were induced by subcutaneous injection of either Vim-/- or Vim+/+ ES cells into Vim+/+ and Vim-/- mice, in order to analyse the effect of the absence of vimentin in either the tumorigenic cells or the host mice. No significant differences were found in either tumour incidence, size or vascularization of teratocarcinomas obtained with all possible combinations. Vim-/- ES-derived tumours showed the same cellular composition typical of teratocarcinomas induced by wild-type ES cells together with a very similar apoptotic pattern. Taken together, these results demonstrate that in this model vimentin is not essential for efficient tumour growth and differentiation in vivo.

Comparative anatomy of the cerebellar cortex in mice lacking vimentin, GFAP, and both vimentin and GFAP

In the cerebellum of adult mammals, glial fibrillary acidic protein (GFAP) and vimentin (VIM) are coexpressed in Golgi epithelial cells (GEC), also known as Bergmann glia. In this study we used three transgenic knockout mice (GFAP, VIM and double GFAP and VIM) to analyze the involvement of these proteins in the building of glial filaments and in neuron-glia interactions. The cerebella of VIM, GFAP, and GFAP/VIM mutant mice were processed by the rapid Golgi method and also for electron microscopy. In VIM mutant mice, Bergmann fibers are hypertrophic with thickened appendages. In the electron microscope they appear as large glial profiles devoid of glial filaments, with embedded dendritic thorns and parallel fiber boutons. In addition, signs of degeneration are observed in Purkinje cells. In GFAP mutant mice, GEC exhibit fine, delicate processes, as those seen in wild-type animals, however, a large accumulation of lamellae and granular appendages was observed along their surfaces, which came into contact with each other. The electron microscope exhibited fine and scarce astroglial profiles containing some glial filaments, a stunted glia limitans, and the presence of large extracellular spaces. In double mutant mice, the two phenotypes are expressed but appear attenuated, with a total absence of glial filaments and the general appearance of immaturity for GEC. In conclusion, it appears that the absence of each of the proteins yields a specific phenotype and that the defects are not necessarily additive.

Impaired mechanical stability, migration and contractile capacity in vimentin-deficient fibroblasts

Loss of a vimentin network due to gene disruption created viable mice that did not differ overtly from wild-type littermates. Here, primary fibroblasts derived from vimentin-deficient (-/-) and wild-type (+/+) mouse embryos were cultured, and biological functions were studied in in vitro systems resembling stress situations. Stiffness of -/- fibroblasts was reduced by 40% in comparison to wild-type cells. Vimentin-deficient cells also displayed reduced mechanical stability, motility and directional migration towards different chemo-attractive stimuli. Reorganization of collagen fibrils and contraction of collagen lattices were severely impaired. The spatial organization of focal contact proteins, as well as actin microfilament organization was disturbed. Thus, absence of a vimentin filament network does not impair basic cellular functions needed for growth in culture, but cells are mechanically less stable, and we propose that therefore they are impaired in all functions depending upon mechanical stability.

Retention of the fetoacinar pancreatic (FAP) protein to the endoplasmic reticulum of tumor cells

The fetoacinar pancreatic (FAP) protein is a specific component of the human exocrine pancreas associated with the differentiation and proliferation of acinar cells. FAP expression is enhanced in cases of pancreatic exocrine cancer and it is found in relatively high concentrations in pathological pancreatic juices. However, tumor cell lines do not secrete FAP into the culture medium. In this paper we analyze the intracellular localization of FAP in cell lines and compare some biological properties of the tumoral FAP with the normal adult and fetal forms. Immunocytological experiments performed using Mab J28 which characterizes FAP, gave a staining pattern suggestive of FAP localization in the ER. Subcellular fractionation corroborated this localization and established that FAP is tightly associated with the microsomal membranes. The absence of reactivity of the tumoral FAP with wheat germ agglutinin lectin and its strong reactivity with concanavalin A is consistent with the idea that FAP in tumor cells does not reach the Golgi apparatus and it is consequently retained in the endoplasmic reticulum (ER). FAP contained in hepatic metastasis derived from pancreatic adenocarcinoma appeared to be similar, if not identical, to that expressed by cell lines. This supports the hypothesis that FAP retention in the ER of malignant cells is a physiological phenomenon and not the result of a modification of cell lines due to the culture conditions. FAP expressed by cancer cell lines and metastases appeared by sodium dodecyl sulfate polyacrylamide gel electrophoresis a homogeneous protein with a M(r) of 120,000. Instead, the secreted mature protein consists of a main component of M(r) 110,000 and shows pronounced polymorphism (dispersion from M(r) 110,000 to 80,000). Increased size of the ER-retained protein is likely due to elongation of the peptide chain. Defective processing in the ER as a result of amino acid mutation could therefore explain the behavior of this protein in tumors.