Biology subjects

Fernandez, M.

Publications and source records attributed to Fernandez, M..

46 records · Page 3Linked to original sources

bioRxiv2021

Intercellular crosstalk regulating ARRB2/RARRES1 is involved in transition from fibrosis to cancer

Progressive fibrogenesis in chronic liver injury is often associated with cancer development. Beta-arrestin-2 (ARRB2) is a regulator of the profibrotic Angiotensin II type 1 receptor (AGTR1). The role of ARRB2 in liver fibrosis and in the transition from fibrosis to cancer is not fully understood and was investigated in this study. This study demonstrates that upregulation of the retinoic acid receptor responder 1 (RARRES1) in HSC mediated by ARRB2 leads to fibrosis. This process is driven by exosomal ARRB2 transfer to HSC, major fibrosis contributors, from injured hepatocytes, which highly express ARRB2. By contrast, downregulation of RARRES1 in hepatocytes induces malignant transformation and hepatocellular carcinoma (HCC) development. Consequently, Arrb2-deficient mice show higher number and size of liver tumors than wild-type mice in a hepatocellular carcinoma model with fibrosis. The identified relationship between ARRB2 and RARRES1 was observed in at least two species, including human cells and tissues in fibrosis and HCC and has a predictive value for survival in cancer patients. This study describes the discovery of a novel molecular pathway mediating the transition from fibrosis to cancer offering potential diagnostics and therapeutics.

molecular biology↗

bioRxiv2021

Altered cerebellar response to somatosensory stimuli in the Cntnap2 mouse model of autism

Atypical sensory processing is currently included within the diagnostic criteria of autism. The cerebellum is known to integrate sensory inputs of different modalities through its connectivity to the cerebral cortex. Interestingly, cerebellar malformations are among the most replicated features found in postmortem brain of individuals with autism. We studied cerebellar integration of sensory information in a mouse model of autism, knockout for the Cntnap2 gene. Cntnap2 is widely expressed in Purkinje cells and has been recently reported to regulate their morphology. Further, individuals with CNTNAP2 mutations display cerebellar malformations and CNTNAP2 antibodies are associated with a mild form of cerebellar ataxia. Previous studies in the Cntnap2 mouse model show an altered cerebellar sensory learning. However, a physiological analysis of cerebellar function has not been performed yet. We studied sensory evoked potentials in cerebellar Crus I/II region upon electrical stimulation of the whisker pad in alert mice and found striking differences between WT and Cntnap2 KO mice. In addition, single-cell recordings identified alterations in both sensory-evoked and spontaneous firing patterns of Purkinje cells. These changes were accompanied by altered intrinsic properties and morphological features of these neurons. Together, these results indicate that the Cntnap2 mouse model could provide novel insight into the pathophysiological mechanisms of ASD core sensory deficits.

neuroscience↗

bioRxiv2020

Transcriptional and immunological analysis of the putative outer membrane protein and vaccine candidate TprL of Treponema pallidum

BackgroundAn effective syphilis vaccine should elicit antibodies to Treponema pallidum subsp. pallidum (T. p. pallidum) surface antigens to induce pathogen clearance through opsonophagocytosis. Although the combination of bioinformatics, structural, and functional analyses of T. p. pallidum genes to identify putative outer membrane proteins (OMPs) resulted in a list of potential vaccine candidates, still very little is known about whether and how transcription of these genes is regulated during infection. This knowledge gap is a limitation to vaccine design, as immunity generated to an antigen that can be down-regulated or even silenced at the transcriptional level without affecting virulence would not induce clearance of the pathogen, hence allowing disease progression. Principal findingsWe report here that tp1031, the T. p. pallidum gene encoding the putative OMP and vaccine candidate TprL is differentially expressed in several T. p. pallidum strains, suggesting transcriptional regulation. Experimental identification of the tprL transcriptional start site revealed that a homopolymeric G sequence of varying length resides within the tprL promoter and that its length affects promoter activity compatible with phase variation. Conversely, in the closely related pathogen T. p. subsp. pertenue, the agent of yaws, where a naturally-occurring deletion has eliminated the tprL promoter region, elements necessary for protein synthesis, and part of the gene ORF, tprL transcription level are negligible compared to T. p. pallidum strains. Accordingly, the humoral response to TprL is absent in yaws-infected laboratory animals and patients compared to syphilis-infected subjects. ConclusionThe ability of T. p. pallidum to stochastically vary tprL expression should be considered in any vaccine development effort that includes this antigen. The role of phase variation in contributing to T. p. pallidum antigenic diversity should be further studied. Author SummarySyphilis is still an endemic disease in many low- and middle-income countries and has been resurgent in high-income nations for almost two decades now. In endemic areas, syphilis still causes significant morbidity and mortality in patients, particularly when its causative agent, the bacterium Treponema pallidum subsp. pallidum is transmitted to the fetus during pregnancy. Although there are significant ongoing efforts to identify an effective syphilis vaccine to bring into clinical trials within the decade in the U.S., such efforts are partially hindered by the lack of knowledge on transcriptional regulation of many genes encoding vaccine candidates. Here, we start addressing this knowledge gap for the putative outer membrane protein (OMP) and vaccine candidates TprL, encoded by the tp1031 gene. As we previously reported for other putative OMP-encoding genes of the syphilis agent, tprL transcription level appears to be affected by the length of a homopolymeric sequence of guanosines (Gs) located within the gene promoter. This is a mechanism known as phase variation and often involved in altering the surface antigenic profile of a bacterial pathogen to facilitate immune evasion and/or adaptation to the host milieu.

microbiology↗

bioRxiv2020

GxGxE interactions and adaptive potential of the microbiome in Drosophila melanogaster

Can the microbiome serve as a reservoir of adaptive potential for hosts? To address this question, we leveraged [~]150 generations of experimental evolution in Drosophila melanogaster in a stressful, high-sugar (HS) diet. We performed a fully reciprocal transplant experiment using the control and evolved HS bacteria. If the microbiome confers benefits to hosts, then transplant recipients should gain fitness benefits compared to controls. Interestingly, we found that benefits do exist, but mismatches between fly evolution and microbiome exerted fitness costs by slowing development and reducing fecundity, especially in the stressful HS diet. The dominant HS bacteria (Acetobacter pasteurianus) uniquely encoded several genes to enable uric acid degradation, mediating the toxic effects of uric acid accumulation due to the HS diet for flies. Our study demonstrates that host genotype x microbiome x environment interactions have substantial effects on host phenotype, highlighting how host evolution and ecological context together shape the adaptive potential of the microbiome.

evolutionary biology↗

bioRxiv2020

BATF3-dependent induction of IL-27 by B cells bridges the innate and adaptive stages of the antibody response

B cells are exposed to innate and T cell stimuli during the antibody response, although whether and how they functionally integrate such signals are unclear. Here we have identified IL-27 as the cytokine specifically produced by murine B cells upon sequential stimulation by TLR ligands and then CD154 and IL-21, the hallmark factors of T follicular helper cells, and during the T-dependent antibody response to a conjugated hapten or virus infection. B-cell Il27p28 transcription is concomitant with increased locus accessibility and depends on newly induced BATF3 transcription factor. IL-27-producing B cells are inefficient in antibody secretion, but cooperate with IFN{gamma} to promote proliferation, survival, class-switching and plasma cell differentiation of CD40-activated B cells, leading to optimal IgG2a and IgG1 responses. Overall, IL-27-producing B cells function as "helper" B cells that integrate the innate and adaptive stages of the antibody response. One-sentence summaryB cells integrate innate TLR and adaptive CD40 signals to induce BATF3 transcription factor for production of IL-27, which together with INFg optimizes antibody responses.

immunology↗

bioRxiv2019

CD4+ T cells from chronic Chagas disease patients with different degrees of cardiac compromise exhibit distinct expression patterns of inhibitory receptors TIGIT, Tim-3 and Lag-3.

T cells are central to adaptive immune response against T. cruzi infection. In the chronic stage of Chagas disease, circulating parasite-specific memory T cells show reduced functionality and increased expression of inhibitory receptors, possibly as a result of persistent antigenic stimulation. This exhausted phenotype has been linked to progression of cardiac pathology while, contrariwise, the presence of polyfunctional T cells shows association with therapeutic success and more efficient control of infection. Given this, we hypothesized that inhibitory receptors TIGIT, Tim-3 and Lag-3 may be involved in immune modulation of anti-T. cruzi T cell response, and therefore may play a role in the containment or the unleashing of inflammatory phenomena that ultimately lead to tissue damage and pathology. In this preliminary study, we assess the frequency of CD4+ T cells expressing each of these receptors and their relation to cellular activation. Samples from chronic Chagas disease patients with different degrees of cardiac compromise, and non-infected donors were analyzed under different stimulation conditions. Our results show that the frequency of TIGIT+ CD4+ T cells is increased in Chagas patients, while Tim-3+ cells are more abundant in patients with signs of cardiac alterations. In addition, the frequency of Lag-3+ cells increases in non-activated CD4+ T cells from Chagas patients without demonstrable cardiopathy upon pathogen-specific in vitro antigenic stimulation.

immunology↗

bioRxiv2019

Altered frequency of CD24highCD38high transitional B cells in patients with cardiac involvement of chronic Chagas disease.

The cardiomyopathy developed by patients with chronic Chagas disease (CCD), one of the most severe consequences of T. cruzi infection, is mainly associated with an imbalance between an excessive inflammatory reaction and a defective immunomodulatory profile cause by host-parasite interaction. Despite the growing importance of the regulatory function of B-cells in many malignancies, few studies have addressed their immunosuppressive role in chronic Chagas disease. In this work, we tackled this issue by studying the proportion of different B cell subpopulations and their capacity to secrete IL-10 in individuals with distinct clinical forms of CCD. Seven-colour flow cytometry was performed to examine the peripheral blood B cell compartment in chronic Chagas disease (CCD) patients with and without cardiac manifestations (n=10 for each group) and non-infected donors (n=9). Peripheral blood mononuclear cells (PBMC) were incubated for 5h with PMA, ionomicyn and brefeldin A. According to the expression of markers CD19, CD24 and CD38, we showed an expansion of total B cell and transitional CD24highCD38high B cell subsets in CCD patients with cardiac involvement compared to non-infected donors. Furthermore, although no differences were observed in the frequency of total IL-10 producing B cells (B10) among the groups, CCD patients with cardiac involvement showed a statistically significant increased proportion of naive B10 cells and a tendency to an increased frequency of transitional B10 cells compared to non-infected donors. These findings suggest that immature transitional CD24highCD38high B cells are greatly expanded in patients with the cardiac form of chronic Chagas disease and these cells retain their ability to secrete IL-10 compared to non-infected donors. Furthermore, the distribution of naive, transitional and memory B cells inside the B10 cells followed the same pattern in chronic patients without cardiac involvement and non-infected individuals. Our work provides insight into the phenotypic distribution of regulatory B cell in CCD, an important step towards new strategies to prevent cardiomiopathy associated with T. cruzi infection.

immunology↗

bioRxiv2018

Fluctuating pathogen-mediated selection drives the maintenance of innate immune gene polymorphism in a widespread wild ungulate

Toll-like Receptors (TLR) play a central role in recognition and host frontline defence against a wide range of pathogens. A number of recent studies have shown that TLR genes (Tlrs) often exhibit a large polymorphism in natural populations. Yet, there is little knowledge on how this polymorphism is maintained and how it influences disease susceptibility in the wild. In a previous work, we showed that some Tlrs exhibit similarly high levels of genetic diversity than Mhc and contemporary signatures of balancing selection in roe deer (Capreolus capreolus), an abundant and widespread ungulate in Europe. Here, we tested whether Mhc-Drb or Tlr (Tlr2, Tlr4 and Tlr5) diversity is driven by pathogen-mediated selection. We examined the relationships between their genotype (heterozygosity status and presence of specific alleles) and infections with Toxoplasma and Chlamydia, two intracellular pathogens known to cause reproductive failure in ungulates. We showed that Toxoplasma and Chlamydia exposures vary significantly across year and landscape structure with few co-infection events detected, and that the two pathogens act antagonistically on Tlr2 polymorphism. By contrast, we found no evidence of association with Mhc-Drb and a limited support for Tlr heterozygosity advantage. Our study confirmed the importance of looking beyond Mhc genes in wildlife immunogenetic studies. It also emphasized the necessity to consider multiple pathogen challenges and their spatiotemporal variation to improve our understanding of vertebrate defence evolution against pathogens.

evolutionary biology↗

bioRxiv2018

Finding the signal in the noise of Citizen Science Observations

While many observations of species are being collected by citizen science projects worldwide, it can be challenging to identify projects collecting data that effectively monitor biodiversity. Over the past several years the allure of taking a \"Big Data\" approach has provided the opportunity to gather massive quantities of observations via the Internet, too often with insufficient information to describe how the observations were made. Information about species populations -- where and when they occur and how many of them are there -- (i.e., the signal) can be lost because insufficient information is gathered to account for the inherent biases in data collection (i.e., the noise). Here we suggest that citizen science projects that have succeeded in motivating large numbers of participants, must consider factors that influence the ecological process that affect species populations as well as the observation process that determines how observations are made. Those citizen science projects that collect sufficient contextual information describing the observation process can be used to generate increasingly accurate information about the distribution and abundance of organisms. We illustrate this using eBird as a case study, describing how this citizen science platform is able to collect vital contextual information on the observation process while maintaining a broad global constituency of participants. We highlight how eBird provides information with which to generate biodiversity indicators -- specifically distribution, abundance, and habitat associations -- across the entire annual cycle, even for populations of long distance migratory birds, a highly challenging taxon.

ecology↗

bioRxiv2017

A common haplotype lowers SPI1 (PU.1) expression in myeloid cells and delays age at onset for Alzheimer’s disease

In this study we used age at onset of Alzheimers disease (AD), cerebrospinal fluid (CSF) biomarkers, and cis-expression quantitative trait loci (cis-eQTL) datasets to identify candidate causal genes and mechanisms underlying AD GWAS loci. In a genome-wide survival analysis of 40,255 samples, eight of the previously reported AD risk loci are significantly (P < 5x10-8) or suggestively (P < 1x10-5) associated with age at onset-defined survival (AAOS) and a further fourteen novel loci reached suggestive significance. Using stratified LD score regression we demonstrated a significant enrichment of AD heritability in hematopoietic cells of the myeloid and B-lymphoid lineage. We then investigated the impact of these 22 AAOS-associated variants on CSF biomarkers and gene expression in cells of the myeloid lineage. In particular, the minor allele of rs1057233 (G), within the previously reported CELF1 AD risk locus, shows association with higher age at onset of AD (P=8.40x10-6), higher CSF levels of A{beta}42 (P=1.2x10-4), and lower expression of SPI1 in monocytes (P=1.50x10-105) and macrophages (P=6.41x10-87). SPI1 encodes PU.1, a transcription factor critical for myeloid cell development and function. AD heritability is enriched within the SPI1 cistromes of monocytes and macrophages, implicating a myeloid PU.1 target gene network in the etiology of AD. Finally, experimentally altered PU.1 levels are correlated with phagocytic activity of BV2 mouse microglial cells and specific changes in the expression of multiple myeloid-expressed genes, including the mouse orthologs of AD-associated genes, APOE, CLU/APOJ, CD33, MS4A4A/MS4A6A, and TYROBP. Our results collectively suggest that lower SPI1 expression reduces AD risk by modulating myeloid cell gene expression and function.

neuroscience↗