Biology subjects

Colonna, M.

Publications and source records attributed to Colonna, M..

27 records · Page 2Linked to original sources

bioRxiv2022

Plasmacytoid dendritic cells regulate megakaryocyte and platelet homeostasis

Platelet homeostasis is essential for vascular integrity and immune defense. While the process of platelet formation by fragmenting megakaryocytes (thrombopoiesis) has been extensively studied, the cellular and molecular mechanisms required to constantly replenish the pool of megakaryocytes by their progenitor cells (megakaryopoiesis) remains unclear. Here we use intravital 2 photon microscopy to track individual megakaryopoiesis over days. We identify plasmacytoid dendritic cells (pDCs) as crucial bone marrow niche cells that regulate megakaryopoiesis. pDCs monitor the bone marrow for platelet-producing megakaryocytes and deliver IFN- to the megakaryocytic niche to trigger local on-demand proliferation of megakaryocyte progenitors. This fine-tuned coordination between thrombopoiesis and megakaryopoiesis is crucial for megakaryocyte and platelet homeostasis in steady state and stress. However, uncontrolled pDC function within the megakaryocytic niche is detrimental. Accordingly, we show that pDCs activated by SARS-CoV2 drive inappropriate megakaryopoiesis associated with thrombotic complications. Together, we uncover a hitherto unknown megakaryocytic bone marrow niche maintained by the constitutive delivery of pDC-derived IFN-.

immunology↗

bioRxiv2022

The Transcription Factor Bach2 Negatively Regulates Natural Killer Cell Maturation and Function

BTB domain And CNC Homolog 2 (Bach2) is a transcription repressor that actively participates in T and B lymphocyte development, but it is unknown if Bach2 is also involved in the development of innate immune cells, such as natural killer (NK) cells. Here, we followed the expression of Bach2 during NK cell development, finding that it peaked in CD27+CD11b+ cells and decreased upon further maturation. Bach2 expression positively correlated with that of the transcription factor TCF1 and negatively correlated with genes encoding NK effector molecules as well as genes involved in the cell cycle. Bach2-deficient mice showed increased numbers of terminally differentiated NK cells with increased production of granzymes and cytokines. NK cell-mediated control of tumor metastasis was also augmented in the absence of Bach2. Therefore, Bach2 is a key checkpoint protein regulating NK terminal maturation.

immunology↗

bioRxiv2022

IL-34 deficiency impairs FOXP3+ Treg function and increases susceptibility to autoimmunity

Immune homeostasis requires fully functional Tregs with a stable phenotype to control autoimmunity. Although IL-34 is a cytokine first described as mainly involved in monocyte cell survival and differentiation, we recently described its expression by CD8+ Tregs in a rat model of transplantation tolerance and by activated FOXP3+ CD4+ and CD8+ Tregs in human healthy individuals. However, its role in autoimmunity and potential in human diseases remain to be determined. Here we report that the absence of expression of IL-34 in Il34-/- rodents leads to an unstable phenotype, with production of multiple auto-antibodies, exacerbated under inflammatory conditions with increased susceptibility to DSS- and TNBS-colitis in deficient animals. Moreover, we strikingly revealed the inability of Il34-/- CD4+ Tregs to protect Il2rg-/- rats from a wasting disease induced by transfer of pathogenic cells, in contrast to Il34+/+ CD4+ Tregs. We also showed that IL-34 treatment delayed EAE in mice as well as GVHD and human skin allograft rejection in immune humanized immunodeficient NSG mice. Finally, we show that presence of IL-34 in the serum is associated with a longer rejection-free period in kidney transplanted patients. Altogether, our data emphasize on the crucial necessity of IL-34 for immune homeostasis and for CD4+ Tregs suppressive function. Our data also shows the therapeutic potential of IL-34 in human transplantation and auto-immunity.

immunology↗

bioRxiv2021

Surveillance of Shiga toxin-producing Escherichia coli associated bloody diarrhea in Argentina

In Argentina, the hemolytic uremic syndrome associated with Shiga toxin-producing Escherichia coli (STEC-HUS) infection is endemic, and reliable data about prevalence and risk factors are available since 2000. However, information about STEC-associated bloody diarrhea (BD) cases is limited. A prospective study was carried out in seven tertiary-hospitals and 18 Referral Units from different regions, aiming to determine (i) STEC-positive BD cases frequency in 714 children aged 1 to 9 years old; and (ii) rate of progression to HUS. The number and regional distribution of STEC-HUS cases assisted in the same hospitals and period was also assessed. A total of 29 (4.1%) STEC-positive BD cases were confirmed by Shiga Toxin Quik Chek (STQC) and/or mPCR. The highest frequencies were found in the Southern region (Neuquen, 8.7%; Bahia Blanca, 7.9%), in children between 12 and 23 month of age (8.8%), during summertime. Four (13.8%) cases progressed to HUS, three to five days after BD onset. Twenty-seven STEC-HUS children mainly under 5 years old (77.8%) were enrolled, 51.9% were female; 44% were Stx-positive by STQC and all by mPCR. The most common serotypes were O157:H7 and O145:H28 and prevalent genotypes were stx2a-only or associated, both among BD and HUS cases. Considering the endemic behavior of HUS and its impact on public health, it is important to have updated information about the epidemiology of the diarrheal disease for early recognition of infected patients and initiation of supportive treatment. Finally, it also gives the opportunity to respond to outbreak situations effectively and in timely manner.

microbiology↗

bioRxiv2020

A novel redox-active switch in Fructosamine-3-kinases expands the regulatory repertoire of the protein kinase superfamily

Aberrant regulation of metabolic kinases by altered redox homeostasis is a major contributing factor in aging and disease such as diabetes. However, the biochemical mechanisms by which metabolic kinases are regulated under oxidative stress is poorly understood. In this study, we demonstrate that the catalytic activity of a conserved family of Fructosamine-3-kinases (FN3Ks), which are evolutionarily related to eukaryotic protein kinases (ePKs), are regulated by redox-active cysteines in the kinase domain. By solving the crystal structure of FN3K homolog from Arabidopsis thaliana (AtFN3K), we demonstrate that it forms an unexpected strand-exchange dimer in which the ATP binding P-loop and adjoining beta strands are swapped between two chains in the dimer. This dimeric configuration is characterized by strained inter-chain disulfide bonds that stabilize the P-loop in an extended conformation. Mutational analysis and solution studies confirm that the strained disulfides function as redox "switches" to reversibly regulate FN3K activity and dimerization. Consistently, we find that human FN3K (HsFN3K), which contains an equivalent P-loop Cys, is also redox-sensitive, whereas ancestral bacterial FN3K homologs, which lack a P-loop Cys, are not. Furthermore, CRISPR knockout of FN3K in human HepG2 cells results in significant upregulation of redox metabolites including glutathione. We propose that redox regulation evolved progressively in FN3Ks in response to changing cellular redox conditions. Our studies provide important new insights into the origin and evolution of redox regulation in the protein kinase superfamily and open new avenues for targeting HsFN3K in diabetic complications.

biochemistry↗

bioRxiv2019

Peripheral nerve resident macrophages are microglia-like cells with tissue-specific programming

Whereas microglia are recognized as fundamental players in central nervous system (CNS) development and function, much less is known about macrophages of the peripheral nervous system (PNS). Here we show that self-maintaining PNS macrophages share unique features with CNS microglia. By comparing gene expression across neural and conventional tissue-resident macrophages, we identified transcripts that were shared among neural resident macrophages as well as selectively enriched in PNS macrophages. Remarkably, PNS macrophages constitutively expressed genes previously identified to be upregulated by activated microglia during aging or neurodegeneration. Several microglial activation-associated and PNS macrophage-enriched genes were also expressed in spinal cord microglia at steady state. While PNS macrophages arose from both embryonic and hematopoietic precursors, their expression of activation-associated genes did not differ by ontogeny. Collectively, these data uncover shared and unique features between neural resident macrophages and emphasize the role of nerve environment for shaping PNS macrophage identity.

immunology↗

bioRxiv2019

Microglia control small vessel calcification via TREM2

Microglia participate in CNS development and homeostasis and are often implicated in modulating disease processes in the CNS. However, less is known about the role of microglia in the biology of the neurovascular unit (NVU). In particular, data are scant on whether microglia are involved in CNS vascular pathology. In this study, we use a mouse model of primary familial brain calcification (PFBC) - Pdgfbret/ret to investigate the role of microglia in calcification of the NVU. We report that microglia enclosing vessel-calcifications, coined calcification-associated microglia (CAM), display a distinct activation signature. Pharmacological ablation of microglia with the CSF1R inhibitor - PLX5622 leads to aggravated vessel calcification. Additionally, depletion of microglia in wild-type and Pdgfbret/ret mice causes the development of bone protein (osteocalcin, osteopontin) containing axonal spheroids in the white matter. Mechanistically, we show that microglia require functional TREM2 for controlling vessel-associated calcification. In conclusion, our results demonstrate that microglial activity in the setting of pathological vascular calcification is beneficial. In addition, we identify a new, previously unrecognized function of microglia in halting the expansion of ectopic calcification.

neuroscience↗

bioRxiv2019

Toxoplasma gondii infection drives conversion of NK Cells into ILC1s

Innate lymphoid cells (ILCs) were originally classified based on their cytokine profiles, placing natural killer (NK) cells and ILC1s together, but recent studies support their separation into different lineages at steady-state. However, tumors may induce NK cell conversion into ILC1-like cells that are limited to the tumor microenvironment and whether this conversion occurs beyond this environment remains unknown. Here we describe Toxoplasma gondii infection converts NK cells into cells resembling steady-state ILC1s that are heterogeneous and distinct from both steady-state NK cells and ILC1s in uninfected mice. Most toxoplasma-induced ILC1s were Eomes-dependent, indicating that NK cells can give rise to Eomes- Tbet-dependent ILC1-like cells that circulate widely and persist independent of ongoing infection. Moreover, these changes appear permanent, as supported by epigenetic analyses. Thus, these studies markedly expand current concepts of NK cells, ILCs, and their potential conversion.

immunology↗

bioRxiv2018

High affinity interactions and signal transduction between Aβ oligomers and TREM2

Rare coding variant in the Triggering receptor expressed on myeloid cells 2 (TREM2) are associated with increased risk for Alzheimers disease (AD), but how they confer this risk remains uncertain. We assessed binding of TREM2, AD associated TREM2 variants to various forms of A{beta} and APOE in multiple assays. TREM2 interacts directly with various forms of A{beta}, with highest affinity interactions observed between TREM2 and soluble A{beta}42 oligomers. We confirm the previous interaction between APOE3 and APOE4 and TREM2. High affinity binding of TREM2 to A{beta} oligomers is characterized by very slow dissociation. Pre-incubation with A{beta} is shown to block the interaction of APOE. In cellular assays, AD-associated variants of TREM2 reduced the amount of A{beta}42 internalized, and in NFAT assay the R47H variant decreased NFAT signaling activity in response to A{beta}42. These studies demonstrate i) a high affinity interaction between TREM2 and A{beta} oligomers that can block interaction with another ligand and ii) that AD-associated TREM2 variants bind A{beta} with equivalent affinity but show loss of function in terms of signaling and A{beta} internalization.

cell biology↗