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1. Lophomonas as a respiratory pathogen—jumping the gun

   https://doi.org/10.1128/jcm.00845-23  

   Mewara, Abhishek; Gile, Gillian H; Mathison, Blaine; Zhao, Huan; Pritt, Bobbi; Bradbury, Richard S (January 2024, Journal of Clinical Microbiology)

   Humphries, Romney M (Ed.)

   ABSTRACT Human infections with the protozoanLophomonashave been increasingly reported in the medical literature over the past three decades. Initial reports were based on microscopic identification of the purported pathogen in respiratory specimens. Later, a polymerase chain reaction (PCR) was developed to detectLophomonas blattarum, following which there has been a significant increase in reports. In this minireview, we thoroughly examine the published reports ofLophomonasinfection to evaluate its potential role as a human pathogen. We examined the published images and videos of purportedLophomonas,compared its morphology and motility characteristics with host bronchial ciliated epithelial cells and trueL. blattarumderived from cockroaches, analyzed the published PCR that is being used for its diagnosis, and reviewed the clinical data of patients reported in the English and Chinese literature. From our analysis, we conclude that the images and videos from human specimens do not represent trueLophomonasand are predominantly misidentified ciliated epithelial cells. Additionally, we note that there is insufficient clinical evidence to attribute the cases toLophomonasinfection, as the clinical manifestations are non-specific, possibly caused by other infections and comorbidities, and there is no associated tissue pathology attributable toLophomonas. Finally, our analysis reveals that the published PCR is not specific toLophomonasand can amplify DNA from commensal trichomonads. Based on this thorough review, we emphasize the need for rigorous scientific scrutiny before a microorganism is acknowledged as a novel human pathogen and discuss the potential harms of misdiagnoses for patient care and scientific literature. 

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2. Key Roles of CACNA1C /Cav1.2 and CALB1/Calbindin in Prefrontal Neurons Altered in Cognitive Disorders

   https://doi.org/10.1001/jamapsychiatry.2024.1112  

   Datta, Dibyadeep; Yang, Shengtao; Joyce, Mary_Kate P; Woo, Elizabeth; McCarroll, Steven A; Gonzalez-Burgos, Guillermo; Perone, Isabella; Uchendu, Stacy; Ling, Emi; Goldman, Melissa; et al (May 2024, JAMA Psychiatry)

   ImportanceThe risk of mental disorders is consistently associated with variants inCACNA1C(L-type calcium channel Cav1.2) but it is not known why these channels are critical to cognition, and whether they affect the layer III pyramidal cells in the dorsolateral prefrontal cortex that are especially vulnerable in cognitive disorders. ObjectiveTo examine the molecular mechanisms expressed in layer III pyramidal cells in primate dorsolateral prefrontal cortices. Design, Setting, and ParticipantsThe design included transcriptomic analyses from human and macaque dorsolateral prefrontal cortex, and connectivity, protein expression, physiology, and cognitive behavior in macaques. The research was performed in academic laboratories at Yale, Harvard, Princeton, and the University of Pittsburgh. As dorsolateral prefrontal cortex only exists in primates, the work evaluated humans and macaques. Main Outcomes and MeasuresOutcome measures included transcriptomic signatures of human and macaque pyramidal cells, protein expression and interactions in layer III macaque pyramidal cells using light and electron microscopy, changes in neuronal firing during spatial working memory, and working memory performance following pharmacological treatments. ResultsLayer III pyramidal cells in dorsolateral prefrontal cortex coexpress a constellation of calcium-related proteins, delineated byCALB1(calbindin), and high levels ofCACNA1C(Cav1.2),GRIN2B(NMDA receptor GluN2B), andKCNN3(SK3 potassium channel), concentrated in dendritic spines near the calcium-storing smooth endoplasmic reticulum. L-type calcium channels influenced neuronal firing needed for working memory, where either blockade or increased drive by β1-adrenoceptors, reduced neuronal firing by a mean (SD) 37.3% (5.5%) or 40% (6.3%), respectively, the latter via SK potassium channel opening. An L-type calcium channel blocker or β1-adrenoceptor antagonist protected working memory from stress. Conclusions and RelevanceThe layer III pyramidal cells in the dorsolateral prefrontal cortex especially vulnerable in cognitive disorders differentially express calbindin and a constellation of calcium-related proteins including L-type calcium channels Cav1.2 (CACNA1C), GluN2B-NMDA receptors (GRIN2B), and SK3 potassium channels (KCNN3), which influence memory-related neuronal firing. The finding that either inadequate or excessive L-type calcium channel activation reduced neuronal firing explains why either loss- or gain-of-function variants inCACNA1Cwere associated with increased risk of cognitive disorders. The selective expression of calbindin in these pyramidal cells highlights the importance of regulatory mechanisms in neurons with high calcium signaling, consistent with Alzheimer tau pathology emerging when calbindin is lost with age and/or inflammation. 

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3. A high-resolution view of the immune and stromal cell response to Haemophilus ducreyi infection in human volunteers

   https://doi.org/10.1128/mbio.03885-24  

   Brothwell, Julie A; Wei, Yuhui; Wang, Jia; Guo, Tingbo; Zhang, Chi; Fortney, Kate R; Duplantier, Rory; Chen, Li; Batteiger, Teresa A; Kaplan, Mark H; et al (March 2025, mBio)

   Blaser, Martin J (Ed.)

   ABSTRACT Haemophilus ducreyicauses the genital ulcer disease chancroid and cutaneous ulcers in children. To study its pathogenesis, we developed a human challenge model in which we infect the skin on the upper arm of human volunteers withH. ducreyito the pustular stage of disease. The model has been used to define lesional architecture, describe the immune infiltrate into the infected sites using flow cytometry, and explore the molecular basis of the immune response using bulk RNA-seq. Here, we used single cell RNA-seq (scRNA-seq) and spatial transcriptomics to simultaneously characterize multiple cell types within infected human skin and determine the cellular origin of differentially expressed transcripts that we had previously identified by bulk RNA-seq. We obtained paired biopsies of pustules and wounded (mock infected) sites from five volunteers for scRNA-seq. We identified 13 major cell types, including T- and NK-like cells, macrophages, dendritic cells, as well as other cell types typically found in the skin. Immune cell types were enriched in pustules, and some subtypes within the major cell types were exclusive to pustules. Sufficient tissue specimens for spatial transcriptomics were available from four of the volunteers. T- and NK-like cells were highly associated with multiple antigen presentation cell types. In pustules, type I interferon stimulation was high in areas that were high in antigen presentation—especially in macrophages near the abscess—compared to wounds. Together, our data provide a high-resolution view of the cellular immune response to the infection of the skin with a human pathogen.IMPORTANCEA high-resolution view of the immune infiltrate due to infection with an extracellular bacterial pathogen in human skin has not yet been defined. Here, we used the human skin pathogenHaemophilus ducreyiin a human challenge model to identify on a single cell level the types of cells that are present in volunteers who fail to spontaneously clear infection and form pustules. We identified 13 major cell types. Immune cells and immune-activated stromal cells were enriched in pustules compared to wounded (mock infected) sites. Pustules formed despite the expression of multiple pro-inflammatory cytokines, such as IL-1β and type I interferon. Interferon stimulation was most evident in macrophages, which were proximal to the abscess. The pro-inflammatory response within the pustule may be tempered by regulatory T cells and cells that express indoleamine 2,3-dioxygenase, leading to failure of the immune system to clearH. ducreyi. 

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4. Glycerophosphocholine provision rescues Candida albicans growth and signaling phenotypes associated with phosphate limitation

   https://doi.org/10.1128/msphere.00231-23  

   King, William R.; Acosta-Zaldívar, Maikel; Qi, Wanjun; Cherico, Nicholas; Cooke, Lauren; Köhler, Julia R.; Patton-Vogt, Jana (December 2023, mSphere)

   Lorenz, Michael (Ed.)

   ABSTRACT The fungal pathogenCandida albicansmust acquire phosphate to colonize, infect, and proliferate in the human host.C. albicanshas four inorganic phosphate (P_i) transporters, Pho84 being the major high-affinity transporter; its cells can also use glycerophosphocholine (GPC) as their sole phosphate source. GPC is a lipid metabolite derived from deacylation of the lipid phosphatidylcholine. GPC is found in multiple human tissues, including the renal medulla, where it acts as an osmolyte.C. albicansimports GPC into the cell via the Git3 and Git4 transporters. Internalized GPC can be hydrolyzed to release P_i. To determine if GPC import and subsequent metabolism affect phosphate homeostasis upon P_ilimitation, we monitored growth and phenotypic outputs in cells provided with either P_ior GPC. Inpho84∆/∆ mutant cells that exhibit phenotypes associated with P_ilimitation, GPC provision rescued sensitivity to osmotic and cell wall stresses. The glycerophosphodiesterase Gde1 was required for phenotypic rescue of osmotic stress by GPC provision. GPC provision, like P_iprovision, resulted in repression of the PHO regulon and activation of TORC1 signaling. P_iuptake was similar to GPC uptake when phosphate availability was low (200 µM). While available at lower concentrations than P_iin the human host, GPC is an advantageous P_isource for the fungus because it simultaneously serves as a choline source. In summary, we find GPC is capable of substituting for P_iinC. albicansby many though not all criteria and may contribute to phosphate availability for the fungus in the human host. IMPORTANCECandida albicansis the most commonly isolated species from patients suffering from invasive fungal disease.C. albicansis most commonly a commensal organism colonizing a variety of niches in the human host. The fungus must compete for resources with the host flora to acquire essential nutrients such as phosphate. Phosphate acquisition and homeostasis have been shown to play a key role inC. albicansvirulence, with several genes involved in these processes being required for normal virulence and several being upregulated during infection. In addition to inorganic phosphate (P_i),C. albicanscan utilize the lipid-derived metabolite glycerophosphocholine (GPC) as a phosphate source. As GPC is available within the human host, we examined the role of GPC in phosphate homeostasis inC. albicans. We find that GPC can substitute for P_iby many though not all criteria and is likely a relevant physiological phosphate source forC. albicans. 

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5. Altering metabolite distribution at Xenopus cleavage stages affects left–right gene expression asymmetries

   https://doi.org/10.1002/dvg.23418  

   Onjiko, Rosemary M.; Nemes, Peter; Moody, Sally A. (April 2021, genesis)

   Summary The left–right (L–R) axis of most bilateral animals is established during gastrulation when a transient ciliated structure creates a directional flow of signaling molecules that establish asymmetric gene expression in the lateral plate mesoderm. However, in some animals, an earlier differential distribution of molecules and cell division patterns initiate or at least influence L–R patterning. Using single‐cell high‐resolution mass spectrometry, we previously reported a limited number of small molecule (metabolite) concentration differences between left and right dorsal‐animal blastomeres of the eight‐cellXenopusembryo. Herein, we examined whether altering the distribution of some of these molecules influenced early events in L–R patterning. Using lineage tracing, we found that injecting right‐enriched metabolites into the left cell caused its descendant cells to disperse in patterns that varied from those in control gastrulae; this did not occur when left‐enriched metabolites were injected into the right cell. At later stages, injecting left‐enriched metabolites into the right cell perturbed the expression of genes known to: (a) be required for the formation of the gastrocoel roof plate (foxj1); (b) lead to the asymmetric expression of Nodal (dand5/coco); or (c) result from asymmetricalnodalexpression (pitx2). Despite these perturbations in gene expression, we did not observe heterotaxy in heart or gut looping at tadpole stages. These studies indicate that altering metabolite distribution at cleavage stages at the concentrations tested in this study impacts the earliest steps of L–R gene expression that then can be compensated for during organogenesis. 

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