Biology subjects

Hillman, H.

Publications and source records attributed to Hillman, H..

12 recordsLinked to original sources

bioRxiv2026

TREM2 encodes plaque macrophage plasticity to mediate atherosclerosis regression

Cholesterol lowering therapies stabilize atherosclerotic plaque and reduce ischemic events, but the molecular mechanisms governing plaque remodeling or regression remain poorly defined. The lipid sensor TREM2 is a key modulator of plaque-associated foam cell development and was upregulated by plaque macrophages in atherosclerosis regression. We examined macrophage- or monocyte-specific Trem2 deletion during regression in mice and found that TREM2 expression on plaque macrophages, not newly recruited monocytes, was required for plaque regression. Trem2 deletion impeded necrotic core resolution, leading us to interrogate the efferocytic capacity of TREM2+ cells during lipid lowering. An in vitro model of cholesterol-experienced ex-lipid associated macrophages (Ex-LAMs) demonstrated that prior lipid priming enhanced efferocytic ability after unloading lipids and maintained expression of lysosomal and cytoskeletal remodeling genes. Augmented TREM2 signaling through genetic models or agonist treatment accelerated efferocytic ability in vitro and plaque regression in vivo. Thus, we posit that a TREM2-dependent ExLAM programming drives atherosclerosis resolution and facilitates beneficial plaque remodeling through enhanced efferocytosis. Overall, targeting the TREM2 pathway may be a viable strategy for stabilizing atherosclerotic plaques in patients treated with aggressive cholesterol control.

immunology↗

bioRxiv2026

Temporal Indexing of Motor Memory

Humans must store and retrieve distinct implicit motor memories in different contexts. Recent research has revealed the motor adaptation system's sensitivity to contextual cues related to posture, spatial goals, and visual inputs. However, to date, the role of one critical variable in implicit motor memory retrieval - the passage of time - remains underexplored, even though it is arguably more fundamental. Here we ask if different temporal intervals can act as effective contextual cues for retrieving competing motor adaptation memories at the subsecond level. We combined a visuomotor dual adaptation paradigm with a 'set-go' task to link opposite perturbation contexts with different movement preparation intervals. The preparation intervals (and their associated perturbations) were randomly interleaved during training, leading to consistent interference. After training, a testing phase revealed robust contextual modulation effects, such that distinct implicit motor memories were retrieved based on the time elapsed during the pre-movement preparatory interval. These contextual memory effects generalized to novel preparatory intervals in a highly structured fashion. Contextual motor memory separation was seen both when elapsed time had to be internally tracked (high uncertainty) and when it was aided by visual and symbolic cues (low uncertainty). Learning and generalization data across experiments could be parsimoniously explained by a computational model that indexed motor memories via a cerebellar granule-cell-like temporal basis set that tiled the delay interval. Our findings suggest that intrinsic timing processes in the cerebellum may function to index motor memories and generalize those memories to new temporal contexts.

neuroscience↗

bioRxiv2026

Adrenal Gland Macrophage-derived TGF-β Governs Vascular Permeability to Drive Monocyte Recruitment during Stress

The adrenal glands are central regulators of systemic stress responses through tightly controlled glucocorticoid production. Yet, the contribution of local immune-vascular interactions to adrenal stress adaptation remains poorly understood. Here, we investigated the role of adrenal gland macrophages in coordinating stress-induced immune remodeling and vascular function. By integrating single-cell RNA sequencing datasets across four distinct stress models, including acute cold exposure, chronic social defeat, chronic inflammation, and systemic Candida albicans infection, we identified a conserved increase in monocyte recruitment to the adrenal gland, accompanied by dynamic macrophage transitions. Comparative transcriptomic and ligand-receptor analyses identified transforming growth factor-{beta} (TGF{beta}) as a dominant macrophage-derived signal targeting adrenal endothelial cells across all stress conditions. Pharmacological blockade of TGF{beta} receptor signaling reduced endothelial activation, vascular permeability, and monocyte infiltration into the adrenal gland following stress, without directly altering resident macrophage numbers. Using genetic fate-mapping and conditional knockout models, we demonstrate that macrophage-derived, but not endothelial-derived, TGF{beta} is required to promote enhanced endothelial adhesion molecule expression, vascular fenestration, permeability, and efficient monocyte recruitment. Loss of macrophage TGF{beta} production also led to exacerbated systemic stress hormone levels. Together, these findings uncover a previously unrecognized macrophage-endothelial axis in the adrenal gland, whereby macrophage-derived TGF{beta} regulates vascular properties to support immune cell recruitment and stress adaptation. This immune-vascular crosstalk provides new mechanistic insights into adrenal homeostasis and suggests potential therapeutic avenues for disorders associated with dysregulated chronic stress.

immunology↗

bioRxiv2026

Complement 3a Receptor mediates high fat diet induced hypothalamic accumulation of lipid associated microglia to regulate neuroinflammation and obesity

Microglia, the resident macrophages of the central nervous system, are recognized for their heterogeneity and integral role in brain function and diseases. In the context of high fat diet (HFD) feeding and obesity, microglia become overactive, acquiring a prevailing lipid associated microglial phenotype (also known as LAM). Yet, how microgliosis is induced and regulated remains unclear. Here we report a key role for the Complement 3a Receptor (C3aR), on HFD-induced hypothalamic gliosis and weight gain in mice. HFD consumption leads to elevated microglial expression of C3aR, which parallels widespread accumulation of reactive microglia, selectively in the hypothalamus. Conditional microglial C3aR deletion protects mice from HFD-induced hypothalamic reactive microgliosis. C3aR deletion or pharmacological antagonism opposes HFD-induced weight gain in male but not female mice. Mechanistically, we demonstrated that C3aR is essential for lipid-induced lipid droplet formation, and acquisition of a LAM molecular signature. In summary, we uncovered a previously unknown role for C3aR in the acquisition of a LAM signature driving diet-induced gliosis, identifying this receptor as a new viable therapeutic candidate for conditions associated with hypothalamic neuroinflammation.

immunology↗

bioRxiv2025

Linking Motor Working Memory to Explicit and Implicit Motor Learning

While explicit and implicit motor learning have been widely studied, the extent to which working memory for recent movements - motor working memory (MWM) - contributes to these processes remains unclear. Previous research suggests that visuospatial working memory may facilitate explicit motor learning but is either uninvolved in or detrimental to implicit learning. Here, we ask if and how these findings extend to non-visual MWM. Based on recent work pointing to separate effector-independent and effector-specific MWM codes, we hypothesized that: (1) explicit motor learning processes would correlate with effector-independent MWM, and (2) implicit motor learning processes would correlate with effector-specific MWM. To test these hypotheses, human participants completed both a MWM task and a visuomotor adaptation task. Our results revealed significant correlations between the quality of effector-independent MWM and the degree of explicit motor learning, extending previous findings on visuospatial working memory. Additionally, we present evidence supporting our second hypothesis, that effector-specific MWM correlates with implicit motor learning.

neuroscience↗

bioRxiv2024

Identification of conserved and tissue-restricted transcriptional profiles for lipid associated macrophages (LAMs)

Macrophages are essential immune cells present in all tissues, and are vital for maintaining tissue homeostasis, immune surveillance, and immune responses. Considerable efforts have identified shared and tissue-specific gene programs for macrophages across organs during homeostasis. This information has dramatically enhanced our understanding of tissue-restricted macrophage programming and function. However, few studies have addressed the overlapping and tissue-specific responses of macrophage subsets following inflammatory responses. One subset of macrophages that has been observed across several studies, lipid-associated macrophages (LAMs), have gained interest due to their unique role in lipid metabolism and potential as a therapeutic target. LAMs have been associated with regulating disease outcomes in metabolically related disorders including atherosclerosis, obesity, and nonalcoholic fatty liver disease (NAFLD). In this study, we utilized single-cell RNA sequencing (scRNAseq) data to profile LAMs across multiple tissues and sterile inflammatory conditions in mice and humans. Integration of data from various disease models revealed that LAMs share a set of conserved transcriptional profiles, including Trem2 and Lpl, but also identified key sets of tissue-specific LAM gene programs. Importantly, the shared LAM markers were highly conserved with human LAM populations that also emerge in chronic inflammatory settings. Overall, this analysis provides a detailed transcriptional landscape of tissue-restricted and shared LAM gene programs and offers insights into their roles in metabolic and chronic inflammatory diseases. These data may help instruct appropriate targets for broad or tissue-restricted therapeutic interventions to modulate LAM populations in disease.

immunology↗

bioRxiv2024

A novel method for characterizing cell-cell interactions at single-cell resolution reveals unique signatures in blood T cell-monocyte complexes during infection

Communication between immune cells through direct contact is a critical feature of immune responses. Here, we developed a novel high-throughput method to study the transcriptome and adaptive immune receptor repertoire of single cells forming complexes without needing bioinformatic deconvolution. We found that T cells and monocytes forming complexes in blood during active tuberculosis (TB) and dengue hold unique transcriptomic signatures indicative of TCR/MCH-II immune synapses. Additionally, T cells in complexes showed enrichment for effector phenotypes, imaging and transcriptomic features of active TCR signaling, and increased immune activity at diagnosis compared to after anti-TB therapy. We also found evidence for bidirectional RNA exchange between T cells and monocytes, since complexes were markedly enriched for "dual-expressing" cells (i.e., co-expressing T cell and monocyte genes). Thus, studying immune cell complexes at a single-cell resolution offers novel perspectives on immune synaptic interactions occurring in blood during infection. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=59 SRC="FIGDIR/small/612103v1_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@f90023org.highwire.dtl.DTLVardef@178007corg.highwire.dtl.DTLVardef@167e53corg.highwire.dtl.DTLVardef@1faff48_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2023

Trem2 Agonist Reprograms Foamy Macrophages to Promote Atherosclerotic Plaque Stability

ObjectiveTrem2, a surface lipid receptor, is expressed on foamy macrophages within atherosclerotic lesions and regulates cell survival, proliferation, and anti-inflammatory responses. Studies examining the role of Trem2 in atherosclerosis have shown that deletion of Trem2 leads to impaired foamy macrophage lipid uptake, proliferation, survival, and cholesterol efflux. Thus, we tested the hypothesis that administration of a validated Trem2 agonist antibody (AL002a) to atherogenic mice could drive macrophage survival and decrease necrotic core formation to improve plaque stability. Approach and ResultsTo model a therapeutic intervention approach, atherosclerosis-prone mice (Ldlr-/-) were fed a high fat diet (HFD) for 8 weeks, then transitioned to treatment with AL002a or isotype control for an additional 8 weeks while continuing on an HFD. AL002a-treated mice had increased lesion size in both the aortic sinus and whole mount aorta, which correlated with an expansion of plaque macrophage area. This expansion was due to increased macrophage survival and proliferation in plaques. Importantly, plaques from AL002a-treated mice showed improved features of plaque stability, including smaller necrotic cores, increased fibrous caps, and greater collagen deposition. Single cell RNA sequencing of whole aorta suspensions from isotype and AL002a-treated atherosclerotic mice revealed that Trem2 agonism dramatically altered foamy macrophage transcriptome. This included upregulation of oxidative phosphorylation and increased expression of collagen genes. In vitro studies validated that Trem2-agonism with AL002a promoted foamy macrophage oxLDL uptake, survival, and cholesterol efflux in culture. ConclusionsTrem2 agonist expands plaque macrophages by promoting cell survival and proliferation but improves features of plaque stability by rewiring foamy macrophage function to enhance collagen deposition.

immunology↗

bioRxiv2020

Narratives: fMRI data for evaluating models of naturalistic language comprehension

The "Narratives" collection aggregates a variety of functional MRI datasets collected while human subjects listened to naturalistic spoken stories. The current release includes 345 subjects, 891 functional scans, and 27 diverse stories of varying duration totaling ~4.6 hours of unique stimuli (~43,000 words). This data collection is well-suited for naturalistic neuroimaging analysis, and is intended to serve as a benchmark for models of language and narrative comprehension. We provide standardized MRI data accompanied by rich metadata, preprocessed versions of the data ready for immediate use, and the spoken story stimuli with time-stamped phoneme- and word-level transcripts. All code and data are publicly available with full provenance in keeping with current best practices in transparent and reproducible neuroimaging.

neuroscience↗

bioRxiv2020

Siderophore-mediated zinc acquisition enhances enterobacterial colonization of the inflamed gut.

Zinc is an essential cofactor for bacterial metabolism, and many Enterobacteriaceae express the zinc transporters ZnuABC and ZupT to acquire this metal in the host. Unexpectedly, the probiotic bacterium Escherichia coli Nissle 1917 exhibited appreciable growth in zinc-limited media even when these transporters were deleted. By utilizing in vitro and in vivo studies, as well as native spray metal infusion mass spectrometry and ion identity molecular networking, we discovered that Nissle utilizes yersiniabactin as a zincophore. Indeed, yersiniabactin enables Nissle to scavenge zinc in zinc-limited media, to resist calprotectin-mediated zinc sequestration, and to thrive in the inflamed gut. Moreover, we discovered that yersiniabactins affinity for iron or zinc changes in a pH-dependent manner, with higher affinity for zinc as the pH increased. Altogether, we demonstrate that siderophore metal affinity can be influenced by the local environment and reveal a mechanism of zinc acquisition available to many commensal and pathogenic Enterobacteriaceae.

microbiology↗

bioRxiv2020

Think Like an Expert: Neural Alignment Predicts Understanding in Students Taking an Introduction to Computer Science Course

How do students understand and remember new information? Despite major advances in measuring human brain activity during and after educational experiences, it is unclear how learners internalize new content, especially in real-life and online settings. In this work, we introduce a neural measure for predicting and assessing learning outcomes. Our approach hinges on the idea that successful learning involves forming the "right" set of neural representations, which are captured in "canonical" activity patterns shared across individuals. Specifically, we hypothesized that understanding is mirrored in "neural alignment": the degree to which an individual learners neural representations match those of experts, as well as those of other learners. We tested this hypothesis in a longitudinal functional MRI study that regularly scanned college students enrolled in an introduction to computer science course. We additionally scanned graduate student "experts" in computer science. We found that alignment among students successfully predicted overall performance in a final exam. Furthermore, within individual students, concepts that evoked better alignment with the experts and with their fellow students were better understood, revealing neural patterns associated with understanding specific concepts. These results provide support for a novel neural measure of concept understanding that can be used to assess and predict learning outcomes in real-life contexts.

neuroscience↗

bioRxiv2019

Leveraging shared connectivity to aggregate heterogeneous datasets into a common response space

Connectivity hyperalignment can be used to estimate a single shared response space across disjoint datasets. We develop a connectivity-based shared response model that factorizes aggregated fMRI datasets into a single reduced-dimension shared connectivity space and subject-specific topographic transformations. These transformations resolve idiosyncratic functional topographies and can be used to project response time series into shared space. We evaluate this algorithm on a large collection of heterogeneous, naturalistic fMRI datasets acquired while subjects listened to spoken stories. Projecting subject data into shared space dramatically improves between-subject story time-segment classification and increases the dimensionality of shared information across subjects. This improvement generalizes to subjects and stories excluded when estimating the shared space. We demonstrate that estimating a simple semantic encoding model in shared space improves between-subject forward encoding and inverted encoding model performance. The shared space estimated across all datasets is distinct from the shared space derived from any particular constituent dataset; the algorithm leverages shared connectivity to yield a consensus shared space conjoining diverse story stimuli.\n\nHighlightsO_LIConnectivity SRM estimates a single shared space across subjects and stimuli\nC_LIO_LITopographic transformations resolve idiosyncrasies across individuals\nC_LIO_LIShared connectivity space enhances spatiotemporal intersubject correlations\nC_LIO_LISemantic model-based encoding and decoding improves across subjects\nC_LIO_LITransformations project into a consensus space conjoining diverse stimuli\nC_LI

neuroscience↗