Dong, X;Limjunyawong, N;Sypek, EI;Wang, G;Ortines, RV;Youn, C;Alphonse, MP;Dikeman, D;Wang, Y;Lay, M;Kothari, R;Vasavda, C;Pundir, P;Goff, L;Miller, LS;Lu, W;Garza, LA;Kim, BS;Archer, NK;Dong, X;
PMID: 35882236 | DOI: 10.1016/j.immuni.2022.06.021
Healthy skin maintains a diverse microbiome and a potent immune system to fight off infections. Here, we discovered that the epithelial-cell-derived antimicrobial peptides defensins activated orphan G-protein-coupled receptors (GPCRs) Mrgpra2a/b on neutrophils. This signaling axis was required for effective neutrophil-mediated skin immunity and microbiome homeostasis. We generated mutant mouse lines lacking the entire Defensin (Def) gene cluster in keratinocytes or Mrgpra2a/b. Def and Mrgpra2 mutant animals both exhibited skin dysbiosis, with reduced microbial diversity and expansion of Staphylococcus species. Defensins and Mrgpra2 were critical for combating S. aureus infections and the formation of neutrophil abscesses, a hallmark of antibacterial immunity. Activation of Mrgpra2 by defensin triggered neutrophil release of IL-1β and CXCL2 which are vital for proper amplification and propagation of the antibacterial immune response. This study demonstrated the importance of epithelial-neutrophil signaling via the defensin-Mrgpra2 axis in maintaining healthy skin ecology and promoting antibacterial host defense.
Hu, B;Lelek, S;Spanjaard, B;El-Sammak, H;Simões, MG;Mintcheva, J;Aliee, H;Schäfer, R;Meyer, AM;Theis, F;Stainier, DYR;Panáková, D;Junker, JP;
PMID: 35864193 | DOI: 10.1038/s41588-022-01129-5
The adult zebrafish heart has a high capacity for regeneration following injury. However, the composition of the regenerative niche has remained largely elusive. Here, we dissected the diversity of activated cell states in the regenerating zebrafish heart based on single-cell transcriptomics and spatiotemporal analysis. We observed the emergence of several transient cell states with fibroblast characteristics following injury, and we outlined the proregenerative function of collagen-12-expressing fibroblasts. To understand the cascade of events leading to heart regeneration, we determined the origin of these cell states by high-throughput lineage tracing. We found that activated fibroblasts were derived from two separate sources: the epicardium and the endocardium. Mechanistically, we determined Wnt signalling as a regulator of the endocardial fibroblast response. In summary, our work identifies specialized activated fibroblast cell states that contribute to heart regeneration, thereby opening up possible approaches to modulating the regenerative capacity of the vertebrate heart.
De Luca, R;Nardone, S;Grace, KP;Venner, A;Cristofolini, M;Bandaru, SS;Sohn, LT;Kong, D;Mochizuki, T;Viberti, B;Zhu, L;Zito, A;Scammell, TE;Saper, CB;Lowell, BB;Fuller, PM;Arrigoni, E;
PMID: 35851580 | DOI: 10.1038/s41467-022-31591-y
Humans and animals lacking orexin neurons exhibit daytime sleepiness, sleep attacks, and state instability. While the circuit basis by which orexin neurons contribute to consolidated wakefulness remains unclear, existing models posit that orexin neurons provide their wake-stabilizing influence by exerting excitatory tone on other brain arousal nodes. Here we show using in vivo optogenetics, in vitro optogenetic-based circuit mapping, and single-cell transcriptomics that orexin neurons also contribute to arousal maintenance through indirect inhibition of sleep-promoting neurons of the ventrolateral preoptic nucleus. Activation of this subcortical circuit rapidly drives wakefulness from sleep by differentially modulating the activity of ventrolateral preoptic neurons. We further identify and characterize a feedforward circuit through which orexin (and co-released glutamate) acts to indirectly target and inhibit sleep-promoting ventrolateral preoptic neurons to produce arousal. This revealed circuitry provides an alternate framework for understanding how orexin neurons contribute to the maintenance of consolidated wakefulness and stabilize behavioral state.
Sipilä, K;Rognoni, E;Jokinen, J;Tewary, M;Vietri Rudan, M;Talvi, S;Jokinen, V;Dahlström, KM;Liakath-Ali, K;Mobasseri, A;Du-Harpur, X;Käpylä, J;Nutt, SL;Salminen, TA;Heino, J;Watt, FM;
PMID: 35671757 | DOI: 10.1016/j.devcel.2022.05.011
Stem cell renewal and differentiation are regulated by interactions with the niche. Although multiple cell populations have been identified in distinct anatomical compartments, little is known about niche-specific molecular factors. Using skin as a model system and combining single-cell RNA-seq data analysis, immunofluorescence, and transgenic mouse models, we show that the transmembrane protein embigin is specifically expressed in the sebaceous gland and that the number of embigin-expressing cells is negatively regulated by Wnt. The loss of embigin promotes exit from the progenitor compartment and progression toward differentiation, and also compromises lipid metabolism. Embigin modulates sebaceous niche architecture by affecting extracellular matrix organization and basolateral targeting of monocarboxylate transport. We discover through ligand screening that embigin is a direct fibronectin receptor, binding to the N-terminal fibronectin domain without impairing integrin function. Our results solve the long-standing question of how embigin regulates cell adhesion and demonstrate a mechanism that couples adhesion and metabolism.
Sinha, T;Lammerts van Bueren, K;Dickel, DE;Zlatanova, I;Thomas, R;Lizama, CO;Xu, SM;Zovein, AC;Ikegami, K;Moskowitz, IP;Pollard, KS;Pennacchio, LA;Black, BL;
PMID: 35649376 | DOI: 10.1016/j.celrep.2022.110881
Endothelial and erythropoietic lineages arise from a common developmental progenitor. Etv2 is a master transcriptional regulator required for the development of both lineages. However, the mechanisms through which Etv2 initiates the gene-regulatory networks (GRNs) for endothelial and erythropoietic specification and how the two GRNs diverge downstream of Etv2 remain incompletely understood. Here, by analyzing a hypomorphic Etv2 mutant, we demonstrate different threshold requirements for initiation of the downstream GRNs for endothelial and erythropoietic development. We show that Etv2 functions directly in a coherent feedforward transcriptional network for vascular endothelial development, and a low level of Etv2 expression is sufficient to induce and sustain the endothelial GRN. In contrast, Etv2 induces the erythropoietic GRN indirectly via activation of Tal1, which requires a significantly higher threshold of Etv2 to initiate and sustain erythropoietic development. These results provide important mechanistic insight into the divergence of the endothelial and erythropoietic lineages.
Mu, R;Tang, S;Han, X;Wang, H;Yuan, D;Zhao, J;Long, Y;Hong, H;
PMID: 35649349 | DOI: 10.1016/j.celrep.2022.110882
Generalization of visual aversion is a critical function of the brain that supports survival, but the underlying neurobiological mechanisms are unclear. We establish a rapid generalization procedure for inducing visual aversion by dynamic stripe images. By using fiber photometry, apoptosis, chemogenetic and optogenetic techniques, and behavioral tests, we find that decreased cholinergic neurons' activity in the medial septum (MS) leads to generalization loss of visual aversion. Strikingly, we identify a projection from MS cholinergic neurons to the medial habenula (MHb) and find that inhibition of the MS→MHb cholinergic circuit disrupts aversion-generalization formation while its continuous activation disrupts subsequent extinction. Further studies show that MS→MHb cholinergic projections modulate the generalization of visual aversion possibly via M1 muscarinic acetylcholine receptors (mAChRs) of downstream neurons coreleasing glutamate and acetylcholine. These findings reveal that the MS→MHb cholinergic circuit is a critical node in aversion-generalization formation and extinction and potentially provides insight into the pathogenesis of affective disorders.
Bolkan, SS;Stone, IR;Pinto, L;Ashwood, ZC;Iravedra Garcia, JM;Herman, AL;Singh, P;Bandi, A;Cox, J;Zimmerman, CA;Cho, JR;Engelhard, B;Pillow, JW;Witten, IB;
PMID: 35260863 | DOI: 10.1038/s41593-022-01021-9
A classic view of the striatum holds that activity in direct and indirect pathways oppositely modulates motor output. Whether this involves direct control of movement, or reflects a cognitive process underlying movement, remains unresolved. Here we find that strong, opponent control of behavior by the two pathways of the dorsomedial striatum depends on the cognitive requirements of a task. Furthermore, a latent state model (a hidden Markov model with generalized linear model observations) reveals that-even within a single task-the contribution of the two pathways to behavior is state dependent. Specifically, the two pathways have large contributions in one of two states associated with a strategy of evidence accumulation, compared to a state associated with a strategy of repeating previous choices. Thus, both the demands imposed by a task, as well as the internal state of mice when performing a task, determine whether dorsomedial striatum pathways provide strong and opponent control of behavior.
Thomas, K;Henley, T;Rossi, S;Costello, MJ;Polacheck, W;Griffith, BE;Bressan, M;
PMID: 33891897 | DOI: 10.1016/j.devcel.2021.04.004
Cardiac pacemaker cells (CPCs) rhythmically initiate the electrical impulses that drive heart contraction. CPCs display the highest rate of spontaneous depolarization in the heart despite being subjected to inhibitory electrochemical conditions that should theoretically suppress their activity. While several models have been proposed to explain this apparent paradox, the actual molecular mechanisms that allow CPCs to overcome electrogenic barriers to their function remain poorly understood. Here, we have traced CPC development at single-cell resolution and uncovered a series of cytoarchitectural patterning events that are critical for proper pacemaking. Specifically, our data reveal that CPCs dynamically modulate adherens junction (AJ) engagement to control characteristics including surface area, volume, and gap junctional coupling. This allows CPCs to adopt a structural configuration that supports their overall excitability. Thus, our data have identified a direct role for local cellular mechanics in patterning critical morphological features that are necessary for CPC electrical activity.
Stenudd, M;Sabelström, H;Llorens-Bobadilla, E;Zamboni, M;Blom, H;Brismar, H;Zhang, S;Basak, O;Clevers, H;Göritz, C;Barnabé-Heider, F;Frisén, J;
PMID: 35235796 | DOI: 10.1016/j.celrep.2022.110440
Spinal cord ependymal cells display neural stem cell properties in vitro and generate scar-forming astrocytes and remyelinating oligodendrocytes after injury. We report that ependymal cells are functionally heterogeneous and identify a small subpopulation (8% of ependymal cells and 0.1% of all cells in a spinal cord segment), which we denote ependymal A (EpA) cells, that accounts for the in vitro stem cell potential in the adult spinal cord. After spinal cord injury, EpA cells undergo self-renewing cell division as they give rise to differentiated progeny. Single-cell transcriptome analysis revealed a loss of ependymal cell gene expression programs as EpA cells gained signaling entropy and dedifferentiated to a stem-cell-like transcriptional state after an injury. We conclude that EpA cells are highly differentiated cells that can revert to a stem cell state and constitute a therapeutic target for spinal cord repair.
Yu, H;Rubinstein, M;Low, MJ;
PMID: 35044906 | DOI: 10.7554/eLife.72883
Proopiomelanocortin (POMC) neurons of the hypothalamic arcuate nucleus are essential to regulate food intake and energy balance. However, the ontogenetic transcriptional programs that specify the identity and functioning of these neurons are poorly understood. Here, we use single-cell RNA-sequencing (scRNA-seq) to define the transcriptomes characterizing Pomc-expressing cells in the developing hypothalamus and translating ribosome affinity purification with RNA-sequencing (TRAP-seq) to analyze the subsequent translatomes of mature POMC neurons. Our data showed that Pomc-expressing neurons give rise to multiple developmental pathways expressing different levels of Pomc and unique combinations of transcription factors. The predominant cluster, featured by high levels of Pomc and Prdm12 transcripts, represents the canonical arcuate POMC neurons. Additional cell clusters expressing medium or low levels of Pomc mature into different neuronal phenotypes featured by distinct sets of transcription factors, neuropeptides, processing enzymes, cell surface, and nuclear receptors. We conclude that the genetic programs specifying the identity and differentiation of arcuate POMC neurons are diverse and generate a heterogeneous repertoire of neuronal phenotypes early in development that continue to mature postnatally.
Guilliams, M;Bonnardel, J;Haest, B;Vanderborght, B;Wagner, C;Remmerie, A;Bujko, A;Martens, L;Thoné, T;Browaeys, R;De Ponti, FF;Vanneste, B;Zwicker, C;Svedberg, FR;Vanhalewyn, T;Gonçalves, A;Lippens, S;Devriendt, B;Cox, E;Ferrero, G;Wittamer, V;Willaert, A;Kaptein, SJF;Neyts, J;Dallmeier, K;Geldhof, P;Casaert, S;Deplancke, B;Ten Dijke, P;Hoorens, A;Vanlander, A;Berrevoet, F;Van Nieuwenhove, Y;Saeys, Y;Saelens, W;Van Vlierberghe, H;Devisscher, L;Scott, CL;
PMID: 35021063 | DOI: 10.1016/j.cell.2021.12.018
The liver is the largest solid organ in the body, yet it remains incompletely characterized. Here we present a spatial proteogenomic atlas of the healthy and obese human and murine liver combining single-cell CITE-seq, single-nuclei sequencing, spatial transcriptomics, and spatial proteomics. By integrating these multi-omic datasets, we provide validated strategies to reliably discriminate and localize all hepatic cells, including a population of lipid-associated macrophages (LAMs) at the bile ducts. We then align this atlas across seven species, revealing the conserved program of bona fide Kupffer cells and LAMs. We also uncover the respective spatially resolved cellular niches of these macrophages and the microenvironmental circuits driving their unique transcriptomic identities. We demonstrate that LAMs are induced by local lipid exposure, leading to their induction in steatotic regions of the murine and human liver, while Kupffer cell development crucially depends on their cross-talk with hepatic stellate cells via the evolutionarily conserved ALK1-BMP9/10 axis.
Buchanan, KL;Rupprecht, LE;Kaelberer, MM;Sahasrabudhe, A;Klein, ME;Villalobos, JA;Liu, WW;Yang, A;Gelman, J;Park, S;Anikeeva, P;Bohórquez, DV;
PMID: 35027761 | DOI: 10.1038/s41593-021-00982-7
Guided by gut sensory cues, humans and animals prefer nutritive sugars over non-caloric sweeteners, but how the gut steers such preferences remains unknown. In the intestine, neuropod cells synapse with vagal neurons to convey sugar stimuli to the brain within seconds. Here, we found that cholecystokinin (CCK)-labeled duodenal neuropod cells differentiate and transduce luminal stimuli from sweeteners and sugars to the vagus nerve using sweet taste receptors and sodium glucose transporters. The two stimulus types elicited distinct neural pathways: while sweetener stimulated purinergic neurotransmission, sugar stimulated glutamatergic neurotransmission. To probe the contribution of these cells to behavior, we developed optogenetics for the gut lumen by engineering a flexible fiberoptic. We showed that preference for sugar over sweetener in mice depends on neuropod cell glutamatergic signaling. By swiftly discerning the precise identity of nutrient stimuli, gut neuropod cells serve as the entry point to guide nutritive choices.
