Chen, J;Gannot, N;Li, X;Zhu, R;Zhang, C;Li, P;
PMID: 36522525 | DOI: 10.1007/s12264-022-00994-8
The parabrachial nucleus (PBN) integrates interoceptive and exteroceptive information to control various behavioral and physiological processes including breathing, emotion, and sleep/wake regulation through the neural circuits that connect to the forebrain and the brainstem. However, the precise identity and function of distinct PBN subpopulations are still largely unknown. Here, we leveraged molecular characterization, retrograde tracing, optogenetics, chemogenetics, and electrocortical recording approaches to identify a small subpopulation of neurotensin-expressing neurons in the PBN that largely project to the emotional control regions in the forebrain, rather than the medulla. Their activation induces freezing and anxiety-like behaviors, which in turn result in tachypnea. In addition, optogenetic and chemogenetic manipulations of these neurons revealed their function in promoting wakefulness and maintaining sleep architecture. We propose that these neurons comprise a PBN subpopulation with specific gene expression, connectivity, and function, which play essential roles in behavioral and physiological regulation.
Smith, RJ;Liang, M;Loe, AKH;Yung, T;Kim, JE;Hudson, M;Wilson, MD;Kim, TH;
PMID: 36717563 | DOI: 10.1038/s41467-023-36228-2
Epithelial-mesenchymal signaling in the gastrointestinal system is vital in establishing regional identity during organogenesis and maintaining adult stem cell homeostasis. Although recent work has demonstrated that Wnt ligands expressed by mesenchymal cells are required during gastrointestinal development and stem cell homeostasis, epigenetic mechanisms driving spatiotemporal control of crosstalk remain unknown. Here, we demonstrate that gastrointestinal mesenchymal cells control epithelial fate and function through Polycomb Repressive Complex 2-mediated chromatin bivalency. We find that while key lineage-determining genes possess tissue-specific chromatin accessibility, Polycomb Repressive Complex 2 controls Wnt expression in mesenchymal cells without altering accessibility. We show that reduction of mesenchymal Wnt secretion rescues gastrointestinal fate and proliferation defects caused by Polycomb Repressive Complex 2 loss. We demonstrate that mesenchymal Polycomb Repressive Complex 2 also regulates niche signals to maintain stem cell function in the adult intestine. Our results highlight a broadly permissive chromatin architecture underlying regionalization in mesenchymal cells, then demonstrate further how chromatin architecture in niches can influence the fate and function of neighboring cells.
The circadian clock gene, Bmal1, regulates intestinal stem cell signaling and represses tumor initiation
Cellular and molecular gastroenterology and hepatology
Stokes, K;Nunes, M;Trombley, C;Flôres, DEFL;Wu, G;Taleb, Z;Alkhateeb, A;Banskota, S;Harris, C;Love, OP;Khan, WI;Rueda, L;Hogenesch, JB;Karpowicz, P;
PMID: 34534703 | DOI: 10.1016/j.jcmgh.2021.08.001
Circadian rhythms are daily physiological oscillations driven by the circadian clock: a 24-hour transcriptional timekeeper that regulates hormones, inflammation, and metabolism. Circadian rhythms are known to be important for health, but whether their loss contributes to colorectal cancer is not known.We tested the non-redundant clock gene, Bmal1, in intestinal homeostasis and tumorigenesis, using the Apcmin model of colorectal cancer.Bmal1 mutant, epithelium-conditional Bmal1 mutant, and photoperiod-disrupted mice bearing the Apcmin allele were assessed for tumorigenesis. Tumors and normal non-transformed tissue were characterized. Intestinal organoids were assessed for circadian transcription rhythms by RNA-sequencing, and in vivo and organoid assays were used to test Bmal1-dependent proliferation and self-renewal.Loss of Bmal1 or circadian photoperiod increases tumor initiation. In the intestinal epithelium the clock regulates transcripts involved in regeneration and intestinal stem cell signaling. Tumors have no self-autonomous clock function and only weak clock function in vivo. Apcmin clock-disrupted tumors exhibit high Yap (Hippo signaling) activity but exhibit low Wnt activity. Intestinal organoid assays reveal that loss of Bmal1 increases self-renewal in a Yap-dependent manner.Bmal1 regulates intestinal stem cell pathways, including Hippo signaling, and the loss of circadian rhythms potentiates tumor initiation.
Shin, S;You, IJ;Jeong, M;Bae, Y;Wang, XY;Cawley, ML;Han, A;Lim, BK;
PMID: 36510113 | DOI: 10.1038/s41593-022-01208-0
Early-life trauma (ELT) is a risk factor for binge eating and obesity later in life, yet the neural circuits that underlie this association have not been addressed. Here, we show in mice that downregulation of the leptin receptor (Lepr) in the lateral hypothalamus (LH) and its effect on neural activity is crucial in causing ELT-induced binge-like eating and obesity upon high-fat diet exposure. We also found that the increased activity of Lepr-expressing LH (LHLepr) neurons encodes sustained binge-like eating in ELT mice. Inhibition of LHLepr neurons projecting to the ventrolateral periaqueductal gray normalizes these behavioral features of ELT mice. Furthermore, activation of proenkephalin-expressing ventrolateral periaqueductal gray neurons, which receive inhibitory inputs from LHLepr neurons, rescues ELT-induced maladaptive eating habits. Our results identify a circuit pathway that mediates ELT-induced maladaptive eating and may lead to the identification of novel therapeutic targets for binge eating and obesity.
Steuernagel, L;Lam, BYH;Klemm, P;Dowsett, GKC;Bauder, CA;Tadross, JA;Hitschfeld, TS;Del Rio Martin, A;Chen, W;de Solis, AJ;Fenselau, H;Davidsen, P;Cimino, I;Kohnke, SN;Rimmington, D;Coll, AP;Beyer, A;Yeo, GSH;Brüning, JC;
PMID: 36266547 | DOI: 10.1038/s42255-022-00657-y
The hypothalamus plays a key role in coordinating fundamental body functions. Despite recent progress in single-cell technologies, a unified catalog and molecular characterization of the heterogeneous cell types and, specifically, neuronal subtypes in this brain region are still lacking. Here, we present an integrated reference atlas, 'HypoMap,' of the murine hypothalamus, consisting of 384,925 cells, with the ability to incorporate new additional experiments. We validate HypoMap by comparing data collected from Smart-Seq+Fluidigm C1 and bulk RNA sequencing of selected neuronal cell types with different degrees of cellular heterogeneity. Finally, via HypoMap, we identify classes of neurons expressing glucagon-like peptide-1 receptor (Glp1r) and prepronociceptin (Pnoc), and validate them using single-molecule in situ hybridization. Collectively, HypoMap provides a unified framework for the systematic functional annotation of murine hypothalamic cell types, and it can serve as an important platform to unravel the functional organization of hypothalamic neurocircuits and to identify druggable targets for treating metabolic disorders.
Investigative Ophthalmology & Visual Science
Zhu, X;Xu, M;Grachtchouk, M;
RESULTS : Short-term lineage tracing data showed that _Lrig1_, _Lgr6_ and _Axin2_ label basal cells in MG ducts and acini. Long-term lineage tracing results showed that clones of labeled cells persist through multiple rounds of ductal and acinar renewal and give rise to differentiated progeny, identifying _Lrig1_+, _Lgr6_+ and _Axin2+_ ductal and acinar basal cells as self-renewing SCs. Forced expression of GLI2ΔN enhanced basal proliferation, caused expansion of _Lrig1_+ SCs, and lead to replacement of lipid-filled meibocytes by proliferative and poorly differentiated acinar cells. Transcriptional profiling of GLI2ΔN-expressing and control MGs revealed that forced GLI2ΔN expression caused greatly increased expression of _Lrig1_ and _Lgr6_ and suppressed expression of meibocyte differentiation genes.
Furlan, A;Corona, A;Boyle, S;Sharma, R;Rubino, R;Habel, J;Gablenz, EC;Giovanniello, J;Beyaz, S;Janowitz, T;Shea, SD;Li, B;
PMID: 36266470 | DOI: 10.1038/s41593-022-01178-3
Obesity is a global pandemic that is causally linked to many life-threatening diseases. Apart from some rare genetic conditions, the biological drivers of overeating and reduced activity are unclear. Here, we show that neurotensin-expressing neurons in the mouse interstitial nucleus of the posterior limb of the anterior commissure (IPAC), a nucleus of the central extended amygdala, encode dietary preference for unhealthy energy-dense foods. Optogenetic activation of IPACNts neurons promotes obesogenic behaviors, such as hedonic eating, and modulates food preference. Conversely, acute inhibition of IPACNts neurons reduces feeding and decreases hedonic eating. Chronic inactivation of IPACNts neurons recapitulates these effects, reduces preference for sweet, non-caloric tastants and, furthermore, enhances locomotion and energy expenditure; as a result, mice display long-term weight loss and improved metabolic health and are protected from obesity. Thus, the activity of a single neuronal population bidirectionally regulates energy homeostasis. Our findings could lead to new therapeutic strategies to prevent and treat obesity.
Martin, M;Vermeiren, S;Bostaille, N;Eubelen, M;Spitzer, D;Vermeersch, M;Profaci, CP;Pozuelo, E;Toussay, X;Raman-Nair, J;Tebabi, P;America, M;De Groote, A;Sanderson, LE;Cabochette, P;Germano, RFV;Torres, D;Boutry, S;de Kerchove d'Exaerde, A;Bellefroid, EJ;Phoenix, TN;Devraj, K;Lacoste, B;Daneman, R;Liebner, S;Vanhollebeke, B;
PMID: 35175798 | DOI: 10.1126/science.abm4459
The blood-brain barrier (BBB) protects the central nervous system (CNS) from harmful blood-borne factors. Although BBB dysfunction is a hallmark of several neurological disorders, therapies to restore BBB function are lacking. An attractive strategy is to repurpose developmental BBB regulators, such as Wnt7a, into BBB-protective agents. However, safe therapeutic use of Wnt ligands is complicated by their pleiotropic Frizzled signaling activities. Taking advantage of the Wnt7a/b-specific Gpr124/Reck co-receptor complex, we genetically engineered Wnt7a ligands into BBB-specific Wnt activators. In a "hit-and-run" adeno-associated virus-assisted CNS gene delivery setting, these new Gpr124/Reck-specific agonists protected BBB function, thereby mitigating glioblastoma expansion and ischemic stroke infarction. This work reveals that the signaling specificity of Wnt ligands is adjustable and defines a modality to treat CNS disorders by normalizing the BBB.
