Expression Dynamics and Functions of Hes Factors in Development and Diseases

RIP140 regulates transcription factor HES1 oscillatory expression and mitogenic activity in colon cancer cells

The transcription factor receptor-interacting protein 140 (RIP140) regulates intestinal homeostasis and tumorigenesis through Wnt signaling. In this study, we investigated its effect on the Notch/HES1 signaling pathway. In colorectal cancer (CRC) cell lines, RIP140 positively regulated HES1 gene expression at the transcriptional level via a recombining binding protein suppressor of hairless (RBPJ)/neurogenic locus notch homolog protein 1 (NICD)-mediated mechanism. In support of these in vitro data, RIP140 and HES1 expression significantly correlated in mouse intestine and in a cohort of CRC samples, thus supporting the positive regulation of HES1 gene expression by RIP140. Interestingly, when the Notch pathway is fully activated, RIP140 exerted a strong inhibition of HES1 gene transcription controlled by the level of HES1 itself. Moreover, RIP140 directly interacts with HES1 and reversed its mitogenic activity in human CRC cells. In line with this observation, HES1 levels were associated with a better patient survival only when tumors expressed high levels of RIP140. Our data identify RIP140 as a key regulator of the Notch/HES1 signaling pathway, with a dual effect on HES1 gene expression at the transcriptional level and a strong impact on colon cancer cell proliferation.

NOTCH2 promotes osteoclast maturation and metabolism and modulates the transcriptome profile during osteoclastogenesis

Notch signaling plays a key regulatory role in bone remodeling and NOTCH2 enhances osteoclastogenesis, an effect that is mostly mediated by its target gene Hes1. In the present study, we explored mechanisms responsible for the enhanced osteoclastogenesis in bone marrow-derived macrophages (BMM) from Notch2tm1.1Ecan, harboring a NOTCH2 gain-of-function mutation, and control mice. Notch2tm1.1Ecan mice are osteopenic and have enhanced osteoclastogenesis. Bulk RNA-Seq and gene set enrichment analysis of Notch2tm1.1Ecan BMMs cultured in the presence of macrophage colony stimulating factor (M-CSF) and receptor activator of NF-κB ligand revealed enrichment of genes associated with enhanced cell metabolism, aerobic respiration, and mitochondrial function, all associated with osteoclastogenesis. These pathways were not enhanced in the context of a Hes1 inactivation. Analysis of single cell RNA-Seq data of pooled control and Notch2tm1.1Ecan BMMs treated with M-CSF or M-CSF and receptor activator of NF-κB ligand for 3 days identified 11 well-defined cellular clusters. Pseudotime trajectory analysis indicated a trajectory of clusters expressing genes associated with osteoclast progenitors, osteoclast precursors, and mature cells. There were an increased number of cells expressing gene markers associated with the osteoclast and with an unknown, albeit related, cluster in Notch2tm1.1Ecan than in control BMMs as well as enhanced expression of genes associated with osteoclast progenitors and precursors in Notch2tm1.1Ecan cells. In conclusion, BMM cultures display cellular heterogeneity, and NOTCH2 enhances osteoclastogenesis, increases mitochondrial and metabolic activity of osteoclasts, and affects cell cluster allocation in BMMs.

NOTCH2 sensitizes the chondrocyte to the inflammatory response of tumor necrosis factor α

Notch regulates the immune and inflammatory response and has been associated with the pathogenesis of osteoarthritis in humans and preclinical models of the disease. Notch2tm1.1Ecan mice harbor a NOTCH2 gain-of-function and are sensitized to osteoarthritis, but the mechanisms have not been explored. We examined the effects of tumor necrosis factor α (TNFα) in chondrocytes from Notch2tm1.1Ecan mice and found that NOTCH2 enhanced the effect of TNFα on Il6 and Il1b expression. Similar results were obtained in cells from a conditional model of NOTCH2 gain-of-function, Notch22.1Ecan mice, and following the expression of the NOTCH2 intracellular domain in vitro. Recombination signal-binding protein for immunoglobulin Kappa J region partners with the NOTCH2 intracellular domain to activate transcription; in the absence of Notch signaling it inhibits transcription, and Rbpj inactivation in chondrocytes resulted in Il6 induction. Although TNFα induced IL6 to a greater extent in the context of NOTCH2 activation, there was a concomitant inhibition of Notch target genes Hes1, Hey1, Hey2, and Heyl. Electrophoretic mobility shift assay demonstrated displacement of recombination signal-binding protein for immunoglobulin Kappa J region from DNA binding sites by TNFα explaining the increased Il6 expression and the concomitant decrease in Notch target genes. NOTCH2 enhanced the effect of TNFα on NF-κB signaling, and RNA-Seq revealed increased expression of pathways associated with inflammation and the phagosome in NOTCH2 overexpressing cells in the absence and presence of TNFα. Collectively, NOTCH2 has important interactions with TNFα resulting in the enhanced expression of Il6 and inflammatory pathways in chondrocytes.

Single-cell RNA sequencing reveals new subtypes of lens superficial tissue in humans

Although the cell atlas of the human ocular anterior segment of the human eye was revealed by single-nucleus RNA sequencing, whether subtypes of lens stem/progenitor cells exist among epithelial cells and the molecular characteristics of cell differentiation of the human lens remain unclear. Single-cell RNA sequencing is a powerful tool to analyse the heterogeneity of tissues at the single cell level, leading to a better understanding of the processes of cell differentiation. By profiling 18,596 cells in human lens superficial tissue through single-cell sequencing, we identified two subtypes of lens epithelial cells that specifically expressed C8orf4 and ADAMTSL4 with distinct spatial localization, a new type of fibre cells located directly adjacent to the epithelium, and a subpopulation of ADAMTSL4+ cells that might be lens epithelial stem/progenitor cells. We also found two trajectories of lens epithelial cell differentiation and changes of some important genes during differentiation.

Temporospatial inhibition of Erk signaling is required for lymphatic valve formation

Intraluminal lymphatic valves (LVs) and lymphovenous valves (LVVs) are critical to ensure the unidirectional flow of lymphatic fluid. Morphological abnormalities in these valves always cause lymph or blood reflux, and result in lymphedema. However, the underlying molecular mechanism of valve development remains poorly understood. We here report the implication of Efnb2-Ephb4-Rasa1 regulated Erk signaling axis in lymphatic valve development with identification of two new valve structures. Dynamic monitoring of phospho-Erk activity indicated that Erk signaling is spatiotemporally inhibited in some lymphatic endothelial cells (LECs) during the valve cell specification. Inhibition of Erk signaling via simultaneous depletion of zygotic erk1 and erk2 or treatment with MEK inhibitor selumetinib causes lymphatic vessel hypoplasia and lymphatic valve hyperplasia, suggesting opposite roles of Erk signaling during these two processes. ephb4b mutants, efnb2a;efnb2b or rasa1a;rasa1b double mutants all have defective LVs and LVVs and exhibit blood reflux into lymphatic vessels with an edema phenotype. Importantly, the valve defects in ephb4b or rasa1a;rasa1b mutants are mitigated with high-level gata2 expression in the presence of MEK inhibitors. Therefore, Efnb2-Ephb4 signaling acts to suppress Erk activation in valve-forming cells to promote valve specification upstream of Rasa1. Not only do our findings reveal a molecular mechanism of lymphatic valve formation, but also provide a basis for the treatment of lymphatic disorders.

Beta cell dysfunction induced by bone morphogenetic protein (BMP)-2 is associated with histone modifications and decreased NeuroD1 chromatin binding

Insufficient insulin secretion is a hallmark of type 2 diabetes and has been attributed to beta cell identity loss characterized by decreased expression of several key beta cell genes. The pro-inflammatory factor BMP-2 is upregulated in islets of Langerhans from individuals with diabetes and acts as an inhibitor of beta cell function and proliferation. Exposure to BMP-2 induces expression of Id1-4, Hes-1, and Hey-1 which are transcriptional regulators associated with loss of differentiation. The aim of this study was to investigate the mechanism by which BMP-2 induces beta cell dysfunction and loss of cell maturity. Mouse islets exposed to BMP-2 for 10 days showed impaired glucose-stimulated insulin secretion and beta cell proliferation. BMP-2-induced beta cell dysfunction was associated with decreased expression of cell maturity and proliferation markers specific to the beta cell such as Ins1, Ucn3, and Ki67 and increased expression of Id1-4, Hes-1, and Hey-1. The top 30 most regulated proteins significantly correlated with corresponding mRNA expression. BMP-2-induced gene expression changes were associated with a predominant reduction in acetylation of H3K27 and a decrease in NeuroD1 chromatin binding activity. These results show that BMP-2 induces loss of beta cell maturity and suggest that remodeling of H3K27ac and decreased NeuroD1 DNA binding activity participate in the effect of BMP-2 on beta cell dysfunction.

Infection of Mouse Neural Progenitor Cells by Toxoplasma gondii Reduces Proliferation, Migration, and Neuronal Differentiation in Vitro

Congenital toxoplasmosis constitutes a major cause of pre- and postnatal complications. Fetal infection with Toxoplasma gondii influences development and can lead to microcephaly, encephalitis, and neurologic abnormalities. Systematic studies concerning the effects of neural progenitor cell infection with T. gondii are unavailable. Cortical intermediate progenitor cells cultivated as neurospheres obtained from E16.5 Swiss Webster mice were infected with T. gondii (ME49 strain) tachyzoites to mimic the developing mouse cerebral cortex in vitro. Infection was associated with decreased cell proliferation, detected by Ki-67 staining at 48 and 72 hours after infection in floating neurospheres, and reduced cellularity at 96 hours. Transient decreases in the expression of the neurogenesis-related transcription factors T-box brain protein 1, mouse atonal homolog protein 1, and hairy and enhancer of split protein 1 were found in infected cultures, while the level of transcription factor SOX-2 remained unaltered. Neurogenic potential, assessed in plated neurospheres, was impaired in infected cultures, as indicated by decreased late neuronal marker neurofilament heavy chain immunoreactivity. Infected cultures exhibited decreased overall migration rates at 48 and 120 hours. These findings indicate that T. gondii infection of neural progenitor cells may lead to reduced neurogenesis due to an imbalance in cell proliferation alongside an altered migratory profile. If translated to the in vivo situation, these data could explain, in part, cortical malformations in congenitally infected individuals.

Metamorphic gene regulation programs in Xenopus tropicalis tadpole brain

Amphibian metamorphosis is controlled by thyroid hormone (TH), which binds TH receptors (TRs) to regulate gene expression programs that underlie morphogenesis. Gene expression screens using tissues from premetamorphic tadpoles treated with TH identified some TH target genes, but few studies have analyzed genome-wide changes in gene regulation during spontaneous metamorphosis. We analyzed RNA sequencing data at four developmental stages from the beginning to the end of spontaneous metamorphosis, conducted on the neuroendocrine centers of Xenopus tropicalis tadpole brain. We also conducted chromatin immunoprecipitation sequencing (ChIP-seq) for TRs, and we compared gene expression changes during metamorphosis with those induced by exogenous TH. The mRNA levels of 26% of protein coding genes changed during metamorphosis; about half were upregulated and half downregulated. Twenty four percent of genes whose mRNA levels changed during metamorphosis had TR ChIP-seq peaks. Genes involved with neural cell differentiation, cell physiology, synaptogenesis and cell-cell signaling were upregulated, while genes involved with cell cycle, protein synthesis, and neural stem/progenitor cell homeostasis were downregulated. There is a shift from building neural structures early in the metamorphic process, to the differentiation and maturation of neural cells and neural signaling pathways characteristic of the adult frog brain. Only half of the genes modulated by treatment of premetamorphic tadpoles with TH for 16 h changed expression during metamorphosis; these represented 33% of the genes whose mRNA levels changed during metamorphosis. Taken together, our results provide a foundation for understanding the molecular basis for metamorphosis of tadpole brain, and they highlight potential caveats for interpreting gene regulation changes in premetamorphic tadpoles induced by exogenous TH.

Low-level repressive histone marks fine-tune gene transcription in neural stem cells

Coordinated regulation of gene activity by transcriptional and translational mechanisms poise stem cells for a timely cell-state transition during differentiation. Although important for all stemness-to-differentiation transitions, mechanistic understanding of the fine-tuning of gene transcription is lacking due to the compensatory effect of translational control. We used intermediate neural progenitor (INP) identity commitment to define the mechanisms that fine-tune stemness gene transcription in fly neural stem cells (neuroblasts). We demonstrate that the transcription factor FruitlessC (FruC) binds cis-regulatory elements of most genes uniquely transcribed in neuroblasts. Loss of fruC function alone has no effect on INP commitment but drives INP dedifferentiation when translational control is reduced. FruC negatively regulates gene expression by promoting low-level enrichment of the repressive histone mark H3K27me3 in gene cis-regulatory regions. Identical to fruC loss-of-function, reducing Polycomb Repressive Complex 2 activity increases stemness gene activity. We propose low-level H3K27me3 enrichment fine-tunes gene transcription in stem cells, a mechanism likely conserved from flies to humans.

The HDAC inhibitor domatinostat induces type I interferon α in Merkel cell carcinoma by HES1 repression

BACKGROUND

Class I selective histone deacetylase inhibitors (HDACi) have been previously demonstrated to not only increase major histocompatibility complex class I surface expression in Merkel cell carcinoma (MCC) cells by restoring the antigen processing and presentation machinery, but also exert anti-tumoral effect by inducing apoptosis. Both phenomena could be due to induction of type I interferons (IFN), as has been described for HDACi. However, the mechanism of IFN induction under HDACi is not fully understood because the expression of IFNs is regulated by both activating and inhibitory signaling pathways. Our own preliminary observations suggest that this may be caused by suppression of HES1.

METHODS

The effect of the class I selective HDACi domatinostat and IFNα on cell viability and the apoptosis of MCPyV-positive (WaGa, MKL-1) and -negative (UM-MCC 34) MCC cell lines, as well as, primary fibroblasts were assessed by colorimetric methods or measuring mitochondrial membrane potential and intracellular caspase-3/7, respectively. Next, the impact of domatinostat on IFNA and HES1 mRNA expression was measured by RT-qPCR; intracellular IFNα production was detected by flow cytometry. To confirm that the expression of IFNα induced by HDACi was due to the suppression of HES1, it was silenced by RNA interference and then mRNA expression of IFNA and IFN-stimulated genes was assessed.

RESULTS

Our studies show that the previously reported reduction in viability of MCC cell lines after inhibition of HDAC by domatinostat is accompanied by an increase in IFNα expression, both of mRNA and at the protein level. We confirmed that treatment of MCC cells with external IFNα inhibited their proliferation and induced apoptosis. Re-analysis of existing single-cell RNA sequencing data indicated that induction of IFNα by domatinostat occurs through repression of HES1, a transcriptional inhibitor of IFNA; this was confirmed by RT-qPCR. Finally, siRNA-mediated silencing of HES1 in the MCC cell line WaGa not only increased mRNA expression of IFNA and IFN-stimulated genes but also decreased cell viability.

CONCLUSION

Our results demonstrate that the direct anti-tumor effect of HDACi domatinostat on MCC cells is at least in part mediated via decreased HES1 expression allowing the induction of IFNα, which in turn causes apoptosis.

Targeting the transcription factor HES1 by L-menthol restores protein phosphatase 6 in keratinocytes in models of psoriasis

Protein Phosphatase 6 down-regulation in keratinocytes is a pivotal event that amplifies the inflammatory circuits in psoriasis, indicating that restoration of protein phosphatase 6 can be a rational strategy for psoriasis treatment. Through the phenotypic screen, we here identify L-menthol that ameliorates psoriasis-like skin inflammation by increasing protein phosphatase 6 in keratinocytes. Target identification approaches reveal an indispensable role for the transcription factor hairy and enhancer of split 1 in governing the protein phosphatase 6-upregulating function of L-menthol in keratinocytes. The transcription factor hairy and enhancer of split 1 is diminished in the epidermis of psoriasis patients and imiquimod-induced mouse model, while L-menthol upregulates the transcription factor hairy and enhancer of split 1 by preventing its proteasomal degradation. Mechanistically, the transcription factor hairy and enhancer of split 1 transcriptionally activates the expression of immunoglobulin-binding protein 1 which promotes protein phosphatase 6 expression and inhibits its ubiquitination. Collectively, we discover a therapeutic compound, L-menthol, for psoriasis, and uncover the dysfunctional the transcription factor hairy and enhancer of split 1- immunoglobulin-binding protein 1- protein phosphatase 6 axis that contributes to psoriasis pathology by using L-menthol as a probe.

Gut microbial sodium butyrate alleviates renal ischemia-reperfusion injury by regulating HES1/PPARα

This study investigated the effect of gut microbial sodium butyrate (NaB) on renal ischemia-reperfusion injury (IRI) and its mechanism using a rat model of renal IRI and a HK-2 cell model of hypoxia-reoxygenation (HR) injury. The activity of malondialdehyde, superoxide dismutase, glutathione peroxidase, and catalase in kidney tissues and HK-2 cells was detected. ELISA was performed to measure the concentrations of TNF-α, IL-1β, and IL-6 in serum and cell culture supernatant. TUNEL staining and flow cytometry were used to assess apoptosis in kidney tissues and HK-2 cells, respectively. UCSC and JASPAR predicted the binding sites between HES1 and PPARα promoter, followed by experimental verification of the binding. NaB pretreatment inhibited oxidative stress, inflammation, and apoptosis following renal IRI in vivo and in vitro. NaB suppressed the expression of HES1 and promoted that of PPARα. Overexpression of HES1 or knockdown of PPARα in HR-treated HK-2 cells inhibited the protective effects of NaB. HES1 repressed the expression of PPARα by binding PPARα promoter. In conclusion, NaB may alleviate renal IRI by promoting the transcription of PPARα via downregulation of HES1.

Induction of Transcriptional Inhibitor HES1 and the Related Repression of Tumor-Suppressor TXNIP Are Important Components of Cell-Transformation Program Imposed by Oncogenic Kinase NPM-ALK

This study reports that hairy and enhancer of split homolog-1 (HES1), known to repress gene transcription in progenitor cells of several cell lineages, was strongly expressed in cells and tissues of T-cell lymphoma expressing the oncogenic chimeric tyrosine kinase nucleophosmin (NPM)-anaplastic lymphoma kinase [ALK; ALK⁺ T-cell lymphoma (TCL)]. The structural analysis of the Orange domain of HES1 indicated that HES1 formed a highly stable homodimer. Of note, repression of HES1 expression led to inhibition of ALK⁺ TCL cell growth in vivo. The expression of the HES1 gene was induced by NPM-ALK through activation of STAT3, which bound to the gene's promoter and induced the gene's transcription. NPM-ALK also directly phosphorylated HES1 protein. In turn, HES1 up-regulated and down-regulated in ALK⁺ TCL cells, the expression of numerous genes, protein products of which are involved in key cell functions, such as cell proliferation and viability. Among the genes inhibited by HES1 was thioredoxin-interacting protein (TXNIP), encoding a protein implicated in promotion of cell death in various types of cells. Accordingly, ALK⁺ TCL cells and tissues lacked expression of TXNIP, and its transcription was co-inhibited by HES1 and STAT3 in an NPM-ALK-dependent manner. Finally, the induced expression of TXNIP induced massive apoptotic cell death of ALK⁺ TCL cells. The results reveal a novel NPM-ALK-controlled pro-oncogenic regulatory network and document an important role of HES and TXNIP in the NPM-ALK-driven oncogenesis, with the former protein displaying oncogenic and the latter tumor suppressor properties.

Differential phase register of Hes1 oscillations with mitoses underlies cell-cycle heterogeneity in ER+ breast cancer cells

Tumors exhibit heterogeneities that are not due to mutations, including cancer stem cells with different potencies. We show that the cancer stem-cell state predisposed to dormancy in vivo has a highly variable and long cell cycle. Using single-cell live imaging for the transcriptional repressor Hes1 (a key molecule in cancer), we show a type of circadian-like oscillatory expression of Hes1 in all cells in the population. The most potent cancer stem cells tend to divide around the trough of the Hes1 oscillatory wave, a feature predictive of a long cell cycle. A concept proposed here is that the position of cell division with respect to the Hes1 wave is predictive of its prospective cell-cycle length and cancer cellular substate.

Here, we study the dynamical expression of endogenously labeled Hes1, a transcriptional repressor implicated in controlling cell proliferation, to understand how cell-cycle length heterogeneity is generated in estrogen receptor (ER)⁺ breast cancer cells. We find that Hes1 shows oscillatory expression with ∼25 h periodicity and during each cell cycle has a variable peak in G1, a trough around G1–S transition, and a less variable second peak in G2/M. Compared to other subpopulations, the cell cycle in CD44^HighCD24^Low cancer stem cells is longest and most variable. Most cells divide around the peak of the Hes1 expression wave, but preceding mitoses in slow dividing CD44^HighCD24^Low cells appear phase-shifted, resulting in a late-onset Hes1 peak in G1. The position, duration, and shape of this peak, rather than the Hes1 expression levels, are good predictors of cell-cycle length. Diminishing Hes1 oscillations by enforcing sustained expression slows down the cell cycle, impairs proliferation, abolishes the dynamic expression of p21, and increases the percentage of CD44^HighCD24^Low cells. Reciprocally, blocking the cell cycle causes an elongation of Hes1 periodicity, suggesting a bidirectional interaction of the Hes1 oscillator and the cell cycle. We propose that Hes1 oscillations are functionally important for the efficient progression of the cell cycle and that the position of mitosis in relation to the Hes1 wave underlies cell-cycle length heterogeneity in cancer cell subpopulations.

Multiple functions of Hes genes in the proliferation and differentiation of neural stem cells

The HES proteins (hairy and Enhancer of split (E(spl)) homologs) are basic helix-loop-helix (bHLH) transcription factors that regulate the proliferation and differentiation of stem cells. Family members HES1, 3, and 5 are all critical regulators of nervous system development. The Hes genes exhibit oscillatory expression levels, and this dynamic expression allows for the complex regulation of numerous downstream genes such as Ascl1, Neurog2, Olig2 involved in the differentiation of specific cell types. In addition, HES proteins act as hubs for the molecule crosstalk among Notch, Wnt, and other signaling pathways that regulate nervous system development.

Inferring kinetic parameters of oscillatory gene regulation from single cell time-series data

Gene expression dynamics, such as stochastic oscillations and aperiodic fluctuations, have been associated with cell fate changes in multiple contexts, including development and cancer. Single cell live imaging of protein expression with endogenous reporters is widely used to observe such gene expression dynamics. However, the experimental investigation of regulatory mechanisms underlying the observed dynamics is challenging, since these mechanisms include complex interactions of multiple processes, including transcription, translation and protein degradation. Here, we present a Bayesian method to infer kinetic parameters of oscillatory gene expression regulation using an auto-negative feedback motif with delay. Specifically, we use a delay-adapted nonlinear Kalman filter within a Metropolis-adjusted Langevin algorithm to identify posterior probability distributions. Our method can be applied to time-series data on gene expression from single cells and is able to infer multiple parameters simultaneously. We apply it to published data on murine neural progenitor cells and show that it outperforms alternative methods. We further analyse how parameter uncertainty depends on the duration and time resolution of an imaging experiment, to make experimental design recommendations. This work demonstrates the utility of parameter inference on time course data from single cells and enables new studies on cell fate changes and population heterogeneity.

Hepatocyte TLR4 triggers inter-hepatocyte Jagged1/Notch signaling to determine NASH-induced fibrosis

Aberrant hepatocyte Notch activity is critical to the development of nonalcoholic steatohepatitis (NASH)-induced liver fibrosis, but mechanisms underlying Notch reactivation in developed liver are unclear. Here, we identified that increased expression of the Notch ligand Jagged1 (JAG1) tracked with Notch activation and nonalcoholic fatty liver disease (NAFLD) activity score (NAS) in human liver biopsy specimens and mouse NASH models. The increase in Jag1 was mediated by hepatocyte Toll-like receptor 4 (TLR4)-nuclear factor κB (NF-κB) signaling in pericentral hepatocytes. Hepatocyte-specific Jag1 overexpression exacerbated fibrosis in mice fed a high-fat diet or a NASH-provoking diet rich in palmitate, cholesterol, and sucrose and reversed the protection afforded by hepatocyte-specific TLR4 deletion, whereas hepatocyte-specific Jag1 knockout mice were protected from NASH-induced liver fibrosis. To test therapeutic potential of this biology, we designed a Jag1-directed antisense oligonucleotide (ASO) and a hepatocyte-specific N-acetylgalactosamine (GalNAc)-modified siRNA, both of which reduced NASH diet-induced liver fibrosis in mice. Overall, these data demonstrate that increased hepatocyte Jagged1 is the proximal hit for Notch-induced liver fibrosis in mice and suggest translational potential of Jagged1 inhibitors in patients with NASH.

Notch1 and Galectin-3 Modulate Cortical Reactive Astrocyte Response After Brain Injury

After a brain lesion, highly specialized cortical astrocytes react, supporting the closure or replacement of the damaged tissue, but fail to regulate neural plasticity. Growing evidence indicates that repair response leads astrocytes to reprogram, acquiring a partially restricted regenerative phenotype in vivo and neural stem cells (NSC) hallmarks in vitro. However, the molecular factors involved in astrocyte reactivity, the reparative response, and their relation to adult neurogenesis are poorly understood and remain an area of intense investigation in regenerative medicine. In this context, we addressed the role of Notch1 signaling and the effect of Galectin-3 (Gal3) as underlying molecular candidates involved in cortical astrocyte response to injury. Notch signaling is part of a specific neurogenic microenvironment that maintains NSC and neural progenitors, and Gal3 has a preferential spatial distribution across the cortex and has a central role in the proliferative capacity of reactive astrocytes. We report that in vitro scratch-reactivated cortical astrocytes from C57Bl/6J neonatal mice present nuclear Notch1 intracellular domain (NICD1), indicating Notch1 activation. Colocalization analysis revealed a subpopulation of reactive astrocytes at the lesion border with colocalized NICD1/Jagged1 complexes compared with astrocytes located far from the border. Moreover, we found that Gal3 increased intracellularly, in contrast to its extracellular localization in non-reactive astrocytes, and NICD1/Gal3 pattern distribution shifted from diffuse to vesicular upon astrocyte reactivation. In vitro, Gal3^–/– reactive astrocytes showed abolished Notch1 signaling at the lesion core. Notch1 receptor, its ligands (Jagged1 and Delta-like1), and Hes5 target gene were upregulated in C57Bl/6J reactive astrocytes, but not in Gal3^–/– reactive astrocytes. Finally, we report that Gal3^–/– mice submitted to a traumatic brain injury model in the somatosensory cortex presented a disrupted response characterized by the reduced number of GFAP reactive astrocytes, with smaller cell body perimeter and decreased NICD1 presence at the lesion core. These results suggest that Gal3 might be essential to the proper activation of Notch signaling, facilitating the cleavage of Notch1 and nuclear translocation of NICD1 into the nucleus of reactive cortical astrocytes. Additionally, we hypothesize that reactive astrocyte response could be dependent on Notch1/Jagged1-Hes5 signaling activation following brain injury.

Oscillations of Delta-like1 regulate the balance between differentiation and maintenance of muscle stem cells

Cell-cell interactions mediated by Notch are critical for the maintenance of skeletal muscle stem cells. However, dynamics, cellular source and identity of functional Notch ligands during expansion of the stem cell pool in muscle growth and regeneration remain poorly characterized. Here we demonstrate that oscillating Delta-like 1 (Dll1) produced by myogenic cells is an indispensable Notch ligand for self-renewal of muscle stem cells in mice. Dll1 expression is controlled by the Notch target Hes1 and the muscle regulatory factor MyoD. Consistent with our mathematical model, our experimental analyses show that Hes1 acts as the oscillatory pacemaker, whereas MyoD regulates robust Dll1 expression. Interfering with Dll1 oscillations without changing its overall expression level impairs self-renewal, resulting in premature differentiation of muscle stem cells during muscle growth and regeneration. We conclude that the oscillatory Dll1 input into Notch signaling ensures the equilibrium between self-renewal and differentiation in myogenic cell communities.

Activation of Notch3 in osteoblasts/osteocytes causes compartment-specific changes in bone remodeling

Notch receptors maintain skeletal homeostasis. NOTCH1 and 2 have been studied for their effects on bone remodeling. Although NOTCH3 plays a significant role in vascular physiology, knowledge about its function in other cellular environments, including bone, is limited. The present study was conducted to establish the function of NOTCH3 in skeletal cells using models of Notch3 misexpression. Microcomputed tomography demonstrated that Notch3 null mice did not have appreciable bone phenotypes. To study the effects of the NOTCH3 activation in the osteoblast lineage, BGLAP-Cre or Dmp1-Cre transgenics were crossed with RosaNotch3 mice, where the NOTCH3 intracellular domain is expressed following the removal of a loxP-flanked STOP cassette. Microcomputed tomography demonstrated that BGLAP-Cre;RosaNotch3 and Dmp1-Cre;RosaNotch3 mice of both sexes exhibited an increase in trabecular bone and in connectivity, with a decrease in cortical bone and increased cortical porosity. Histological analysis revealed a decrease in osteoclast number and bone resorption in trabecular bone and an increase in osteoclast number and void or pore area in cortical bone of RosaNotch3 mice. Bone formation was either decreased or could not be determined in Cre;RosaNotch3 mice. NOTCH3 activation in osteoblasts inhibited Alpl (alkaline phosphatase) and Bglap (osteocalcin) and induced Tnfsf11 (RANKL) and Tnfrsf11b (osteoprotegerin) mRNA, possibly explaining the trabecular bone phenotype. However, NOTCH3 induced Tnfsf11 and suppressed Tnfrsf11b in osteocytes, possibly explaining the cortical porosity. In conclusion, basal NOTCH3 is dispensable for skeletal homeostasis, whereas activation of NOTCH3 in osteoblasts/osteocytes inhibits osteoclastogenesis and bone resorption in cancellous bone but increases intracortical remodeling and causes cortical porosity.

Activation of the Notch signaling pathway in the anterior cingulate cortex is involved in the pathological process of neuropathic pain

Plastic changes in the anterior cingulate cortex (ACC) are critical in pain hypersensitivity caused by peripheral nerves injury. The Notch signaling pathway has been shown to regulate synaptic differentiation and transmission. Therefore, this study was to investigate the function of the Notch signaling pathway in the ACC during nociceptive transmission induced by neuropathic pain. We adopted Western blotting, N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT) microinjections, RNA interference targeting Notch1, Hairy and enhancer of split (Hes) 1 or Hes5, electrophysiological recordings, and behavioral tests to verify the link between Notch signaling in ACC and neuropathic pain with adult male Sprague-Dawley rats. Levels of the Notch intracellular domain were increased in ACC on day 7 after chronic constriction injury surgery or spared nerve injury. Meanwhile, the mRNA level of the downstream effector of Notch signaling Hes1 was increased, whereas the level of Hes5 mRNA did not change. Microinjection of DAPT, a γ-secretase (a key enzyme involved in Notch pathway) inhibitor, into ACC significantly reversed neuropathic pain behaviors. Intra-ACC injection of short hairpin RNA-Notch reduced Notch intracellular domain expression and decreased the potentiation of synaptic transmission in the ACC. Moreover, pain perceptions were also alleviated in rats subjected to chronic constriction injury or spared nerve injury. This process was mainly mediated by the downstream effector Hes1, but not Hes5. Based on these results, the activation of the Notch/Hes1 signaling pathway in the ACC participates in the development of neuropathic pain, indicating that the Notch pathway may be a new therapeutic target for treating chronic pain.

Non-classical 1p36 deletion in a patient with Duane retraction syndrome: case report and literature review

Background

Monosomy of 1p36 is considered the most common terminal microdeletion syndrome. It is characterized by intellectual disability, growth retardation, seizures, congenital anomalies, and distinctive facial features that are absent when the deletion is proximal, beyond the 1p36.32 region. In patients with proximal deletions, little is known about the associated phenotype, since only a few cases have been reported in the literature. Ocular manifestations in patients with classical 1p36 monosomy are frequent and include strabismus, myopia, hypermetropia, and nystagmus. However, as of today only one patient with 1p36 deletion and Duane retraction syndrome (DRS) has been reported.

Case presentation

We describe a patient with intellectual disability, facial dysmorphism, and bilateral Duane retraction syndrome (DRS) type 1. Array CGH showed a 7.2 Mb de novo deletion from 1p36.31 to 1p36.21.

Discussion

Our patient displayed DRS, which is not part of the classical phenotype and is not a common clinical feature in 1p36 deletion syndrome; we hypothesized that this could be associated with the overlapping deletion between the distal and proximal 1p36 regions. DRS is one of the Congenital Cranial Dysinnervation Disorders, and a genetic basis for the syndrome has been extensively reported. The HES3 gene is located at 1p36.31 and could be associated with oculomotor alterations, including DRS, since this gene is involved in the development of the 3rd cranial nerve and the 6th cranial nerve’s nucleus. We propose that oculomotor anomalies, including DRS, could be related to proximal 1p36 deletion, warranting a detailed ophthalmologic evaluation of these patients.

Neurogenesis From Neural Crest Cells: Molecular Mechanisms in the Formation of Cranial Nerves and Ganglia

The neural crest (NC) is a transient multipotent cell population that originates in the dorsal neural tube. Cells of the NC are highly migratory, as they travel considerable distances through the body to reach their final sites. Derivatives of the NC are neurons and glia of the peripheral nervous system (PNS) and the enteric nervous system as well as non-neural cells. Different signaling pathways triggered by Bone Morphogenetic Proteins (BMPs), Fibroblast Growth Factors (FGFs), Wnt proteins, Notch ligands, retinoic acid (RA), and Receptor Tyrosine Kinases (RTKs) participate in the processes of induction, specification, cell migration and neural differentiation of the NC. A specific set of signaling pathways and transcription factors are initially expressed in the neural plate border and then in the NC cell precursors to the formation of cranial nerves. The molecular mechanisms of control during embryonic development have been gradually elucidated, pointing to an important role of transcriptional regulators when neural differentiation occurs. However, some of these proteins have an important participation in malformations of the cranial portion and their mutation results in aberrant neurogenesis. This review aims to give an overview of the role of cell signaling and of the function of transcription factors involved in the specification of ganglia precursors and neurogenesis to form the NC-derived cranial nerves during organogenesis.

Unifying developmental programs for embryonic and postembryonic neurogenesis in the zebrafish retina

The zebrafish retina grows for a lifetime. Whether embryonic and postembryonic retinogenesis conform to the same developmental program is an outstanding question that remains under debate. Using single-cell RNA sequencing of ∼20,000 cells of the developing zebrafish retina at four different stages, we identified seven distinct developmental states. Each state explicitly expresses a gene set. Disruption of individual state-specific marker genes results in various defects ranging from small eyes to the loss of distinct retinal cell types. Using a similar approach, we further characterized the developmental states of postembryonic retinal stem cells (RSCs) and their progeny in the ciliary marginal zone. Expression pattern analysis of state-specific marker genes showed that the developmental states of postembryonic RSCs largely recapitulated those of their embryonic counterparts, except for some differences in rod photoreceptor genesis. Thus, our findings reveal the unifying developmental program used by the embryonic and postembryonic retinogenesis in zebrafish.

Krüppel homologue 1 interacts directly with Hairy and regulates ecdysis in the brown planthopper

Juvenile hormone (JH) plays important roles in the growth and development of insects. JH and its receptor methoprene-tolerant (Met) regulate the expression of transcription factors to control the transcription of downstream genes. The expression of Hairy (Hry) and Krüppel homologue 1 (Kr-h1) is regulated by JH and JH receptors. Hry and Kr-h1 are both crucial in mediating JH signalling. However, whether they interact at the gene level in regulating metamorphosis and whether they interact physically at the protein level remain unknown. We used co-immunoprecipitation, glutathione S-transferase pull-down and RNA interference (RNAi) approaches to study the genetic and biochemical interactions of the two proteins Hry and Kr-h1. The results showed that brown planthopper (Nilaparvata lugens) Hry and Kr-h1 interact directly: Hry binds to the N-terminal of Kr-h1, which includes five zinc-finger domains. The RNAi experiment showed that downregulation of Hry reduced the ratio of ecdysis failure caused by knockdown of Kr-h1, indicating that the downregulation of Hry might mitigate ecdysis failure via the downregulation of Kr-h1. The expression of Hry increased significantly when Kr-h1 was downregulated, whereas it did not change significantly when both were downregulated. Our results suggest that the binding of Hry protein with Kr-h1 prevents the N-terminal five zinc-finger domains from binding with DNA, which in turn inactivates the transcription activator or inhibitor function of Kr-h1. Hry could possibly be used as a target for pesticide applications in the future.

Methylation deficiency disrupts biological rhythms from bacteria to humans

The methyl cycle is a universal metabolic pathway providing methyl groups for the methylation of nuclei acids and proteins, regulating all aspects of cellular physiology. We have previously shown that methyl cycle inhibition in mammals strongly affects circadian rhythms. Since the methyl cycle and circadian clocks have evolved early during evolution and operate in organisms across the tree of life, we sought to determine whether the link between the two is also conserved. Here, we show that methyl cycle inhibition affects biological rhythms in species ranging from unicellular algae to humans, separated by more than 1 billion years of evolution. In contrast, the cyanobacterial clock is resistant to methyl cycle inhibition, although we demonstrate that methylations themselves regulate circadian rhythms in this organism. Mammalian cells with a rewired bacteria-like methyl cycle are protected, like cyanobacteria, from methyl cycle inhibition, providing interesting new possibilities for the treatment of methylation deficiencies.

Fustin et al. reveal the evolutionarily conserved link between methyl metabolism and biological clocks. This study suggests the possibility of translating fundamental understanding of methylation deficiencies to clinical applications.

Whitefly HES1 binds to the intergenic region of Tomato yellow leaf curl China virus and promotes viral gene transcription

Intergenic region of begomovirus genome is vital to virus replication and viral gene transcription in plants. Previous studies have reported that Tomato yellow leaf curl China virus (TYLCCNV), a begomovirus, is able to accumulate and transcribe in its whitefly vector. However, the viral and host components that participate in begomovirus transcription in whiteflies are hitherto unknown. Using a yeast one-hybrid system, we identified >50 whitefly proteins that interacted with TYLCCNV intergenic region. Dual luciferase analysis revealed that one of the identified proteins, the hairy and enhancer of split homolog-1 (HES1), specifically bound to CACGTG motif in TYLCCNV intergenic region. Silencing HES1 decreased viral transcription, accumulation and transmission. These results demonstrate that the interactions between whitefly proteins and the intergenic region of TYLCCNV may contribute to viral transcription in the whitefly vector. Our findings offer valuable clues for the research and development of novel strategies to interfere with begomovirus transmission.

Class C1 decoy oligodeoxynucleotide inhibits profibrotic genes expression in rat hepatic stellate cells

The aim of the present study was to investigate whether class C1 decoy oligodeoxynucleotides (ODNs) can inhibit the expression of pro‑fibrotic genes associated with rat hepatic stellate cell (HSC) activation and hepatic fibrosis. Luciferase reporter assays were performed to test the promoter activities of transforming growth factor (TGF)‑β and its downstream target genes following transfection of decoy ODNs and plasmids into HSC‑T6 cells, and western blot assays were performed to measure the protein expression of those genes following decoy ODN transfection. Class C1 decoy ODNs were confirmed to inhibit the promoter activity of TGF‑β and its downstream target genes, such as type 1 collagen (COLI)α1, tissue inhibitor of metalloproteinases (TIMP)1 and α‑smooth muscle actin by Gaussia luciferase reporter assay, and to further downregulate the expression of TGF‑β, SMAD3, COLIα1 and TIMP1 by western blotting in activated HSC‑T6 cells. In conclusion, class C1 decoy ODNs inhibited pro‑fibrotic gene expression in rat HSCS by downregulating TGF‑β signaling.

Noise in the Vertebrate Segmentation Clock Is Boosted by Time Delays but Tamed by Notch Signaling

Taming cell-to-cell variability in gene expression is critical for precise pattern formation during embryonic development. To investigate the source and buffering mechanism of expression variability, we studied a biological clock, the vertebrate segmentation clock, controlling the precise spatiotemporal patterning of the vertebral column. By counting single transcripts of segmentation clock genes in zebrafish, we show that clock genes have low RNA amplitudes and expression variability is primarily driven by gene extrinsic sources, which is suppressed by Notch signaling. We further show that expression noise surprisingly increases from the posterior progenitor zone to the anterior segmentation and differentiation zone. Our computational model reproduces the spatial noise profile by incorporating spatially increasing time delays in gene expression. Our results, suggesting that expression variability is controlled by the balance of time delays and cell signaling in a vertebrate tissue, will shed light on the accuracy of natural clocks in multi-cellular systems and inspire engineering of robust synthetic oscillators.

Synergistic repression of thyroid hyperplasia by cyclin C and Pten

The cyclin C-Cdk8 kinase has been identified as both a tumor suppressor and an oncogene depending on the cell type. The genomic locus encoding cyclin C (Ccnc) is often deleted in aggressive anaplastic thyroid tumors. To test for a potential tumor suppressor role for cyclin C, Ccnc alone, or Ccnc in combination with a previously described thyroid tumor suppressor Pten, was deleted late in thyroid development. Although mice harboring individual Pten or Ccnc deletions exhibited modest thyroid hyperplasia, the double mutant demonstrated dramatic thyroid expansion resulting in animal death by 22 weeks. Further analysis revealed that Ccnc^thyr-/- tissues exhibited a reduction in signal transducer and activator of transcription 3 (Stat3) phosphorylation at Ser727. Further analysis uncovered a post-transcriptional requirement of both Pten and cyclin C in maintaining the levels of the p21 and p53 tumor suppressors (also known as CDKN1A and TP53, respectively) in thyroid tissue. In conclusion, these data reveal the first tumor suppressor role for cyclin C in a solid tumor model. In addition, this study uncovers new synergistic activities of Pten and cyclin C to promote quiescence through maintenance of p21 and p53.

Development and epigenetic plasticity of murine Müller glia

The ability to regenerate the entire retina and restore lost sight after injury is found in some species and relies mostly on the epigenetic plasticity of Müller glia. To understand the role of mammalian Müller glia as a source of progenitors for retinal regeneration, we investigated changes in gene expression during differentiation of retinal progenitor cells (RPCs) into Müller glia and analyzed the global epigenetic profile of adult Müller glia. We observed significant changes in gene expression during differentiation of RPCs into Müller glia in only a small group of genes and found a high similarity between RPCs and Müller glia on the transcriptomic and epigenomic levels. Our findings also indicate that Müller glia are epigenetically very close to late-born retinal neurons, but not early-born retinal neurons. Importantly, we found that key genes required for phototransduction were highly methylated. Thus, our data suggest that Müller glia are epigenetically very similar to late RPCs; however, obstacles for regeneration of the entire mammalian retina from Müller glia may consist of repressive chromatin and highly methylated DNA in the promoter regions of many genes required for the development of early-born retinal neurons. In addition, DNA demethylation may be required for proper reprogramming and differentiation of Müller glia into rod photoreceptors.

An antibody to Notch3 reverses the skeletal phenotype of lateral meningocele syndrome in male mice

Lateral meningocele syndrome (LMS), a genetic disorder characterized by meningoceles and skeletal abnormalities, is associated with NOTCH3 mutations. We created a mouse model of LMS (Notch3^tm1.1Ecan ) by introducing a tandem termination codon in the Notch3 locus upstream of the proline (P), glutamic acid (E), serine (S) and threonine (T) domain. Microcomputed tomography demonstrated that Notch3^tm1.1Ecan mice exhibit osteopenia. The cancellous bone osteopenia was no longer observed after the intraperitoneal administration of antibodies directed to the negative regulatory region (NRR) of Notch3. The anti-Notch3 NRR antibody suppressed the expression of Hes1, Hey1, and Hey2 (Notch target genes), and decreased Tnfsf11 (receptor activator of NF Kappa B ligand) messenger RNA in Notch3^tm1.1Ecan osteoblast (OB) cultures. Bone marrow-derived macrophages (BMMs) from Notch3^tm1.1Ecan mutants exhibited enhanced osteoclastogenesis in culture, and this was increased in cocultures with Notch3^tm1.1Ecan OB. Osteoclastogenesis was suppressed by anti-Notch3 NRR antibodies in Notch3^tm1.1Ecan OB/BMM cocultures. In conclusion, the cancellous bone osteopenia of Notch3^tm1.1Ecan mutants is reversed by anti-Notch3 NRR antibodies.

Hes1 attenuates type I IFN responses via VEGF-C and WDFY1

Transcription factor Hes1 acts as a homeostatic negative regulator of type I interferon production to restrain interferon-mediated immune responses, including antiviral immunity and autoimmune conditions. Mechanistically, Hes1 suppresses interferon expression by targeting a regulatory circuit composed of WDFY1 and VEGF-C.

Induction of type I interferons (IFNs) is critical for eliciting competent immune responses, especially antiviral immunity. However, uncontrolled IFN production contributes to pathogenesis of autoimmune and inflammatory diseases. We found that transcription factor Hes1 suppressed production of type I IFNs and expression of IFN-stimulated genes. Functionally, Hes1-deficient mice displayed a heightened IFN signature in vivo, mounted enhanced resistance against encephalomyocarditis virus infection, and showed signs of exacerbated experimental lupus nephritis. Mechanistically, Hes1 did not suppress IFNs via direct transcriptional repression of IFN-encoding genes. Instead, Hes1 attenuated activation of TLR upstream signaling by inhibition of an adaptor molecule, WDFY1. Genome-wide assessment of Hes1 occupancy revealed that suppression of WDFY1 was secondary to direct binding and thus enhancement of expression of VEGF-C by Hes1, making Vegfc a rare example of an Hes1 positively regulated gene. In summary, these results identified Hes1 as a homeostatic negative regulator of type I IFNs for the maintenance of immune balance in the context of antiviral immunity and autoimmune diseases.

Single cell RNA-sequencing identified Dec2 as a suppressive factor for spermatogonial differentiation by inhibiting Sohlh1 expression

Gonocyte-to-spermatogonia transition is a critical fate determination process to initiate sperm production throughout the lifecycle. However, the molecular dynamics of this process has not been fully elucidated mainly due to the asynchronized differentiation stages of neonatal germ cells. In this study, we employed single cell RNA sequencing analyses of P1.5–5.5 germ cells to clarify the temporal dynamics of gene expression during gonocyte-to-spermatogonia transition. The analyses identified transcriptional modules, one of which regulates spermatogonial gene network in neonatal germ cells. Among them, we identified Dec2, a bHLH-type transcription factor, as a transcriptional repressor for a spermatogonial differentiation factor Sohlh1. Deficiency of Dec2 in mice induces significant reduction of undifferentiated spermatogonia, and transplantation assay using Dec2-depleted cells also demonstrated the impaired efficiency of engraftment, suggesting its role in maintaining spermatogonial stem cells (SSCs). Collectively, this study revealed the intrinsic role of a new SSC factor Dec2, which protects germ cells from inadequate differentiation during neonatal testis development.

A pivotal role of androgen signaling in Notch-responsive cells in prostate development, maturation, and regeneration

Androgen signaling is essential for prostate development, morphogenesis, and regeneration. Emerging evidence also indicates a regulatory role of Notch signaling in prostate development, differentiation, and growth. However, the collaborative regulatory mechanisms of androgen and Notch signaling during prostate development, growth, and regeneration are largely unknown. Hairy and Enhancer of Split 1 (Hes1) is a transcriptional regulator of Notch signaling pathways, and its expression is responsive to Notch signaling. Hes1-expressing cells have been shown to possess the regenerative capability to repopulate a variety of adult tissues. In this study, we developed new mouse models to directly assess the role of the androgen receptor in prostatic Hes1-expressing cells. Selective deletion of AR expression in embryonic Hes1-expressing cells impeded early prostate development both in vivo and in tissue xenograft experiments. Prepubescent deletion of AR expression in Hes1-expressing cells resulted in prostate glands containing abnormalities in cell morphology and gland architecture. A population of castration-resistant Hes1-expressing cells was revealed in the adult prostate, with the ability to repopulate prostate epithelium following androgen supplementation. Deletion of AR in Hes1-expressing cells diminishes their regenerative ability. These lines of evidence demonstrate a critical role for the AR in Notch-responsive cells during the course of prostate development, morphogenesis, and regeneration, and implicate a mechanism underlying interaction between the androgen and Notch signaling pathways in the mouse prostate.

Non-canonical cholinergic anti-inflammatory pathway-mediated activation of peritoneal macrophages induces Hes1 and blocks ischemia/reperfusion injury in the kidney

The cholinergic anti-inflammatory pathway (CAP) links the nervous and immune systems and modulates innate and adaptive immunity. Activation of the CAP by vagus nerve stimulation exerts protective effects in a wide variety of clinical disorders including rheumatoid arthritis and Crohn's disease, and in murine models of acute kidney injury including ischemia/reperfusion injury (IRI). The canonical CAP pathway involves activation of splenic alpha7-nicotinic acetylcholine receptor (α7nAChR)-positive macrophages by splenic β2-adrenergic receptor-positive CD4+ T cells. Here we demonstrate that ultrasound or vagus nerve stimulation also activated α7nAChR-positive peritoneal macrophages, and that adoptive transfer of these activated peritoneal macrophages reduced IRI in recipient mice. The protective effect required α7nAChR, and did not occur in splenectomized mice or in mice lacking T and B cells, suggesting a bidirectional interaction between α7nAChR-positive peritoneal macrophages and other immune cells including β2-adrenergic receptor-positive CD4+ T cells. We also found that expression of hairy and enhancer of split-1 (Hes1), a basic helix-loop-helix DNA-binding protein, is induced in peritoneal macrophages by ultrasound or vagus nerve stimulation. Adoptive transfer of Hes1-overexpressing peritoneal macrophages reduced kidney IRI. Our data suggest that Hes1 is downstream of α7nAChR and is important to fully activate the CAP. Taken together, these results suggest that peritoneal macrophages play a previously unrecognized role in mediating the protective effect of CAP activation in kidney injury, and that Hes1 is a new candidate pharmacological target to activate the CAP.

Olfactory receptor 43 reduces hepatic lipid accumulation and adiposity in mice

Olfactory receptors are primarily expressed in nasal olfactory epithelium, but these receptors are also ectopically expressed in diverse tissues. In this study, we investigated the biological functions of Olfr43, a mouse homolog of human OR1A1, in cultured hepatocytes and mice to assess its functionality in lipid metabolism. Olfr43 was expressed in mouse hepatocytes, and Olfr43 activation by a known ligand, (-)-carvone, stimulated cAMP response element-binding protein (CREB) activity. In ligand-receptor binding studies using site-directed mutagenesis, (-)-carvone binding required two residues, M257 and Y258, in Olfr43. In the mouse study, oral administration of (-)-carvone for 5 weeks in high-fat diet-fed mice improved energy metabolism, including reductions in hepatic steatosis and adiposity, and improved glucose and insulin tolerance. In mouse livers and cultured mouse hepatocytes, Olfr43 activation simulated the CREB-hairy and enhancer of split 1 (HES1)-peroxisome proliferator-activated receptor (PPAR)-γ signaling axis, leading to a reduction in hepatic triglyceride accumulation in the mouse liver. Thus, long-term administration of (-)-carvone reduces hepatic steatosis. The knockdown of Olfr43 gene expression in cultured hepatocytes negated these effects of (-)-carvone. In conclusion, an ectopic olfactory receptor, hepatic Olfr43, regulates energy metabolism via the CREB-HES1-PPARγ signaling axis.

The Absence of TLR4 Prevents Fetal Brain Injury in the Setting of Intrauterine Inflammation

BACKGROUND

Exposure to intrauterine inflammation during pregnancy is linked to brain injury and neurobehavioral disorders in affected children. Innate immunity, specifically Toll-like receptor (TLR) signaling pathways are present throughout the reproductive tract as well as in the placenta, fetal membranes, and fetus. The TLR pathways are mechanistically involved in host responses to foreign pathogens and may lead to brain injury associated with prenatal inflammation.

OBJECTIVE

We aimed to determine whether the activation of the TLR4 signaling pathway, in the mother and fetus, is critical to fetal brain injury in the setting of intrauterine inflammation.

METHODS

A mini-laparotomy was performed on time pregnant C57B6 mice and 2 knockout mouse strains lacking the function of the Tlr4 and Myd88 genes on embryonic day 15. Intrauterine injections of Escherichia coli lipopolysaccharide or saline were administered as described previously. Dams were killed 6 hours postsurgery, and placental, amniotic fluid, and fetal brain tissue were collected. To assess brain injury, quantitative polymerase chain reaction (qPCR) analysis was performed on multiple components of the NOTCH signaling pathway, including Hes genes. Interleukin (IL) IL6, IL1β, and CCL5 expression was assessed using qPCR and enzyme-linked immunosorbent assay.

RESULTS

Using an established mouse model of intrauterine inflammation, we demonstrate that the abrogation of TLR4 signaling eliminates the cytokine response in mother and fetus and prevents brain injury associated with increased expression of transcriptional effectors of the NOTCH signaling pathway, Hes1 and Hes5.

CONCLUSIONS

These data show that the activation of the TLR4 signaling pathway is necessary for the development of fetal brain injury in response to intrauterine inflammation.

Multilayered gene control drives timely exit from the stem cell state in uncommitted progenitors during Drosophila asymmetric neural stem cell division

Self-renewal genes maintain stem cells in an undifferentiated state by preventing the commitment to differentiate. Robust inactivation of self-renewal gene activity following asymmetric stem cell division allows uncommitted stem cell progeny to exit from an undifferentiated state and initiate the commitment to differentiate. Nonetheless, how self-renewal gene activity at mRNA and protein levels becomes synchronously terminated in uncommitted stem cell progeny is unclear. We demonstrate that a multilayered gene regulation system terminates self-renewal gene activity at all levels in uncommitted stem cell progeny in the fly neural stem cell lineage. We found that the RNA-binding protein Brain tumor (Brat) targets the transcripts of a self-renewal gene, deadpan (dpn), for decay by recruiting the deadenylation machinery to the 3' untranslated region (UTR). Furthermore, we identified a nuclear protein, Insensible, that complements Cullin-mediated proteolysis to robustly inactivate Dpn activity by limiting the level of active Dpn through protein sequestration. The synergy between post-transcriptional and transcriptional control of self-renewal genes drives timely exit from the stem cell state in uncommitted progenitors. Our proposed multilayered gene regulation system could be broadly applicable to the control of exit from stemness in all stem cell lineages.

Loss of Canonical Notch Signaling Affects Multiple Steps in NK Cell Development in Mice

Within the hematopoietic system, the Notch pathway is critical for promoting thymic T cell development and suppressing the B and myeloid lineage fates; however, its impact on NK lymphopoiesis is less understood. To study the role of Notch during NK cell development in vivo, we investigated different NK cell compartments and function in Rbp-Jk^fl/flVav-Cre^tg/+ mice, in which Rbp-Jk, the major transcriptional effector of canonical Notch signaling, was specifically deleted in all hematopoietic cells. Peripheral conventional cytotoxic NK cells in Rbp-Jk-deleted mice were significantly reduced and had an activated phenotype. Furthermore, the pool of early NK cell progenitors in the bone marrow was decreased, whereas immature NK cells were increased, leading to a block in NK cell maturation. These changes were cell intrinsic as the hematopoietic chimeras generated after transplantation of Rbp-Jk-deficient bone marrow cells had the same NK cell phenotype as the Rbp-Jk-deleted donor mice, whereas the wild-type competitors did not. The expression of several crucial NK cell regulatory pathways was significantly altered after Rbp-Jk deletion. Together, these results demonstrate the involvement of canonical Notch signaling in regulation of multiple stages of NK cell development.

The b-HLH transcription factor Hes3 participates in neural plate border formation by interfering with Wnt/β-catenin signaling

Hes3 belongs to the Hes basic helix-loop-helix family of transcriptional repressors that play central roles in maintaining progenitor cells and regulating binary cell fate decisions in the embryo. During Xenopus laevis development, hes3 is expressed in the embryonic ectoderm in a horseshoe shape domain at the edge of the developing neural pate. Hes3 mis-expression at early neurula stage blocks neural crest (snai2, sox8, sox9 and sox10) and cranial placode (six1 and dmrta1) gene expression, and promotes neural plate (sox2 and sox3) fate. At tailbud stage, these embryos exhibited a massive up-regulation of both sox8 and sox10 expression, associated with an increase in genes important for melanocytes differentiation (mitf and dct). Using a hormone inducible construct we show that Hes3 does not induce a pigment cell differentiation program de novo, rather it maintains progenitor cells in an undifferentiated state, and as Hes3 expression subsides overtime these cells adopt a pigment cell fate. We demonstrate that mechanistically Hes3 mediates its activity through inhibition of Wnt/β-catenin signaling, a molecular pathway critical for neural crest specification and pigment cell lineage differentiation. We propose that Hes3 at the edge of the neural plate spatially restricts the response to mesoderm-derived Wnt ligands, thereby contributing to the establishment of sharp boundaries of gene expression at the neural plate border.

Deregulation of the Notch pathway as a common road in viral carcinogenesis

The Notch pathway is a conserved signaling pathway and a form of direct cell-cell communication related to many biological processes during development and adulthood. Deregulation of the Notch pathway is involved in many diseases, including cancer. Almost 20% of all cancer cases have an infectious etiology, with viruses responsible for at least 1.5 million new cancer cases per year. Seven groups of viruses have been classified as oncogenic: hepatitis B and C viruses (HBV and HCV respectively), Epstein-Barr virus (EBV), Kaposi sarcoma-associated herpesvirus (KSHV), human T lymphotropic virus (HTLV-1), human papillomavirus (HPV), and Merkel cell polyomavirus (MCPyV). These viruses share the ability to manipulate a variety of cell pathways that are critical in proliferation and differentiation, leading to malignant transformation. Viral proteins interact directly or indirectly with different members of the Notch pathway, altering their normal function. This review focuses exclusively on the direct interactions of viral oncoproteins with Notch elements, providing a deeper understanding of the dual behavior of the Notch pathway as activator or suppressor of neoplasia in virus-related cancers.

Epithelial Hes1 maintains gut homeostasis by preventing microbial dysbiosis

Recent advancements suggest that in addition to its roles in developmental processes, transcription repressor hairy and enhancer of split 1 (Hes1) also acts as a key regulator of inflammatory responses. A healthy gut microbiota ecology is critical for establishment of tissue homeostasis. However, the role of epithelial Hes1 in regulating intestinal microbiota ecology and intestinal homeostasis remains unexplored. Here we show that epithelial Hes1 deficiency leads to intestinal microbial dysbiosis and disturbed homeostasis. Both inducible Hes1 deletion and intestinal epithelial cell (IEC)-intrinsic Hes1 deletion resulted in loss of Bacteroidetes in ileum and increase of Escherichia coli and Akkermansia muciniphila in colon. Loss of Bacteroidetes closely correlated with decreased expression of commensal-dependent antimicrobial genes, leading to impaired resistance against pathogenic bacterial colonization. Moreover, Hes1 deficiency enhanced susceptibility to Dextran sodium sulphate-induced intestinal inflammation. Of note, transfer of Hes1-deficient-mouse-derived fecal microbiota promoted intestinal inflammation. The increase of A. muciniphila in colon was associated with Hes1-deficiency-induced unbalanced mucosal microhabitats. Thus, our results support that IEC-intrinsic Hes1 maintains gut homeostasis by preventing microbial dysbiosis partially through regulating mucosal microhabitats.

Hairy and enhancer of split 1 (HES1) protects cells from endoplasmic reticulum stress-induced apoptosis through repression of

Disruption in endoplasmic reticulum (ER) function, termed ER stress, occurs in many diseases, including neurodegenerative disorders, diabetes, and cancer. Cells respond to ER stress with the unfolded protein response (UPR), which triggers a broad transcriptional program to restore and enhance ER function. Here, we found that ER stress up-regulates the mRNA encoding the developmentally regulated transcriptional repressor hairy and enhancer of split 1 (HES1), in a variety cell types. Depletion of HES1 increased cell death in response to ER stress in mouse and human cells, in a manner that depended on the pro-apoptotic gene growth arrest and DNA damage-inducible protein GADD34 (also known as Protein phosphatase 1 regulatory subunit 15A, or MyD116). Furthermore, HES1 bound to the GADD34 promoter, and its depletion led to an up-regulation of GADD34 expression during ER stress. Our results identify HES1 as a repressor of GADD34 expression, and reveal that HES1 contributes to cell fate determination in response to ER stress.

Dynamic Ligand Discrimination in the Notch Signaling Pathway

The Notch signaling pathway comprises multiple ligands that are used in distinct biological contexts. In principle, different ligands could activate distinct target programs in signal-receiving cells, but it is unclear how such ligand discrimination could occur. Here, we show that cells use dynamics to discriminate signaling by the ligands Dll1 and Dll4 through the Notch1 receptor. Quantitative single-cell imaging revealed that Dll1 activates Notch1 in discrete, frequency-modulated pulses that specifically upregulate the Notch target gene Hes1. By contrast, Dll4 activates Notch1 in a sustained, amplitude-modulated manner that predominantly upregulates Hey1 and HeyL. Ectopic expression of Dll1 or Dll4 in chick neural crest produced opposite effects on myogenic differentiation, showing that ligand discrimination can occur in vivo. Finally, analysis of chimeric ligands suggests that ligand-receptor clustering underlies dynamic encoding of ligand identity. The ability of the pathway to utilize ligands as distinct communication channels has implications for diverse Notch-dependent processes.

Peripheral administration of lactate produces antidepressant-like effects

In addition to its role as metabolic substrate that can sustain neuronal function and viability, emerging evidence supports a role for l-lactate as an intercellular signaling molecule involved in synaptic plasticity. Clinical and basic research studies have shown that major depression and chronic stress are associated with alterations in structural and functional plasticity. These findings led us to investigate the role of l-lactate as a potential novel antidepressant. Here we show that peripheral administration of l-lactate produces antidepressant-like effects in different animal models of depression that respond to acute and chronic antidepressant treatment. The antidepressant-like effects of l-lactate are associated with increases in hippocampal lactate levels and with changes in the expression of target genes involved in serotonin receptor trafficking, astrocyte functions, neurogenesis, nitric oxide synthesis and cAMP signaling. Further elucidation of the mechanisms underlying the antidepressant effects of l-lactate may help to identify novel therapeutic targets for the treatment of depression.