DLK1 and DLK2, two non-canonical ligands of NOTCH receptors, differentially modulate the osteogenic differentiation of mesenchymal C3H10T1/2 cells.

Background: C3H10T1/2 is a mesenchymal cell line capable of differentiating into osteoblasts, adipocytes and chondrocytes. The differentiation of these cells into osteoblasts is modulated by various transcription factors, such as RUNX2. Additionally, several interconnected signaling pathways, including the NOTCH pathway, play a crucial role in modulating their differentiation into mature bone cells.

Pericardial delta like non-canonical NOTCH ligand 1 (Dlk1) augments fibrosis in the heart through epithelial to mesenchymal transition.

Background: Heart failure due to myocardial infarction (MI) involves fibrosis driven by epicardium-derived cells (EPDCs) and cardiac fibroblasts, but strategies to inhibit and provide cardio-protection remains poor. The imprinted gene, non-canonical NOTCH ligand 1 (Dlk1), has previously been shown to mediate fibrosis in the skin, lung and liver, but very little is known on its effect in the heart.

Methods: Herein, human pericardial fluid/plasma and tissue biopsies were assessed for DLK1, whereas the spatiotemporal expression of Dlk1 was determined in mouse hearts.

Different Expression Levels of DLK2 Inhibit NOTCH Signaling and Inversely Modulate MDA-MB-231 Breast Cancer Tumor Growth In Vivo.

NOTCH signaling is implicated in the development of breast cancer tumors. DLK2, a non-canonical inhibitor of NOTCH signaling, was previously shown to be involved in skin and breast cancer. In this work, we studied whether different levels of DLK2 expression influenced the breast cancer characteristics of MDA-MB-231 cells.

NOTCH4 Exhibits Anti-Inflammatory Activity in Activated Macrophages by Interfering With Interferon-γ and TLR4 Signaling.

NOTCH4 is a member of the NOTCH family of receptors whose expression is intensively induced in macrophages after their activation by Toll-like receptors (TLR) and/or interferon-γ (IFN-γ). In this work, we show that this receptor acts as a negative regulator of macrophage activation by diminishing the expression of proinflammatory cytokines, such as IL-6 and IL-12, and costimulatory proteins, such as CD80 and CD86. We have observed that NOTCH4 inhibits IFN-γ signaling by interfering with STAT1-dependent transcription.

Stromal DLK1 promotes proliferation and inhibits differentiation of the intestinal epithelium during development.

The stem/progenitor cells of the developing intestine are biologically distinct from their adult counterparts. Here, we examine the microenvironmental cues that regulate the embryonic stem/progenitor population, focusing on the role of Notch pathway factor delta-like protein-1 (DLK1). mRNA-seq analyses of intestinal mesenchymal cells (IMCs) collected from embryonic day 14.

Deletion of delta-like 1 homologue accelerates renal inflammation by modulating the Th17 immune response.

Preclinical studies have demonstrated that activation of the NOTCH pathway plays a key role in the pathogenesis of kidney damage. There is currently no information on the role of the Delta-like homologue 1 (DLK1), a NOTCH inhibitor, in the regulation of renal damage. Here, we investigated the contribution of DLK1 to experimental renal damage and the underlying molecular mechanisms.

NOTCH3 signaling is essential for NF-κB activation in TLR-activated macrophages.

Macrophage activation by Toll receptors is an essential event in the development of the response against pathogens. NOTCH signaling pathway is involved in the control of macrophage activation and the inflammatory processes. In this work, we have characterized NOTCH signaling in macrophages activated by Toll-like receptor (TLR) triggering and determined that DLL1 and DLL4 are the main ligands responsible for NOTCH signaling.

NOTCH Receptors and DLK Proteins Enhance Brown Adipogenesis in Mesenchymal C3H10T1/2 Cells.

The NOTCH family of receptors and ligands is involved in numerous cell differentiation processes, including adipogenesis. We recently showed that overexpression of each of the four NOTCH receptors in 3T3-L1 preadipocytes enhances adipogenesis and modulates the acquisition of the mature adipocyte phenotype. We also revealed that DLK proteins modulate the adipogenesis of 3T3-L1 preadipocytes and mesenchymal C3H10T1/2 cells in an opposite way, despite their function as non-canonical inhibitory ligands of NOTCH receptors.

The imprinted gene Delta like non-canonical notch ligand 1 (Dlk1) associates with obesity and triggers insulin resistance through inhibition of skeletal muscle glucose uptake.

Background: The imprinted gene Delta like non-canonical Notch ligand 1 (Dlk1) is considered an inhibitor of adipogenesis, but its in vivo impact on fat mass indeed remains elusive and controversial.

Methods: Fat deposits were assessed by MRI and DXA scanning in two cohorts of non-diabetic men, whereas glucose disposal rate (GDR) was determined during euglycemic hyperinsulinemic clamp. Blood analyte measurements were used for correlation and mediation analysis to investigate how age, BMI, and fat percentage affect the relation between DLK1 and GDR.

Author Correction: DLK proteins modulate NOTCH signaling to influence a brown or white 3T3-L1 adipocyte fate.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

DLK proteins modulate NOTCH signaling to influence a brown or white 3T3-L1 adipocyte fate.

The role of NOTCH signaling in adipogenesis is highly controversial, with data indicating null, positive or negative effects on this differentiation process. We hypothesize that these contradictory results could be due to the different global NOTCH signaling levels obtained in different experimental settings, because of a specific modulation of NOTCH receptors' activity by their ligands. We have previously demonstrated that DLK1 and DLK2, two non-canonical NOTCH1 ligands that inhibit NOTCH1 signaling in a dose-dependent manner, modulate the adipogenesis process of 3T3-L1 preadipocytes.

Deletion of Dlk1 increases the vulnerability to developing anxiety-like behaviors and ethanol consumption in mice.

Anxiety and alcohol use disorders (AUD) often present together, constituting a significant public health problem worldwide. In this study, we investigated the role of DLK1, a ligand of the Delta/NOTCH epidermal growth factor (EGF)-like protein family, reported to play a role in DA neurons differentiation in the striatum, as a neurobiological factor involved in the mechanisms regulating this psychiatric comorbidity. We exposed Dlk1 knockout mice (Dlk1-/- mice) to the open-field (OF), the light-dark box (LBD) and the elevated plus maze (EPM) tests, evaluating motivation to drink and ethanol consumption using the oral ethanol self-administration (OEA) paradigm.

Deletion of delta-like 1 homologue accelerates fibroblast-myofibroblast differentiation and induces myocardial fibrosis.

Aims: Myocardial fibrosis is associated with profound changes in ventricular architecture and geometry, resulting in diminished cardiac function. There is currently no information on the role of the delta-like homologue 1 (Dlk1) in the regulation of the fibrotic response. Here, we investigated whether Dlk1 is involved in cardiac fibroblast-to-myofibroblast differentiation and regulates myocardial fibrosis and explored the molecular mechanism underpinning its effects in this process.

Deletion of Dlk2 increases the vulnerability to anxiety-like behaviors and impairs the anxiolytic action of alprazolam.

The purpose of this study was to evaluate the role of the non-canonical DLK2 NOTCH ligand in the regulation of emotional behavior. To this aim, anxiety and depressive-like behaviors were examined in Dlk2 knock-out (Dlk2) and its corresponding wild-type (WT) mice. Furthermore, relative gene expression analyses of corticotropin releasing hormone (Crh) in the paraventricular nucleus (PVN), glucocorticoid receptor (NR3C1) and FK506 binding protein 5 (FKBP5) in the hippocampus (HIPP), and the transcription factors Hes1, Hes5 and Hey1 in the PVN, HIPP and amygdala (AMY) were carried out in Dlk2 and WT mice under basal conditions and after exposure to restraint stress.

Absence of Notch1 in murine myeloid cells attenuates the development of experimental autoimmune encephalomyelitis by affecting Th1 and Th17 priming.

Inhibition of Notch signalling in T cells attenuates the development of experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. Growing evidence indicates that myeloid cells are also key players in autoimmune processes. Thus, the present study evaluates the role of the Notch1 receptor in myeloid cells on the progression of myelin oligodendrocyte glycoprotein (MOG) -induced EAE, using mice with a myeloid-specific deletion of the Notch1 gene (MyeNotch1KO).

Different expression levels of DLK1 inversely modulate the oncogenic potential of human MDA-MB-231 breast cancer cells through inhibition of NOTCH1 signaling.

NOTCH receptors participate in cancer cell proliferation and survival. Accumulated evidence indicates that, depending on the cellular context, these receptors can function as oncogenes or as tumor-suppressor genes. The epidermal growth factor-like protein delta-like homolog (DLK)1 acts as a NOTCH inhibitor and is involved in the regulation of normal and tumoral growth.

The Tetraspanin TSPAN33 Controls TLR-Triggered Macrophage Activation through Modulation of NOTCH Signaling.

The involvement of NOTCH signaling in macrophage activation by Toll receptors has been clearly established, but the factors and pathways controlling NOTCH signaling during this process have not been completely delineated yet. We have characterized the role of TSPAN33, a tetraspanin implicated in a disintegrin and metalloproteinase (ADAM) 10 maturation, during macrophage proinflammatory activation. Tspan33 expression increases in response to TLR signaling, including responses triggered by TLR4, TLR3, and TLR2 activation, and it is enhanced by IFN-γ.

Evidence of non-canonical NOTCH signaling: Delta-like 1 homolog (DLK1) directly interacts with the NOTCH1 receptor in mammals.

Canonical NOTCH signaling, known to be essential for tissue development, requires the Delta-Serrate-LAG2 (DSL) domain for NOTCH to interact with its ligand. However, despite lacking DSL, Delta-like 1 homolog (DLK1), a protein that plays a significant role in mammalian development, has been suggested to interact with NOTCH1 and act as an antagonist. This non-canonical interaction is, however controversial, and evidence for a direct interaction, still lacking in mammals.

DLK1 is a novel inflammatory inhibitor which interferes with NOTCH1 signaling in TLR-activated murine macrophages.

Delta-like protein 1 (DLK1) is a noncanonical ligand that inhibits NOTCH1 receptor activity and regulates multiple differentiation processes. In macrophages, NOTCH signaling increases TLR-induced expression of key pro-inflammatory mediators. We have investigated the role of DLK1 in macrophage activation and inflammation using Dlk1-deficient mice and Raw 264.

DLK1 Regulates Whole-Body Glucose Metabolism: A Negative Feedback Regulation of the Osteocalcin-Insulin Loop.

The endocrine role of the skeleton in regulating energy metabolism is supported by a feed-forward loop between circulating osteoblast (OB)-derived undercarboxylated osteocalcin (Glu-OCN) and pancreatic β-cell insulin; in turn, insulin favors osteocalcin (OCN) bioactivity. These data suggest the existence of a negative regulation of this cross talk between OCN and insulin. Recently, we identified delta like-1 (DLK1) as an endocrine regulator of bone turnover.

The proteins DLK1 and DLK2 modulate NOTCH1-dependent proliferation and oncogenic potential of human SK-MEL-2 melanoma cells.

NOTCH receptors regulate cell proliferation and survival in several types of cancer cells. Depending on the cellular context, NOTCH1 can function as an oncogene or as a tumor suppressor gene. DLK1 is also involved in the regulation of cell growth and cancer, but nothing is known about the role of DLK2 in these processes.

DLK1 regulates branching morphogenesis and parasympathetic innervation of salivary glands through inhibition of NOTCH signalling.

Background Information: Delta-like proteins 1 and 2 (DLK1, 2) are NOTCH receptor ligands containing epidermal growth factor-like repeats, which regulate NOTCH signalling. We investigated the role of DLK and the NOTCH pathway in the morphogenesis of the submandibular salivary glands (SMGs), using in vitro organotypic cultures.

Results: DLK1 and 2 were present in all stages of SMG morphogenesis, where DLK1 inhibited both NOTCH activity and SMG branching.

Dlk1 promotes a fast motor neuron biophysical signature required for peak force execution.

Motor neurons, which relay neural commands to drive skeletal muscle movements, encompass types ranging from "slow" to "fast," whose biophysical properties govern the timing, gradation, and amplitude of muscle force. Here we identify the noncanonical Notch ligand Delta-like homolog 1 (Dlk1) as a determinant of motor neuron functional diversification. Dlk1, expressed by ~30% of motor neurons, is necessary and sufficient to promote a fast biophysical signature in the mouse and chick.

Dual role of delta-like 1 homolog (DLK1) in skeletal muscle development and adult muscle regeneration.

Muscle development and regeneration is tightly orchestrated by a specific set of myogenic transcription factors. However, factors that regulate these essential myogenic inducers remain poorly described. Here, we show that delta-like 1 homolog (Dlk1), an imprinted gene best known for its ability to inhibit adipogenesis, is a crucial regulator of the myogenic program in skeletal muscle.