The Experts below are selected from a list of 3765 Experts worldwide ranked by ideXlab platform

Moustapha Kassem - One of the best experts on this subject based on the ideXlab platform.

  • delta like 1 DLK1 is a possible mediator of vitamin d effects on bone and energy metabolism
    Bone, 2020
    Co-Authors: Aya Bassatne, Moustapha Kassem, Abbas Jafari, Christos S Mantzoros, Maya Rahme, Ghada Elhajj Fuleihan
    Abstract:

    Abstract Vitamin D effects on bone and mineral metabolism are well recognized, and its anti-inflammatory actions are gaining particular interest. Delta-like 1 (DLK1) is a protein, expressed by progenitor cells of different tissues, and increases the size of progenitor cell population during the inflammatory phase of tissue regeneration. DLK1 also plays a role in energy metabolism as it antagonizes insulin signaling in bone. In this one-year randomized clinical trial of overweight elderly individuals that received either 600 or 3750 IU daily cholecalciferol we assessed the effect of vitamin D supplementation on pre-specified secondary outcomes: DLK1, leptin, adiponectin, C-Reactive Protein (CRP) and Vascular Cell Adhesion Molecule (VCAM). We also examined correlations between DLK1and bone (BMD, bone markers), fat (adipokines, body composition), insulin sensitivity and inflammatory markers. Multivariate analyses were conducted to further explore these associations. Overall, there was a significant increase in serum DLK1 and leptin and a decrease in VCAM, but no change in CRP, after 12 months of vitamin D supplementation. DLK1 was negatively correlated with BMD and positively correlated with bone markers, associations that persisted after adjusting for age, gender and BMI. DLK1 was also positively associated with indices of insulin resistance and negatively with indices of insulin sensitivity. Correlations between DLK1 and fat parameters, such as adipokines, and DXA derived fat mass were less consistent. There were no correlations between DLK1 and inflammatory markers. In conclusion, twelve months supplementation of vitamin D3 increased serum DLK1. DLK1 was negatively associated with indices of bone health and fuel metabolism, and with 1,25(OH)2D levels. Similar to the role of DLK1 in animal models, our findings support the hypothesis that DLK1 can be targeted to regulate bone and energy metabolism and develop drugs to improve BMD and insulin sensitivity. However, further studies are needed to explore the role of DLK1 and its relationship to vitamin D metabolites in vivo.

  • Antibody-based inhibition of circulating DLK1 protects from estrogen deficiency-induced bone loss in mice
    Bone, 2018
    Co-Authors: Florence Figeac, Ditte C. Andersen, Casper A. Nipper Nielsen, Nicholas Ditzel, Søren P. Sheikh, Charlotte H. Jensen, Karsten Skjødt, Moustapha Kassem, Basem M. Abdallah
    Abstract:

    Soluble delta-like 1 homolog (DLK1) is a circulating protein that belongs to the Notch/Serrate/delta family, which regulates many differentiation processes including osteogenesis and adipogenesis. We have previously demonstrated an inhibitory effect of DLK1 on bone mass via stimulation of bone resorption and inhibition of bone formation. Further, serum DLK1 levels are elevated and positively correlated to bone turnover markers in estrogen (E)-deficient rodents and women. In this report, we examined whether inhibition of serum DLK1 activity using a neutralizing monoclonal antibody protects from E deficiency-associated bone loss in mice. Thus, we generated mouse monoclonal anti-mouse DLK1 antibodies (MAb DLK1) that enabled us to reduce and also quantitate the levels of bioavailable serum DLK1 in vivo. Ovariectomized (ovx) mice were injected intraperitoneally twice weekly with MAb DLK1 over a period of one month. DEXA-, microCT scanning, and bone histomorphometric analyses were performed. Compared to controls, MAb DLK1 treated ovx mice were protected against ovx-induced bone loss, as revealed by significantly increased total bone mass (BMD) due to increased trabecular bone volume fraction (BV/TV) and inhibition of bone resorption. No significant changes were observed in total fat mass or in the number of bone marrow adipocytes. These results support the potential use of anti-DLK1 antibody therapy as a novel intervention to protect from E deficiency associated bone loss.

  • DLK1 regulates whole body glucose metabolism a negative feedback regulation of the osteocalcin insulin loop
    Diabetes, 2015
    Co-Authors: Basem M. Abdallah, Nicholas Ditzel, Moustapha Kassem, Jorge Laborda, Gerard Karsenty
    Abstract:

    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. Because DLK1 is colocalized with insulin in pancreatic β-cells, we examined the role of DLK1 in insulin signaling in OBs and energy metabolism. We show that Glu-OCN specifically stimulates DLK1 expression by the pancreas. Conversely, DLK1 -deficient ( DLK1 −/− ) mice exhibited increased circulating Glu-OCN levels and increased insulin sensitivity, whereas mice overexpressing DLK1 in OB displayed reduced insulin secretion and sensitivity due to impaired insulin signaling in OB and lowered Glu-OCN serum levels. Furthermore, DLK1 −/− mice treated with Glu-OC experienced significantly lower blood glucose levels than Glu-OCN–treated wild-type mice. The data suggest that Glu-OCN–controlled production of DLK1 by pancreatic β-cells acts as a negative feedback mechanism to counteract the stimulatory effects of insulin on OB production of Glu-OCN, a potential mechanism preventing OCN-induced hypoglycemia.

  • dual role of delta like 1 homolog DLK1 in skeletal muscle development and adult muscle regeneration
    Development, 2013
    Co-Authors: Søren P. Sheikh, Moustapha Kassem, Jorge Laborda, Ditte Caroline Andersen, Victoriano Baladron, Charlotte Harken Jensen
    Abstract:

    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. DLK1 -/- mice were developmentally retarded in their muscle mass and function owing to inhibition of the myogenic program during embryogenesis. Surprisingly however, DLK1 depletion improves in vitro and in vivo adult skeletal muscle regeneration by substantial enhancement of the myogenic program and muscle function, possibly by means of an increased number of available myogenic precursor cells. By contrast, DLK1 fails to alter the adipogenic commitment of muscle-derived progenitors in vitro , as well as intramuscular fat deposition during in vivo regeneration. Collectively, our results suggest a novel and surprising dual biological function of DLK1 as an enhancer of muscle development, but as an inhibitor of adult muscle regeneration.

  • delta like 1 fetal antigen 1 DLK1 fa1 is a novel regulator of chondrogenic cell differentiation via inhibition of the akt kinase dependent pathway
    Journal of Biological Chemistry, 2011
    Co-Authors: Li Chen, Basem M. Abdallah, Charlotte Harken Jensen, Jorge Laborda, Diyako Werya Mohamed Qanie, Abbas Jafari, Hanna Taipaleenmaki, Annamarja Saamanen, Maria Luisa Nueda Sanz, Moustapha Kassem
    Abstract:

    Delta-like 1 (DLK1, also known as fetal antigen-1, FA1) is a member of Notch/Delta family that inhibits adipocyte and osteoblast differentiation; however, its role in chondrogenesis is still not clear. Thus, we overexpressed DLK1/FA1 in mouse embryonic ATDC5 cells and tested its effects on chondrogenic differentiation. DLK1/FA1 inhibited insulin-induced chondrogenic differentiation as evidenced by reduction of cartilage nodule formation and gene expression of aggrecan, collagen Type II and X. Similar effects were obtained either by using DLK1/FA1-conditioned medium or by addition of a purified, secreted, form of DLK1 (FA1) directly to the induction medium. The inhibitory effects of DLK1/FA1 were dose-dependent and occurred irrespective of the chondrogenic differentiation stage: proliferation, differentiation, maturation, or hypertrophic conversion. Overexpression or addition of the DLK1/FA1 protein to the medium strongly inhibited the activation of Akt, but not the ERK1/2, or p38 MAPK pathways, and the inhibition of Akt by DLK1/FA1 was mediated through PI3K activation. Interestingly, inhibition of fibronectin expression by siRNA rescued the DLK1/FA1-mediated inhibition of Akt, suggesting interaction of DLK1/FA1 and fibronectin in chondrogenic cells. Our results identify DLK1/FA1 as a novel regulator of chondrogenesis and suggest DLK1/FA1 acts as an inhibitor of the PI3K/Akt pathways that leads to its inhibitory effects on chondrogenesis.

Charlotte Harken Jensen - One of the best experts on this subject based on the ideXlab platform.

  • 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
    EBioMedicine, 2019
    Co-Authors: Charlotte Harken Jensen, Rok Kosmina, Mikael Ryden, Christina Baun, Svend Hvidsten, Marianne Andersen, Louise Lehmann Christensen, Amalia Gastaldelli, Paolo Marraccini
    Abstract:

    Abstract 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. Confirmatory animal studies performed in normal (NC) and high fat diet (HFD) fed DLK1+/+ and DLK1−/− mice included DXA scanning, glucose tolerance tests (GTTs), blood measurements, and skeletal muscle glucose uptake studies by positron emission tomography (PET), histology, qRT-PCR, and in vitro cell studies. Findings Overall, DLK1 is positively correlated with fat amounts, which is consistent with a negative linear relationship between DLK1 and GDR. This relationship is not mediated by age, BMI, or fat percentage. In support, DLK1 also correlates positively with HOMA-IR and ADIPO-IR in these humans, but has no linear relationship with the early diabetic inflammation marker MCP-1. In DLK1−/− mice, the increase in fat percentage and adipocyte size induced by HFD is attenuated, and these animals are protected against insulin resistance. These DLK1 effects seem independent of gluconeogenesis, but at least partly relies on increased in vivo glucose uptake in skeletal muscles by DLK1 regulating the major glucose transporter Glut4 in vivo as well as in two independent cell lines. Interpretation Thus, instead of an adipogenic inhibitor, DLK1 should be regarded as a factor causally linked to obesity and insulin resistance, and may be used to predict development of type 2 diabetes. Fund The Danish Diabetes Academy supported by the Novo Nordisk Foundation , The Danish National Research Council (# 09-073648 ), The Lundbeck Foundation , University of Southern Denmark , and Dep. Of Clinical Biochemistry and Pharmacology/Odense University Hospital , the Swedish Research Council , the Swedish Diabetes Foundation , the Strategic Research Program in Diabetes at Karolinska Institute and an EFSD/Lilly grant.

  • Expression and Functional Analyses of DLK1 in Muscle Stem Cells and Mesenchymal Progenitors during Muscle Regeneration
    International Journal of Molecular Sciences, 2019
    Co-Authors: Lidan Zhang, Charlotte Harken Jensen, Ditte Caroline Andersen, Akiyoshi Uezumi, Takayuki Kaji, Kazutake Tsujikawa, So-ichiro Fukada
    Abstract:

    Delta like non-canonical Notch ligand 1 (DLK1) is a paternally expressed gene which is also known as preadipocyte factor 1 (Pref−1). The accumulation of adipocytes and expression of DLK1 in regenerating muscle suggests a correlation between fat accumulation and DLK1 expression in the muscle. Additionally, mice overexpressing DLK1 show increased muscle weight, while DLK1-null mice exhibit decreased body weight and muscle mass, indicating that DLK1 is a critical factor in regulating skeletal muscle mass during development. The muscle regeneration process shares some features with muscle development. However, the role of DLK1 in regeneration processes remains controversial. Here, we show that mesenchymal progenitors also known as adipocyte progenitors exclusively express DLK1 during muscle regeneration. Eliminating developmental effects, we used conditional depletion models to examine the specific roles of DLK1 in muscle stem cells or mesenchymal progenitors. Unexpectedly, deletion of DLK1 in neither the muscle stem cells nor the mesenchymal progenitors affected the regenerative ability of skeletal muscle. In addition, fat accumulation was not increased by the loss of DLK1. Collectively, DLK1 plays essential roles in muscle development, but does not greatly impact regeneration processes and adipogenic differentiation in adult skeletal muscle regeneration.

  • The non-canonical NOTCH1 ligand Delta-like 1 homolog (DLK1) self interacts in mammals
    International Journal of Biological Macromolecules, 2017
    Co-Authors: Gunnhildur Asta Traustadottir, Søren P. Sheikh, Charlotte Harken Jensen, Jose Javier Garcia Ramirez, Hans Christian Beck, Ditte Caroline Andersen
    Abstract:

    Abstract Delta-like 1 homolog (DLK1) is an imprinted gene, which is widely expressed during mammalian development and plays a pivotal role in differentiation of various tissue types. Most recently, we have shown that DLK1 interacts with NOTCH1, yet several Notch independent mechanisms have previously been suggested as well, but only poorly confirmed in a mammalian context. In the present study, we employed the mammalian two-hybrid (MTH) system, a genetic in vivo protein–protein interaction system, to show robust DLK1-DLK1, DLK1-FnI (Fibronectin) and DLK1-CFR (cysteine-rich FGF receptor) interactions, whereas the proposed DLK1-IGFBP1 interaction was not supported by MTH. Very little has previously been described on the DLK1 self-interaction. Herein, we showed by immunoprecipitation as well as Sulfo-SBED label transfer that the DLK1-DLK1 interaction likely is part of DLK1’s function in preadipocytes. Furthermore our data suggest that DLK1 interacts with itself through EGF domain 4 and 5, which is distinct from the recently described NOTCH1-DLK1 interaction, which occurs between EGF domain 5 and 6. This opens up the possibility that Notch independent mechanisms like the DLK1-DLK1 interaction may modulate the non-canonical NOTCH1-DLK1 interaction further complexing this system.

  • evidence of non canonical notch signaling delta like 1 homolog DLK1 directly interacts with the notch1 receptor in mammals
    Cellular Signalling, 2016
    Co-Authors: Gunnhildur Asta Traustadottir, Søren P. Sheikh, Charlotte Harken Jensen, Sussi B Mortensen, Mads Thomassen, Jorge Laborda, Victoriano Baladron, Hans Christian Beck, Ditte Caroline Andersen
    Abstract:

    Abstract 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. In this study, we elucidated the putative DLK1-NOTCH1 interaction in a mammalian context. Taking a global approach and using DLK1+/+ and DLK1−/− mouse tissues at E16.5, we demonstrated that several NOTCH signaling pathways indeed are affected by DLK1 during tissue development, and this was supported by a lower activation of NOTCH1 protein in DLK1+/+ embryos. Likewise, but using a distinct DLK1-manipulated (siRNA) setup in a mammalian cell line, NOTCH signaling was substantially inhibited by DLK1. Using a mammalian two-hybrid system, we firmly established that the effect of DLK1 on NOTCH signaling was due to a direct interaction between DLK1 and NOTCH1. By careful dissection of this mechanism, we found this interaction to occur between EGF domains 5 and 6 of DLK1 and EGF domains 10–15 of NOTCH1. Thus, our data provide the first evidence for a direct interaction between DLK1 and NOTCH1 in mammals, and substantiate that non-canonical NOTCH ligands exist, adding to the complexity of NOTCH signaling.

  • dual role of delta like 1 homolog DLK1 in skeletal muscle development and adult muscle regeneration
    Development, 2013
    Co-Authors: Søren P. Sheikh, Moustapha Kassem, Jorge Laborda, Ditte Caroline Andersen, Victoriano Baladron, Charlotte Harken Jensen
    Abstract:

    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. DLK1 -/- mice were developmentally retarded in their muscle mass and function owing to inhibition of the myogenic program during embryogenesis. Surprisingly however, DLK1 depletion improves in vitro and in vivo adult skeletal muscle regeneration by substantial enhancement of the myogenic program and muscle function, possibly by means of an increased number of available myogenic precursor cells. By contrast, DLK1 fails to alter the adipogenic commitment of muscle-derived progenitors in vitro , as well as intramuscular fat deposition during in vivo regeneration. Collectively, our results suggest a novel and surprising dual biological function of DLK1 as an enhancer of muscle development, but as an inhibitor of adult muscle regeneration.

Jorge Laborda - One of the best experts on this subject based on the ideXlab platform.

  • Deletion of DLK1 increases the vulnerability to developing anxiety-like behaviors and ethanol consumption in mice
    Biochemical Pharmacology, 2018
    Co-Authors: María Salud García-gutiérrez, Jorge Laborda, Francisco Navarrete, Jorge Manzanares
    Abstract:

    Abstract 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. Quantitative real time polymerase chain reaction (qPCR) studies were carried out to evaluate alterations in targets closely related to DA neurotransmission in the reward system, tyrosine hydroxylase (Th) in the ventral tegmental area (VTA), and μ-opioid receptor (Oprm1) in the nucleus accumbens (NAc). No differences were observed in the total or peripheral distances travelled by DLK1−/− compared to wild-type (WT) mice in OF. However, central distance travelled significantly decreased in DLK1−/− mice. Deletion of DLK1 increased anxiety-like behaviors in the LDB and EPM, and, DLK1−/− mice also presented higher ethanol intake and motivation to drink (number of effective responses) in the OEA. In addition, Th and Oprm1 gene expression was reduced in the VTA and NAc of DLK1−/− mice. We conclude that deletion of DLK1 increases anxiety-related behaviors and vulnerability to ethanol consumption and modifies the gene expression of key targets closely related with DA neurotransmission involved in the reinforcing actions of ethanol.

  • evidence of non canonical notch signaling delta like 1 homolog DLK1 directly interacts with the notch1 receptor in mammals
    Cellular Signalling, 2016
    Co-Authors: Gunnhildur Asta Traustadottir, Søren P. Sheikh, Charlotte Harken Jensen, Sussi B Mortensen, Mads Thomassen, Jorge Laborda, Victoriano Baladron, Hans Christian Beck, Ditte Caroline Andersen
    Abstract:

    Abstract 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. In this study, we elucidated the putative DLK1-NOTCH1 interaction in a mammalian context. Taking a global approach and using DLK1+/+ and DLK1−/− mouse tissues at E16.5, we demonstrated that several NOTCH signaling pathways indeed are affected by DLK1 during tissue development, and this was supported by a lower activation of NOTCH1 protein in DLK1+/+ embryos. Likewise, but using a distinct DLK1-manipulated (siRNA) setup in a mammalian cell line, NOTCH signaling was substantially inhibited by DLK1. Using a mammalian two-hybrid system, we firmly established that the effect of DLK1 on NOTCH signaling was due to a direct interaction between DLK1 and NOTCH1. By careful dissection of this mechanism, we found this interaction to occur between EGF domains 5 and 6 of DLK1 and EGF domains 10–15 of NOTCH1. Thus, our data provide the first evidence for a direct interaction between DLK1 and NOTCH1 in mammals, and substantiate that non-canonical NOTCH ligands exist, adding to the complexity of NOTCH signaling.

  • DLK1 regulates whole body glucose metabolism a negative feedback regulation of the osteocalcin insulin loop
    Diabetes, 2015
    Co-Authors: Basem M. Abdallah, Nicholas Ditzel, Moustapha Kassem, Jorge Laborda, Gerard Karsenty
    Abstract:

    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. Because DLK1 is colocalized with insulin in pancreatic β-cells, we examined the role of DLK1 in insulin signaling in OBs and energy metabolism. We show that Glu-OCN specifically stimulates DLK1 expression by the pancreas. Conversely, DLK1 -deficient ( DLK1 −/− ) mice exhibited increased circulating Glu-OCN levels and increased insulin sensitivity, whereas mice overexpressing DLK1 in OB displayed reduced insulin secretion and sensitivity due to impaired insulin signaling in OB and lowered Glu-OCN serum levels. Furthermore, DLK1 −/− mice treated with Glu-OC experienced significantly lower blood glucose levels than Glu-OCN–treated wild-type mice. The data suggest that Glu-OCN–controlled production of DLK1 by pancreatic β-cells acts as a negative feedback mechanism to counteract the stimulatory effects of insulin on OB production of Glu-OCN, a potential mechanism preventing OCN-induced hypoglycemia.

  • DLK1 is a novel inflammatory inhibitor which interferes with NOTCH1 signaling in TLR-activated murine macrophages.
    European Journal of Immunology, 2015
    Co-Authors: María Jesús González González, Jorge Laborda, Eva M Monsalve, Almudena Ruiz-garcía, Ricardo Sánchez-prieto, María José Díaz-guerra, María J. Ruiz-hidalgo
    Abstract:

    : 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 264.7 cells overexpressing DLK1. In the absence of DLK1, NOTCH1 expression is increased and the activation of macrophages with TLR3 or TLR4 agonists leads to higher production of IFN-β and other pro-inflammatory cytokines, including TNF-α, IL-12, and IL-23. The expression of key proteins involved in IFN-β signaling, such as IRF3, IRF7, IRF1, or STAT1, as well as cRel, or RelB, which are responsible for the generation of IL-12 and IL-23, is enhanced in DLK1 KO macrophages. Consistently, DLK1 KO mice are more sensitive to LPS-induced endotoxic shock. These effects seem to be mediated through the modulation of NOTCH1 signaling. TLR4 activation reduces DLK1 expression, whereas increases NOTCH1 levels. In addition, DLK1 expression diminishes during differentiation of human U937 cells to macrophages. Overall, these results reveal a novel role for DLK1 as a regulator of NOTCH-mediated, pro-inflammatory macrophage activation, which could help to ensure a baseline level preventing constant tissue inflammation.

  • the proteins DLK1 and dlk2 modulate notch1 dependent proliferation and oncogenic potential of human sk mel 2 melanoma cells
    Biochimica et Biophysica Acta, 2014
    Co-Authors: Maria Luisa Nueda, Victoriano Baladron, Anaisabel Naranjo, Jorge Laborda
    Abstract:

    Abstract 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. Recently, the proteins DLK1 and DLK2 have been reported to interact with NOTCH1 and to inhibit NOTCH1 activation and signaling in different cell lines. In this work, we focused on the role of DLK proteins in the control of melanoma cell growth, where NOTCH1 is known to exert an oncogenic effect. We found that human DLK proteins inhibit NOTCH signaling in SK-MEL-2 metastatic melanoma cells. Moreover, the proliferation rate of these cells was dependent upon the level of NOTCH activation and signaling as regulated by DLK proteins. In particular, high levels of NOTCH inhibition resulted in a decrease, whereas lower levels of NOTCH inhibition led to an increase in melanoma cell proliferation rates, both in vitro and in vivo . Finally, our data revealed additive NOTCH-mediated effects of DLK proteins and the γ-secretase inhibitor DAPT on cell proliferation. The data presented in this work suggest that a fine regulation of NOTCH signaling plays an important role in the control of metastatic melanoma cell proliferation. Our results open the way to new research on the role of DLK proteins as potential therapeutic tools for the treatment of human melanoma.

Ditte Caroline Andersen - One of the best experts on this subject based on the ideXlab platform.

  • Expression and Functional Analyses of DLK1 in Muscle Stem Cells and Mesenchymal Progenitors during Muscle Regeneration
    International Journal of Molecular Sciences, 2019
    Co-Authors: Lidan Zhang, Charlotte Harken Jensen, Ditte Caroline Andersen, Akiyoshi Uezumi, Takayuki Kaji, Kazutake Tsujikawa, So-ichiro Fukada
    Abstract:

    Delta like non-canonical Notch ligand 1 (DLK1) is a paternally expressed gene which is also known as preadipocyte factor 1 (Pref−1). The accumulation of adipocytes and expression of DLK1 in regenerating muscle suggests a correlation between fat accumulation and DLK1 expression in the muscle. Additionally, mice overexpressing DLK1 show increased muscle weight, while DLK1-null mice exhibit decreased body weight and muscle mass, indicating that DLK1 is a critical factor in regulating skeletal muscle mass during development. The muscle regeneration process shares some features with muscle development. However, the role of DLK1 in regeneration processes remains controversial. Here, we show that mesenchymal progenitors also known as adipocyte progenitors exclusively express DLK1 during muscle regeneration. Eliminating developmental effects, we used conditional depletion models to examine the specific roles of DLK1 in muscle stem cells or mesenchymal progenitors. Unexpectedly, deletion of DLK1 in neither the muscle stem cells nor the mesenchymal progenitors affected the regenerative ability of skeletal muscle. In addition, fat accumulation was not increased by the loss of DLK1. Collectively, DLK1 plays essential roles in muscle development, but does not greatly impact regeneration processes and adipogenic differentiation in adult skeletal muscle regeneration.

  • The non-canonical NOTCH1 ligand Delta-like 1 homolog (DLK1) self interacts in mammals
    International Journal of Biological Macromolecules, 2017
    Co-Authors: Gunnhildur Asta Traustadottir, Søren P. Sheikh, Charlotte Harken Jensen, Jose Javier Garcia Ramirez, Hans Christian Beck, Ditte Caroline Andersen
    Abstract:

    Abstract Delta-like 1 homolog (DLK1) is an imprinted gene, which is widely expressed during mammalian development and plays a pivotal role in differentiation of various tissue types. Most recently, we have shown that DLK1 interacts with NOTCH1, yet several Notch independent mechanisms have previously been suggested as well, but only poorly confirmed in a mammalian context. In the present study, we employed the mammalian two-hybrid (MTH) system, a genetic in vivo protein–protein interaction system, to show robust DLK1-DLK1, DLK1-FnI (Fibronectin) and DLK1-CFR (cysteine-rich FGF receptor) interactions, whereas the proposed DLK1-IGFBP1 interaction was not supported by MTH. Very little has previously been described on the DLK1 self-interaction. Herein, we showed by immunoprecipitation as well as Sulfo-SBED label transfer that the DLK1-DLK1 interaction likely is part of DLK1’s function in preadipocytes. Furthermore our data suggest that DLK1 interacts with itself through EGF domain 4 and 5, which is distinct from the recently described NOTCH1-DLK1 interaction, which occurs between EGF domain 5 and 6. This opens up the possibility that Notch independent mechanisms like the DLK1-DLK1 interaction may modulate the non-canonical NOTCH1-DLK1 interaction further complexing this system.

  • evidence of non canonical notch signaling delta like 1 homolog DLK1 directly interacts with the notch1 receptor in mammals
    Cellular Signalling, 2016
    Co-Authors: Gunnhildur Asta Traustadottir, Søren P. Sheikh, Charlotte Harken Jensen, Sussi B Mortensen, Mads Thomassen, Jorge Laborda, Victoriano Baladron, Hans Christian Beck, Ditte Caroline Andersen
    Abstract:

    Abstract 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. In this study, we elucidated the putative DLK1-NOTCH1 interaction in a mammalian context. Taking a global approach and using DLK1+/+ and DLK1−/− mouse tissues at E16.5, we demonstrated that several NOTCH signaling pathways indeed are affected by DLK1 during tissue development, and this was supported by a lower activation of NOTCH1 protein in DLK1+/+ embryos. Likewise, but using a distinct DLK1-manipulated (siRNA) setup in a mammalian cell line, NOTCH signaling was substantially inhibited by DLK1. Using a mammalian two-hybrid system, we firmly established that the effect of DLK1 on NOTCH signaling was due to a direct interaction between DLK1 and NOTCH1. By careful dissection of this mechanism, we found this interaction to occur between EGF domains 5 and 6 of DLK1 and EGF domains 10–15 of NOTCH1. Thus, our data provide the first evidence for a direct interaction between DLK1 and NOTCH1 in mammals, and substantiate that non-canonical NOTCH ligands exist, adding to the complexity of NOTCH signaling.

  • dual role of delta like 1 homolog DLK1 in skeletal muscle development and adult muscle regeneration
    Development, 2013
    Co-Authors: Søren P. Sheikh, Moustapha Kassem, Jorge Laborda, Ditte Caroline Andersen, Victoriano Baladron, Charlotte Harken Jensen
    Abstract:

    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. DLK1 -/- mice were developmentally retarded in their muscle mass and function owing to inhibition of the myogenic program during embryogenesis. Surprisingly however, DLK1 depletion improves in vitro and in vivo adult skeletal muscle regeneration by substantial enhancement of the myogenic program and muscle function, possibly by means of an increased number of available myogenic precursor cells. By contrast, DLK1 fails to alter the adipogenic commitment of muscle-derived progenitors in vitro , as well as intramuscular fat deposition during in vivo regeneration. Collectively, our results suggest a novel and surprising dual biological function of DLK1 as an enhancer of muscle development, but as an inhibitor of adult muscle regeneration.

  • membrane tethered delta like 1 homolog DLK1 restricts adipose tissue size by inhibiting preadipocyte proliferation
    Diabetes, 2012
    Co-Authors: Sussi B Mortensen, Søren P. Sheikh, Charlotte Harken Jensen, Mikael Schneider, Mads Thomassen, Torben A Kruse, Jorge Laborda, Ditte Caroline Andersen
    Abstract:

    Adipocyte renewal from preadipocytes has been shown to occur throughout life and to contribute to obesity, yet very little is known about the molecular circuits that control preadipocyte expansion. The soluble form of the preadipocyte factor (also known as pref-1) delta-like 1 homolog (DLK1S) is known to inhibit adipogenic differentiation; however, the impact of DLK1 isoforms on preadipocyte proliferation remains to be determined. We generated preadipocytes with different levels of DLK1 and examined differentially affected gene pathways, which were functionally tested in vitro and confirmed in vivo. Here, we demonstrate for the first time that only membrane-bound DLK1 (DLK1M) exhibits a substantial repression effect on preadipocyte proliferation. Thus, by independently manipulating DLK1 isoform levels, we established that DLK1M inhibits G1-to-S-phase cell cycle progression and thereby strongly inhibits preadipocyte proliferation in vitro. Adult DLK1-null mice exhibit higher fat amounts than wild-type controls, and our in vivo analysis demonstrates that this may be explained by a marked increase in preadipocyte replication. Together, these data imply a major dual inhibitory function of DLK1 on adipogenesis, which places DLK1 as a master regulator of preadipocyte homeostasis, suggesting that DLK1 manipulation may open new avenues in obesity treatment.

Basem M. Abdallah - One of the best experts on this subject based on the ideXlab platform.

  • Antibody-based inhibition of circulating DLK1 protects from estrogen deficiency-induced bone loss in mice
    Bone, 2018
    Co-Authors: Florence Figeac, Ditte C. Andersen, Casper A. Nipper Nielsen, Nicholas Ditzel, Søren P. Sheikh, Charlotte H. Jensen, Karsten Skjødt, Moustapha Kassem, Basem M. Abdallah
    Abstract:

    Soluble delta-like 1 homolog (DLK1) is a circulating protein that belongs to the Notch/Serrate/delta family, which regulates many differentiation processes including osteogenesis and adipogenesis. We have previously demonstrated an inhibitory effect of DLK1 on bone mass via stimulation of bone resorption and inhibition of bone formation. Further, serum DLK1 levels are elevated and positively correlated to bone turnover markers in estrogen (E)-deficient rodents and women. In this report, we examined whether inhibition of serum DLK1 activity using a neutralizing monoclonal antibody protects from E deficiency-associated bone loss in mice. Thus, we generated mouse monoclonal anti-mouse DLK1 antibodies (MAb DLK1) that enabled us to reduce and also quantitate the levels of bioavailable serum DLK1 in vivo. Ovariectomized (ovx) mice were injected intraperitoneally twice weekly with MAb DLK1 over a period of one month. DEXA-, microCT scanning, and bone histomorphometric analyses were performed. Compared to controls, MAb DLK1 treated ovx mice were protected against ovx-induced bone loss, as revealed by significantly increased total bone mass (BMD) due to increased trabecular bone volume fraction (BV/TV) and inhibition of bone resorption. No significant changes were observed in total fat mass or in the number of bone marrow adipocytes. These results support the potential use of anti-DLK1 antibody therapy as a novel intervention to protect from E deficiency associated bone loss.

  • DLK1 regulates whole body glucose metabolism a negative feedback regulation of the osteocalcin insulin loop
    Diabetes, 2015
    Co-Authors: Basem M. Abdallah, Nicholas Ditzel, Moustapha Kassem, Jorge Laborda, Gerard Karsenty
    Abstract:

    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. Because DLK1 is colocalized with insulin in pancreatic β-cells, we examined the role of DLK1 in insulin signaling in OBs and energy metabolism. We show that Glu-OCN specifically stimulates DLK1 expression by the pancreas. Conversely, DLK1 -deficient ( DLK1 −/− ) mice exhibited increased circulating Glu-OCN levels and increased insulin sensitivity, whereas mice overexpressing DLK1 in OB displayed reduced insulin secretion and sensitivity due to impaired insulin signaling in OB and lowered Glu-OCN serum levels. Furthermore, DLK1 −/− mice treated with Glu-OC experienced significantly lower blood glucose levels than Glu-OCN–treated wild-type mice. The data suggest that Glu-OCN–controlled production of DLK1 by pancreatic β-cells acts as a negative feedback mechanism to counteract the stimulatory effects of insulin on OB production of Glu-OCN, a potential mechanism preventing OCN-induced hypoglycemia.

  • delta like 1 fetal antigen 1 DLK1 fa1 is a novel regulator of chondrogenic cell differentiation via inhibition of the akt kinase dependent pathway
    Journal of Biological Chemistry, 2011
    Co-Authors: Li Chen, Basem M. Abdallah, Charlotte Harken Jensen, Jorge Laborda, Diyako Werya Mohamed Qanie, Abbas Jafari, Hanna Taipaleenmaki, Annamarja Saamanen, Maria Luisa Nueda Sanz, Moustapha Kassem
    Abstract:

    Delta-like 1 (DLK1, also known as fetal antigen-1, FA1) is a member of Notch/Delta family that inhibits adipocyte and osteoblast differentiation; however, its role in chondrogenesis is still not clear. Thus, we overexpressed DLK1/FA1 in mouse embryonic ATDC5 cells and tested its effects on chondrogenic differentiation. DLK1/FA1 inhibited insulin-induced chondrogenic differentiation as evidenced by reduction of cartilage nodule formation and gene expression of aggrecan, collagen Type II and X. Similar effects were obtained either by using DLK1/FA1-conditioned medium or by addition of a purified, secreted, form of DLK1 (FA1) directly to the induction medium. The inhibitory effects of DLK1/FA1 were dose-dependent and occurred irrespective of the chondrogenic differentiation stage: proliferation, differentiation, maturation, or hypertrophic conversion. Overexpression or addition of the DLK1/FA1 protein to the medium strongly inhibited the activation of Akt, but not the ERK1/2, or p38 MAPK pathways, and the inhibition of Akt by DLK1/FA1 was mediated through PI3K activation. Interestingly, inhibition of fibronectin expression by siRNA rescued the DLK1/FA1-mediated inhibition of Akt, suggesting interaction of DLK1/FA1 and fibronectin in chondrogenic cells. Our results identify DLK1/FA1 as a novel regulator of chondrogenesis and suggest DLK1/FA1 acts as an inhibitor of the PI3K/Akt pathways that leads to its inhibitory effects on chondrogenesis.

  • DLK1 is a novel regulator of bone mass that mediates estrogen deficiency induced bone loss in mice
    Journal of Bone and Mineral Research, 2011
    Co-Authors: Nicholas Ditzel, Basem M. Abdallah, Jorge Laborda, Maria Jose Ruizhidalgo, Gunnhildur Asta Traustadottir, Amer Mahmood, Arndt F Schilling, Michael Amling, Moustapha Kassem
    Abstract:

    Delta-like 1/fetal antigen 1 (DLK1/FA-1) is a transmembrane protein belonging to the Notch/Delta family that acts as a membrane-associated or a soluble protein to regulate regeneration of a number of adult tissues. Here we examined the role of DLK1/FA-1 in bone biology using osteoblast-specific DLK1-overexpressing mice (Col1-DLK1). Col1-DLK1 mice displayed growth retardation and significantly reduced total body weight and bone mineral density (BMD). Micro–computed tomographis (µCT) scanning revealed a reduced trabecular and cortical bone volume fraction. Tissue-level histomorphometric analysis demonstrated decreased bone-formation rate and enhanced bone resorption in Col1-DLK1 mice compared with wild-type mice. At a cellular level, DLK1 markedly reduced the total number of bone marrow (BM)–derived colony-forming units fibroblasts (CFU-Fs), as well as their osteogenic capacity. In a number of in vitro culture systems, DLK1 stimulated osteoclastogenesis indirectly through osteoblast-dependent increased production of proinflammatory bone-resorbing cytokines (eg, Il7, Tnfa, and Ccl3). We found that ovariectomy (ovx)–induced bone loss was associated with increased production of DLK1 in the bone marrow by activated T cells. Interestingly, DLK1−/− mice were significantly protected from ovx-induced bone loss compared with wild-type mice. Thus we identified DLK1 as a novel regulator of bone mass that functions to inhibit bone formation and to stimulate bone resorption. Increasing DLK1 production by T cells under estrogen deficiency suggests its possible use as a therapeutic target for preventing postmenopausal bone loss. © 2011 American Society for Bone and Mineral Research.

  • DLK1 fa1 regulates the function of human bone marrow mesenchymal stem cells by modulating gene expression of pro inflammatory cytokines and immune response related factors
    Journal of Biological Chemistry, 2007
    Co-Authors: Basem M. Abdallah, Jorge Laborda, Gunnhildur Asta Traustadottir, Patrice Boissy, Jesper Dahlgaard, Katarzyna Kupisiewicz, Jeanmarie Delaisse, Moustapha Kassem
    Abstract:

    Abstract DLK1/FA1 (delta-like 1/fetal antigen-1) is a member of the epidermal growth factor-like homeotic protein family whose expression is known to modulate the differentiation signals of mesenchymal and hematopoietic stem cells in bone marrow. We have demonstrated previously that DLK1 can maintain the human bone marrow mesenchymal stem cells (hMSC) in an undifferentiated state. To identify the molecular mechanisms underlying these effects, we compared the basal gene expression pattern in DLK1-overexpressing hMSC cells (hMSC-DLK1) versus control hMSC (negative for DLK1 expression) by using Affymetrix HG-U133A microarrays. In response to DLK1 expression, 128 genes were significantly up-regulated (with >2-fold; p < 0.001), and 24% of these genes were annotated as immune response-related factors, including pro-inflammatory cytokines, in addition to factors involved in the complement system, apoptosis, and cell adhesion. Also, addition of purified FA1 to hMSC up-regulated the same factors in a dose-dependent manner. As biological consequences of up-regulating these immune response-related factors, we showed that the inhibitory effects of DLK1 on osteoblast and adipocyte differentiation of hMSC are associated with DLK1-induced cytokine expression. Furthermore, DLK1 promoted B cell proliferation, synergized the immune response effects of the bacterial endotoxin lipopolysaccharide on hMSC, and led to marked transactivation of the NF-κB. Our data suggest a new role for DLK1 in regulating the multiple biological functions of hMSC by influencing the composition of their microenvironment “niche.” Our findings also demonstrate a role for DLK1 in mediating the immune response.