Fas ligand (FasL, Apo-1L) is a member of the tumor necrosis factor protein family and binding to its receptor (Fas, Apo-1, CD95) triggers cell death through apoptosis. Ligand expression is restricted ...to cells with known cytolytic activity and found on hematopoietic cells of the T cell and natural killer lineage. Here we provide evidence that B lymphocytes can express FasL. Flow cytometric analysis revealed that FasL is expressed on the surface of B cells upon stimulation with either lipopolysaccharide or phorbol 12-myristate 13-acetate/ionomycin. FasL expression on activated B cells was confirmed by western blot and reverse transcriptase polymerase chain reaction analysis. FasL on B cells is functional since lipopolysaccharide-activated B lymphocytes derived from wild type, but not from gld mutant mice, were able to kill Fas-sensitive target cells. Our data suggest that the Fas system may contribute to the control of B cell homeostasis.
Exercise is a potent skeletal muscle stimulus and one of the most effective strategies to prevent muscle loss and type 2 diabetes. Biological sex-based differences are reported for aerobic capacity, ...muscle mass, and exercise performance. We aimed to provide a yet missing comprehensive picture of molecular differences between female and male skeletal muscle at baseline, after acute exercise and training. Further we investigated which differences were conserved in vitro. We characterized muscle biopsies from 25 (16f/9m) subjects in a multi-omics approach employing epigenomics, transcriptomics and proteomics at baseline, after acute exercise and 8 weeks of supervised endurance training. Donor matched myoblasts and myotubes were analyzed in vitro. We found differential CpG-site methylation in 16.012 genes, 1.366 differentially expressed genes and 120 proteins at baseline. Differential transcripts were associated with translational regulation, histone methylation, glucose homeostasis and insulin signaling. Type-2 fast-twitch fiber-type proteins were elevated in males, along with proteins regulating glycolysis. Y-linked transcript expression was conserved in vitro, but only a few differences in expression of autosomal genes, e.g. elevated LDHB in females. Acute exercise upregulated oxidative stress-responsive transcripts predominantly in males. After 8-week-training, both sexes had upregulated mitochondrial proteins involved in substrate oxidation and ATP production, while glycolytic fiber marker MYH1 and MYH3 were only reduced in males. Thus, sex specific differences exist in resting skeletal muscle and in exercise adaptation on epigenomic, transcriptomic and proteomic level. The few conserved differences in vitro hint towards hormonal or yet undefined mechanisms. Training might mitigate initially differential responses to exercise. The question remains whether there are sex specific differences within individual fiber-types or whether it is just a matter of composition. Disclosure S.I. Dreher: None. T. Goj: None. C. von Toerne: None. M. Hoene: None. M. Irmler: None. M. Ouni: None. M. Jähnert: None. J. Beckers: None. A. Peter: None. A.L. Birkenfeld: None. A. Schürmann: None. S.M. Hauck: None. C. Weigert: None.
Numerous transcriptional regulators of neurogenesis have been identified in the developing and adult brain, but how neurogenic fate is programmed at the epigenetic level remains poorly defined. Here, ...we report that the transcription factor Pax6 directly interacts with the Brg1-containing BAF complex in adult neural progenitors. Deletion of either Brg1 or Pax6 in the subependymal zone (SEZ) causes the progeny of adult neural stem cells to convert to the ependymal lineage within the SEZ while migrating neuroblasts convert to different glial lineages en route to or in the olfactory bulb (OB). Genome-wide analyses reveal that the majority of genes downregulated in the Brg1 null SEZ and OB contain Pax6 binding sites and are also downregulated in Pax6 null SEZ and OB. Downstream of the Pax6-BAF complex, we find that Sox11, Nfib, and Pou3f4 form a transcriptional cross-regulatory network that drives neurogenesis and can convert postnatal glia into neurons. Taken together, elements of our work identify a tripartite effector network activated by Pax6-BAF that programs neuronal fate.
Display omitted
•Pax6 forms a complex with Brg1-containing BAF in adult neural stem cells•Loss of either Pax6 or Brg1 converts neuronal progenitors to glia or ependymal cells•Nfib, Sox11, and Pou3f4 form a cross-regulatory network downstream of Pax6-BAF•Cross-regulatory network drives neurogenesis and converts glia into neurons
A Pax6-BAF complex programs neuronal fate in progenitors by activating a Sox11, Nfib, and Pou3f4 cross-regulatory network.
A detailed understanding of intestinal stem cell (ISC) self-renewal and differentiation is required to treat chronic intestinal diseases. However, the different models of ISC lineage hierarchy
and ...segregation
are subject to debate. Here, we have discovered non-canonical Wnt/planar cell polarity (PCP)-activated ISCs that are primed towards the enteroendocrine or Paneth cell lineage. Strikingly, integration of time-resolved lineage labelling with single-cell gene expression analysis revealed that both lineages are directly recruited from ISCs via unipotent transition states, challenging the existence of formerly predicted bi- or multipotent secretory progenitors
. Transitory cells that mature into Paneth cells are quiescent and express both stem cell and secretory lineage genes, indicating that these cells are the previously described Lgr5
label-retaining cells
. Finally, Wnt/PCP-activated Lgr5
ISCs are molecularly indistinguishable from Wnt/β-catenin-activated Lgr5
ISCs, suggesting that lineage priming and cell-cycle exit is triggered at the post-transcriptional level by polarity cues and a switch from canonical to non-canonical Wnt/PCP signalling. Taken together, we redefine the mechanisms underlying ISC lineage hierarchy and identify the Wnt/PCP pathway as a new niche signal preceding lateral inhibition in ISC lineage priming and segregation.
According to the current consensus, murine neural stem cells (NSCs) apically contacting the lateral ventricle generate differentiated progenitors by rare asymmetric divisions or by relocating to the ...basal side of the ventricular–subventricular zone (V‐SVZ). Both processes will ultimately lead to the generation of adult‐born olfactory bulb (OB) interneurons. In contrast to this view, we here find that adult‐born OB interneurons largely derive from an additional NSC‐type resident in the basal V‐SVZ. Despite being both capable of self‐renewal and long‐term quiescence, apical and basal NSCs differ in Nestin expression, primary cilia extension and frequency of cell division. The expression of Notch‐related genes also differs between the two NSC groups, and Notch activation is greatest in apical NSCs. Apical downregulation of Notch‐effector Hes1 decreases Notch activation while increasing proliferation across the niche and neurogenesis from apical NSCs. Underscoring their different roles in neurogenesis, lactation‐dependent increase in neurogenesis is paralleled by extra activation of basal but not apical NSCs. Thus, basal NSCs support OB neurogenesis, whereas apical NSCs impart Notch‐mediated lateral inhibition across the V‐SVZ.
Synopsis
Basal neural stem cells are the most abundant stem cell type in the adult mouse V‐SVZ from birth onwards and the main contributors to olfactory bulb neurogenesis.
Basal NSCs do not contact the lateral ventricle unlike the apical radial glia‐like counterpart.
Basal NSCs are the main source of adult‐born olfactory bulb interneurons.
Apical NSCs regulate niche proliferation by promoting Notch‐mediated lateral inhibition of proliferation.
Basal neural stem cells are the most abundant stem cell type in the adult mouse V‐SVZ from birth onwards and the main contributors to olfactory bulb neurogenesis.
Exercise training is known to improve glucose tolerance and reverse insulin resistance in people with obesity. However, some individuals fail to improve or even decline in their clinical traits ...following exercise intervention.
This study focused on gene expression and DNA methylation signatures in skeletal muscle of low (LRE) and high responders (RES) to 8 weeks of supervised endurance training.
We performed skeletal muscle gene expression and DNA methylation analyses in LRE and RES before and after exercise intervention. Additionally, we applied the least absolute shrinkage and selection operator (LASSO) approach to identify predictive marker genes of exercise outcome.
We show that the two groups differ markedly already before the intervention. RES were characterized by lower expression of genes involved in DNA replication and repair, and higher expression of extracellular matrix (ECM) components. The LASSO approach identified several novel candidates (eg, ZCWPW2, FOXRED1, STK40) that have not been previously described in the context of obesity and exercise response. Following the intervention, LRE reacted with expression changes of genes related to inflammation and apoptosis, RES with genes related to mitochondrial function. LRE exhibited significantly higher expression of ECM components compared to RES, suggesting improper remodeling and potential negative effects on insulin sensitivity. Between 45% and 70% of differences in gene expression could be linked to differences in DNA methylation.
Together, our data offer an insight into molecular mechanisms underlying differences in response to exercise and provide potential novel markers for the success of intervention.
Resistance to insulin and insulin-like growth factor 1 (IGF1) in pancreatic β-cells causes overt diabetes in mice; thus, therapies that sensitize β-cells to insulin may protect patients with diabetes ...against β-cell failure
. Here we identify an inhibitor of insulin receptor (INSR) and IGF1 receptor (IGF1R) signalling in mouse β-cells, which we name the insulin inhibitory receptor (inceptor; encoded by the gene Iir). Inceptor contains an extracellular cysteine-rich domain with similarities to INSR and IGF1R
, and a mannose 6-phosphate receptor domain that is also found in the IGF2 receptor (IGF2R)
. Knockout mice that lack inceptor (Iir
) exhibit signs of hyperinsulinaemia and hypoglycaemia, and die within a few hours of birth. Molecular and cellular analyses of embryonic and postnatal pancreases from Iir
mice showed an increase in the activation of INSR-IGF1R in Iir
pancreatic tissue, resulting in an increase in the proliferation and mass of β-cells. Similarly, inducible β-cell-specific Iir
knockout in adult mice and in ex vivo islets led to an increase in the activation of INSR-IGF1R and increased proliferation of β-cells, resulting in improved glucose tolerance in vivo. Mechanistically, inceptor interacts with INSR-IGF1R to facilitate clathrin-mediated endocytosis for receptor desensitization. Blocking this physical interaction using monoclonal antibodies against the extracellular domain of inceptor resulted in the retention of inceptor and INSR at the plasma membrane to sustain the activation of INSR-IGF1R in β-cells. Together, our findings show that inceptor shields insulin-producing β-cells from constitutive pathway activation, and identify inceptor as a potential molecular target for INSR-IGF1R sensitization and diabetes therapy.
Summary
T‐helper cell type 17 (Th17) mediated inflammation is associated with various diseases including autoimmune encephalitis, inflammatory bowel disease and lung diseases such as chronic ...obstructive pulmonary disease and asthma. Differentiation into distinct T helper subtypes needs to be tightly regulated to ensure an immunological balance. As microRNAs (miRNAs) are critical regulators of signalling pathways, we aimed to identify specific miRNAs implicated in controlling Th17 differentiation. We were able to create a regulatory network model of murine T helper cell differentiation by combining Affymetrix mRNA and miRNA arrays and in silico analysis. In this model, the miR‐212~132 and miR‐182~183 clusters were significantly up‐regulated upon Th17 differentiation, whereas the entire miR‐106~363 cluster was down‐regulated and predicted to target well‐known Th17 cell differentiation pathways. In vitro transfection of miR‐18b, miR‐106a and miR‐363‐3p into primary murine Cd4+ lymphocytes decreased expression of retinoid‐related orphan receptor c (Rorc), Rora, Il17a and Il17f, and abolished secretion of Th17‐mediated interleukin‐17a (Il17a). Moreover, we demonstrated target site‐specific regulation of the Th17 transcription factors Rora and nuclear factor of activated T cells (Nfat) 5 by miR‐18b, miR‐106a and miR‐363‐3p through luciferase reporter assays. Here, we provide evidence that miRNAs are involved in controlling the differentiation and function of T helper cells, offering useful tools to study and modify Th17‐mediated inflammation.
By combining mRNA and miRNA microarray analysis of in vitro differentiated T helper type 2 (Th2) and Th17 cells, we generated an in silico regulatory network model or Th cell differentiation. Further, we identified miR‐18b, miR‐106a and miR‐363‐3p to specifically target Th17 transcription factors Rora, Nfat5 and Rorc and thus to be involved in Th17 differentiation and function. Here, we provide evidence that miRNAs are involved in controlling the differentiation and function of T helper cells, offering useful tools to study and modify Th17‐mediated inflammation.
Stem cell senescence is considered deleterious because it may impair tissue renewal and function. On the other hand, senescence may arrest the uncontrolled growth of transformed stem cells and ...protect organisms from cancer. This double function of senescence is strictly linked to the activity of genes that the control cell cycle such as the retinoblastoma proteins RB1, RB2/P130, and P107. We took advantage of the RNA interference technique to analyze the role of these proteins in the biology of mesenchymal stem cells (MSC). Cells lacking RB1 were prone to DNA damage. They showed elevated levels of p53 and p21
cip1
and increased regulation of RB2/P130 and P107 expression. These cells gradually adopted a senescent phenotype with impairment of self-renewal properties. No significant modification of cell growth was observed as it occurs in other cell types or systems. In cells with silenced RB2/P130, we detected a reduction of DNA damage along with a higher proliferation rate, an increase in clonogenic ability, and the diminution of apoptosis and senescence. Cells with silenced RB2/P130 were cultivated for extended periods of time without adopting a transformed phenotype. Of note, acute lowering of P107 did not induce relevant changes in the in vitro behavior of MSC. We also analyzed cell commitment and the osteo-chondro-adipogenic differentiation process of clones derived by MSC cultures. In all clones obtained from cells with silenced retinoblastoma genes, we observed a reduction in the ability to differentiate compared with the control clones. In summary, our data show evidence that the silencing of the expression of RB1 or RB2/P130 is not compensated by other gene family members, and this profoundly affects MSC functions.
PDF
