c-Jun is a negative regulator of myelination

Schwann cell myelination depends on Krox-20/Egr2 and other promyelin transcription factors that are activated by axonal signals and control the generation of myelin-forming cells. Myelin-forming cells remain remarkably plastic and can revert to the immature phenotype, a process which is seen in injured nerves and demyelinating neuropathies. We report that c-Jun is an important regulator of this plasticity. At physiological levels, c-Jun inhibits myelin gene activation by Krox-20 or cyclic adenosine monophosphate. c-Jun also drives myelinating cells back to the immature state in transected nerves in vivo. Enforced c-Jun expression inhibits myelination in cocultures. Furthermore, c-Jun and Krox-20 show a cross-antagonistic functional relationship. c-Jun therefore negatively regulates the myelinating Schwann cell phenotype, representing a signal that functionally stands in opposition to the promyelin transcription factors. Negative regulation of myelination is likely to have significant implications for three areas of Schwann cell biology: the molecular analysis of plasticity, demyelinating pathologies, and the response of peripheral nerves to injury

A Central Role for the ERK-Signaling Pathway in Controlling Schwann Cell Plasticity and Peripheral Nerve Regeneration In Vivo

SummaryFollowing damage to peripheral nerves, a remarkable process of clearance and regeneration takes place. Axons downstream of the injury degenerate, while the nerve is remodeled to direct axonal regrowth. Schwann cells are important for this regenerative process. “Sensing” damaged axons, they dedifferentiate to a progenitor-like state, in which they aid nerve regeneration. Here, we demonstrate that activation of an inducible Raf-kinase transgene in myelinated Schwann cells is sufficient to control this plasticity by inducing severe demyelination in the absence of axonal damage, with the period of demyelination/ataxia determined by the duration of Raf activation. Remarkably, activation of Raf-kinase also induces much of the inflammatory response important for nerve repair, including breakdown of the blood-nerve barrier and the influx of inflammatory cells. This reversible in vivo model identifies a central role for ERK signaling in Schwann cells in orchestrating nerve repair and is a powerful system for studying peripheral neuropathies and cancer

Health-related quality of life after treatment for bladder cancer in England

Background Little is known about quality of life after bladder cancer treatment. This common cancer is managed using treatments that can affect urinary, sexual and bowel function. Methods To understand quality of life and inform future care, the Department of Health (England) surveyed adults surviving bladder cancer 1–5 years after diagnosis. Questions related to disease status, co-existing conditions, generic health (EQ-5D), cancer-generic (Social Difficulties Inventory) and cancer-specific outcomes (Functional Assessment of Cancer Therapy—Bladder). Results In total, 673 (54%) patients responded; including 500 (74%) men and 539 (80%) with co-existing conditions. Most respondents received endoscopic treatment (60%), while 92 (14%) and 99 (15%) received radical cystectomy or radiotherapy, respectively. Questionnaire completion rates varied (51–97%). Treatment groups reported ≥1 problem using EQ-5D generic domains (59–74%). Usual activities was the most common concern. Urinary frequency was common after endoscopy (34–37%) and radiotherapy (44–50%). Certain populations were more likely to report generic, cancer-generic and cancer-specific problems; notably those with co-existing long-term conditions and those treated with radiotherapy. Conclusion The study demonstrates the importance of assessing patient-reported outcomes in this population. There is a need for larger, more in-depth studies to fully understand the challenges patients with bladder cancer face

A Genetic Screen for Anchorage-Independent Proliferation in Mammalian Cells Identifies a Membrane-Bound Neuregulin

Anchorage-independent proliferation is a hallmark of oncogenic transformation and is thought to be conducive to proliferation of cancer cells away from their site of origin. We have previously reported that primary Schwann cells expressing the SV40 Large T antigen (LT) are not fully transformed in that they maintain a strict requirement for attachment, requiring a further genetic change, such as oncogenic Ras, to gain anchorage-independence. Using the LT-expressing cells, we performed a genetic screen for anchorage-independent proliferation and identified Sensory and Motor Neuron Derived Factor (SMDF), a transmembrane class III isoform of Neuregulin 1. In contrast to oncogenic Ras, SMDF induced enhanced proliferation in normal primary Schwann cells but did not trigger cellular senescence. In cooperation with LT, SMDF drove anchorage-independent proliferation, loss of contact inhibition and tumourigenicity. This transforming ability was shared with membrane-bound class III but not secreted class I isoforms of Neuregulin, indicating a distinct mechanism of action. Importantly, we show that despite being membrane-bound signalling molecules, class III neuregulins transform via a cell intrinsic mechanism, as a result of constitutive, elevated levels of ErbB signalling at high cell density and in anchorage-free conditions. This novel transforming mechanism may provide new targets for cancer therapy

NF1 loss disrupts Schwann cell–axonal interactions: a novel role for semaphorin 4F

Neurofibromatosis type 1 (NF1) patients develop neurofibromas, tumors of Schwann cell origin, as a result of loss of the Ras-GAP neurofibromin. In normal nerves, Schwann cells are found tightly associated with axons, while loss of axonal contact is a frequent and important early event in neurofibroma development. However, the molecular basis of this physical interaction or how it is disrupted in cancer remains unclear. Here we show that loss of neurofibromin in Schwann cells is sufficient to disrupt Schwann cell/axonal interactions via up-regulation of the Ras/Raf/ERK signaling pathway. Importantly, we identify down-regulation of semaphorin 4F (Sema4F) as the molecular mechanism responsible for the Ras-mediated loss of interactions. In heterotypic cocultures, Sema4F knockdown induced Schwann cell proliferation by relieving axonal contact-inhibitory signals, providing a mechanism through which loss of axonal contact contributes to tumorigenesis. Importantly, Sema4F levels were strongly reduced in a panel of human neurofibromas, confirming the relevance of these findings to the human disease. This work identifies a novel role for the guidance-molecules semaphorins in the mediation of Schwann cell/axonal interactions, and provides a molecular mechanism by which heterotypic cell–cell contacts control cell proliferation and suppress tumorigenesis. Finally, it provides a new approach for the development of therapies for NF1

Comparative methylome analysis of benign and malignant peripheral nerve sheath tumors

Aberrant DNA methylation (DNAm) was first linked to cancer over 25 yr ago. Since then, many studies have associated hypermethylation of tumor suppressor genes and hypomethylation of oncogenes to the tumorigenic process. However, most of these studies have been limited to the analysis of promoters and CpG islands (CGIs). Recently, new technologies for whole-genome DNAm (methylome) analysis have been developed, enabling unbiased analysis of cancer methylomes. By using MeDIP-seq, we report a sequencing-based comparative methylome analysis of malignant peripheral nerve sheath tumors (MPNSTs), benign neurofibromas, and normal Schwann cells. Analysis of these methylomes revealed a complex landscape of DNAm alterations. In contrast to what has been reported for other tumor types, no significant global hypomethylation was observed in MPNSTs using methylome analysis by MeDIP-seq. However, a highly significant (P < 10−100) directional difference in DNAm was found in satellite repeats, suggesting these repeats to be the main target for hypomethylation in MPNSTs. Comparative analysis of the MPNST and Schwann cell methylomes identified 101,466 cancer-associated differentially methylated regions (cDMRs). Analysis showed these cDMRs to be significantly enriched for two satellite repeat types (SATR1 and ARLα) and suggests an association between aberrant DNAm of these sequences and transition from healthy cells to malignant disease. Significant enrichment of hypermethylated cDMRs in CGI shores (P < 10−60), non–CGI-associated promoters (P < 10−4) and hypomethylated cDMRs in SINE repeats (P < 10−100) was also identified. Integration of DNAm and gene expression data showed that the expression pattern of genes associated with CGI shore cDMRs was able to discriminate between disease phenotypes. This study establishes MeDIP-seq as an effective method to analyze cancer methylomes

(A) Western blot showing that c-Jun is absent from cells infected with CRE-expressing adenovirus

The blot also compares periaxin in control (Con) and –null cells (CRE) infected with GFP control adenovirus (GFP) or a Krox-20/GFP virus (K20). Note high periaxin levels in Krox-20–infected –null cells (CRE). (B–E) control ( con) and –null mouse Schwann cells 2 d after infection with Krox-20/GFP adenovirus. Note that Krox-20 induces much higher levels of P protein in –null cells (D and E) than in control cells (B and C). The reason why P levels in the Krox-20–expressing control cells appear low in this picture (C) compared with other comparable experiments (e.g., ) is that exposure had to be reduced (equally for C and E) to avoid overexposure in E. (F and G) P protein expression in control cells P ( con) and c–null mouse Schwann cells after 3 d of exposure to db-cAMP/NRG-1. Note that cAMP/NRG-1 induces substantially higher P levels in cells without c-Jun. Bars, 15 μm.<p><b>Copyright information:</b></p><p>Taken from "c-Jun is a negative regulator of myelination"</p><p></p><p>The Journal of Cell Biology 2008;181(4):625-637.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2386103.</p><p></p

(A and B) Cotransfection of Krox-20/GFP with Jun(Asp) or with Jun(Ala) inhibits Krox-20–mediated induction of periaxin and P

K20/EV represents cells cotransfected with Krox-20 and control vector. (C–F) P in situ experiment showing that cotransfection of Krox-20/GFP with Jun(Ala) inhibits Krox-20–mediated induction of mRNA. C and D are controls, and the arrows show a cell coexpressing Krox-20 and a control vector where Krox-20 has induced P mRNA. Arrows in E and F show a cell coexpressing Krox-20 and Jun(Ala) where Jun(Ala) has inhibited Krox-induced expression. Bar, 15 μm. (G) Percentages of GFP-positive cells that also express mRNA in cells cotransfected with the constructs indicated. Error bars show one standard deviation of the mean.<p><b>Copyright information:</b></p><p>Taken from "c-Jun is a negative regulator of myelination"</p><p></p><p>The Journal of Cell Biology 2008;181(4):625-637.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2386103.</p><p></p

(A and B) Cells cotransfected with empty GFP vector (to visualize transfected cells) and an empty control vector (EV; A) or a vector (B)

Both cultures were then treated with 1 mM db-cAMP for 2 d to induce Krox-20 and were immunolabeled for Krox-20. In A, arrows point to induced Krox-20 in nuclei of GFP-positive control cells (yellow nuclei of Krox-20–positive GFP-positive cells). In B, no Krox-20 is induced (arrows) in cells containing . Arrowheads in both panels indicate untransfected cells that have been induced to express Krox-20 by db-cAMP as controls for induction. (C) Activation of JNK inhibits induction of Krox-20. Western blot of cells infected with adenovirus expressing control LacZ or virus expressing activated MKK7 to activate JNK is shown. Note that the Krox-20 and periaxin induced by 2 d of exposure to 1 mM db-cAMP in LacZ control cells is inhibited by MKK7 expression. Note also that MKK7 elevates c-Jun in the presence of db-cAMP. (D–G) In –null cells, loss of Krox-20 expression is significantly delayed. Double immunolabeling of control cells (D and E) and –null cells (F and G) for Krox-20 (red) and periaxin (green) after 2 d in culture in DM containing 20 ng/ml NRG-1 is shown. Note that Krox-20 has disappeared from the control cells, whereas many –null cells still have Krox-20–positive nuclei (G, arrows). Note that –null Krox-20–positive cells are also periaxin positive (F, arrows), whereas control cells have lost periaxin expression (D). Bars, 15 μm.<p><b>Copyright information:</b></p><p>Taken from "c-Jun is a negative regulator of myelination"</p><p></p><p>The Journal of Cell Biology 2008;181(4):625-637.</p><p>Published online 19 May 2008</p><p>PMCID:PMC2386103.</p><p></p