TWEAK regulates proliferation and differentiation of adult neural progenitor cells Marion N. Schölzke a,b , Amely Röttinger a , Sasidhar Murikinati a , Nadine Gehrig a , Christoph Leib a , Markus Schwaninger a, ⁎ a Department of Pharmacology, University of Heidelberg, Germany b Department of Neurology, University of Heidelberg, Germany abstract article info Article history: Received 12 August 2010 Revised 6 October 2010 Accepted 21 October 2010 Available online 30 October 2010 Keywords: Adult neurogenesis TWEAK Fn14 NF-κB hes1 Subventricular zone The cytokine TWEAK is expressed in the brain and is induced in cerebral ischemia and other brain disorders. TWEAK regulates proliferation and differentiation of progenitor cells but its effect on adult neural progenitor cells is still unknown. Therefore, we investigated the proliferation of neural progenitor cells from the subventricular zone of adult mice in response to TWEAK treatment. TWEAK inhibited proliferation of neural progenitor cells through its membrane receptor Fn14. The reduced proliferation was not due to cell death. By using a reporter assay we found that TWEAK activated the transcription factor NF-κB in adult neural progenitor cells. Blockade of NF-κB signaling reversed the inhibition of cell proliferation by TWEAK. In addition, TWEAK induced neuronal differentiation of neural progenitor cells and lowered the expression of hes1, a transcription factor that prevents neuronal differentiation. In adult mice deficient of the TWEAK receptor Fn14, neurogenesis was reduced in the subventricular zone. In conclusion, our data show that TWEAK regulates adult neurogenesis in the subventricular zone by binding to the membrane receptor Fn14 and activating NF-κB. © 2010 Elsevier Inc. All rights reserved. Introduction TNF-like weak inducer of apoptosis (TWEAK) is a member of the TNF family of cytokines and binds to the membrane receptor Fn14, a member of the TNF receptor superfamily (Winkles, 2008). TWEAK was originally named after its pro-apoptotic activity (Chicheportiche et al., 1997) but soon other properties were described as well. TWEAK affects cell proliferation, migration, differentiation, and survival (Winkles, 2008). Moreover, several lines of evidence suggest that TWEAK plays an important role in tissue repair (Burkly et al., 2007). It is a potent pro- angiogenic and pro-inflammatory agent (Winkles, 2008) and TWEAK can enhance tissue regeneration. According to published reports, it also stimulates the proliferation of liver progenitor cells in models of liver injury (Jakubowski et al., 2005; Tirnitz-Parker et al., 2010). In skeletal muscle, Fn14-deficient mice exhibit delayed muscle regeneration after injury, consistent with TWEAK's ability to stimulate the proliferation of myoblasts and inhibit their differentiation (Girgenrath et al., 2006). During development, age-dependent effects of TWEAK on proliferation and differentiation of neural progenitor cells (NPC) were reported (Hamill et al., 2007). In this study, TWEAK inhibited the proliferation of postnatal day 1 NPC but had no effect on E12 NPC. In contrast, TWEAK induced neurite outgrowth of E12 but not in P1 progenitor cells. The effect of TWEAK on adult neural progenitor cells is unknown but potentially of interest because TWEAK is expressed in the adult brain by neurons and astrocytes. Furthermore, TWEAK and its receptor Fn14 are up-regulated in the context of cerebral ischemia and experimental autoimmune encephalomyelitis, a model of multiple sclerosis (Desplat- Jego et al., 2002; Inta et al., 2008; Potrovita et al., 2004). Neurogenesis persists in two areas of the adult brain, the subventricular zone (SVZ) and the subgranular zone of the dentate gyrus. Because an increase in neurogenesis after stroke and other brain injuries may contribute to recovery, there is considerable interest in how neurogenesis is regulated (Lindvall and Kokaia, 2008). So far, neurogenesis has been linked to spatial learning and odor discrimination (Clelland et al., 2009; Gheusi et al., 2000; Zhang et al., 2008) but many questions concerning the function of neurogenesis in the normal and injured brain remain to be answered. In order to characterize the role of the TWEAK/Fn14 pathway in the regulation of adult neurogenesis we have investigated its effect on adult NPC in vitro. TWEAK inhibited the proliferation of adult progenitor cells and stimulated their neuronal differentiation. The reduced proliferation upon TWEAK treatment is mediated by the transcription factor NF-κB. A lower number of newborn neuroblasts in the SVZ of Fn14 -/- mice suggests that the TWEAK-Fn14 axis is important for regulating adult neurogenesis in vivo. Molecular and Cellular Neuroscience 46 (2011) 325–332 Abbreviations: BrdU, bromodeoxyuridine; DCX, doublecortin; Fn14, fibroblast growth factor inducible 14; IKK, IκB kinase; NPC, neural progenitor cell; PFA, paraformaldehyde; SVZ, subventricular zone; TNF, tumor necrosis factor; TWEAK, TNF-like weak inducer of apoptosis. ⁎ Corresponding author. Department of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany. Fax: + 49 6221 548367. E-mail address: markus.schwaninger@pharma.uni-heidelberg.de (M. Schwaninger). 1044-7431/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.mcn.2010.10.004 Contents lists available at ScienceDirect Molecular and Cellular Neuroscience journal homepage: www.elsevier.com/locate/ymcne