Neuroscience Letters 455 (2009) 46–50 Contents lists available at ScienceDirect Neuroscience Letters journal homepage: www.elsevier.com/locate/neulet Reduced Morg1 expression in ischemic human brain Daniela Haase a , Silke Keiner b , Christian Mawrin a,c,∗ , Gunter Wolf d a Department of Neuropathology, Friedrich-Schiller-University Jena, Germany b Department of Neurology, Friedrich-Schiller-University Jena, Germany c Department of Neuropathology, Otto-von-Guericke-University Magdeburg, Germany d Department of Internal Medicine III, Friedrich-Schiller-University Jena, Germany article info Article history: Received 17 December 2008 Received in revised form 11 March 2009 Accepted 13 March 2009 Keywords: Morg1 Brain Ischemia HIF-1 abstract The mitogen-activated protein kinase organizer 1 (Morg1) has been recently identified as modular scaffold regulating ERK signaling. Morg1 also attenuates expression of the hypoxia-inducible factor-1 (HIF-1) by activating or stabilizing of prolyl-hydroxylase 3 (PHD3). Here we demonstrate for the first time that Morg1 is expressed in the human brain in neurons, glial cells, and blood vessel walls. Immunohistochemistry, RT real-time PCR and western blotting indicated that Morg1 expression is reduced in human brain tissue with ischemic damage. Moreover, reactive astrocytes in the surrounding brain tissue showed strong Morg1 expression. Since hypoxic adaptation with enhancing HIF-1 expression can engage a genetic program leading to profound sparing of brain tissue and enhanced recovery of function, down-regulation of Morg1 expression in the ischemic brain may be viewed as an intrinsic mechanism to stimulate this response. On the other hand, upregulation of Morg1 in astrocytes surrounding the penumbra may counteract this hypoxic adaptation. © 2009 Elsevier Ireland Ltd. All rights reserved. The brain demands continuously oxygen to fulfill its high complex and diverse functions. Stroke has emerged as a leading cause of disability and is characterized by reduced perfusion and oxygen delivery to brain tissue. However, the brain utilizes homeostatic strategies to fight hypoxia and ischemia [11]. Although the mecha- nistic basis of ischemic tolerance has not been fully understood, several lines of evidence suggest that the transcription factor hypoxia-inducible factor-1 (HIF-1) mediates the activation of many genes involved in the adaptation of surviving brain tissue after stroke [10,11]. For example, HIF-1 levels are increased after focal and global brain ischemia [2,3,14]. HIF-1 has been also implicated in exhibiting neuroprotective gene expression after hypoxic pre- conditioning [11]. One subunit of the dimer HIF is HIF-1 that is continuously expressed in the cell but immediately degraded via the proteasomal pathway after ubiquitination. In the pres- ence of oxygen, prolyl residues in HIF-1 are hydroxylated by the enzymes prolyl-hydroxylase domain (PHD) 1–3. Inhibition of PHDs, for example by treatment with desferoxamine or cobalt chlo- ride resulted in reduced neuron loss in models of focal or global ischemia [1,4,9]. We recently identified a novel WD-repeat protein designated Morg1 (MAPK organizer 1) that interacts with PHD3 in vitro and in vivo [5]. Binding to PHD3 occurs at a conserved ∗ Corresponding author at: Department of Neuropathology, Otto-von-Guericke- University Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany. Tel.: +49 391 671 5825; fax: +49 391 671 3300. E-mail address: christian.mawrin@med.ovgu.de (C. Mawrin). region predicted to the top surface of one propeller blade. HIF- 1 expression is reduced by Morg1 because this protein activates or stabilizes PHD3, leading to an accelerated degradation of HIF- 1 [5]. Although Morg1 was from a murine cDNA library by yeast two-hybrid assays, no information is available regarding Morg1 expression in the human brain and its potential regulation after ischemia. Brain tissue derived at autopsy from five cases and from open biopsy for suspected brain tumor (one case) was used in the present study. Clinicopathological data of these cases are given in Table 1. From all cases with ischemic brain damage (except case no. 6), tissue from the side of infarction and from the contralateral hemisphere serving as control tissue was removed after cutting of the unfixed brain and snap-frozen in liquid nitrogen and stored at −80 ◦ C until further processing. Corresponding samples from infarction site, as well as from the contralateral hemisphere were formalin-fixed and paraffin-embedded using standard procedures. Diagnostic H&E sections were evaluated to assess the stage of the ischemic brain damage. From case no. 6, only paraffin-embedded brain tissue was available. For immunohistochemistry, 4-m thick sections were deparaf- finized with xylene for 15min and rehydrated through a series of graded alcohols. Sections were pretreated in a microwave oven using 0.01 M citrate buffer (pH 6.0) for 3 × 10 min. Endogenous peroxidase activity was blocked by incubation (30min) in 0.3% H 2 O 2 in methanol. The sections were gently rinsed with TBS buffer and then incubated with bovine serum albumin for 30 min to reduce non-specific antibody binding. Sections were incubated at 0304-3940/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2009.03.048