Dissecting the roles of glia-specific Sigma-1 receptors in chronic inflammatory CNS disease

• Applicant: Professor Dr. Frank Kirchhoff
• Subject Area: Experimental Models for the Understanding of Nervous System Diseases ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2018 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 391625006

• Final Report Year: 2022

Final Report Abstract

We, the combined teams at the University of Saarland, USAAR, and the Southeast University, SEU (Honghong Yao) in Nanjing joined our interests and efforts in studying the functions of glial Sigma-1 receptors (Sig1Rs) regulating neuroinflammation. Using constitutive Sig1R knockout (KO) mice provided by the SEU group, we developed a novel immunohistochemical (IHC) protocol to specifically detect Sig1Rs in the central nervous system (CNS). For the fundamental experiment of the whole project, i.e. establishing cell-type specific Sig1R deficient mouse models, we generated two Sig1R flox mouse lines. Using the first Sig1R flox mouse in which all four exons of the sigmar1 gene were flanked by two loxP sites, we found an unexpected long-term existence of extrachromosomal circular DNA (eccDNA) generated from the Cre-excised loxP-flanked segment. Such eccDNA formed in the first Sig1R flox mice led to continuous expression of Sig1R protein in post-mitotic Cre-expressing cells. Subsequently, we generated the second Sig1R flox mice by flanking exon 1-3 with loxP sites. Using the newly established specific IHC method, we were able to show a drastic reduction of Sig1R expression in pyramidal neurons in the second Sig1R flox mice with neuronal Cre expression (NEX-Cre), indicating a successful achievement of cell-type specific deletion of Sig1Rs. We also crossbred the second Sig1R flox mouse line to other glia-specific Cre-expressing mouse lines (NG2-CreERT2, CX3CR1-CreERT2, and GLAST-CreERT2) to ablate Sig1Rs in different glial cells. The systematic analysis of these novel glia-specific Sig1R conditional KO mice is still ongoing based on our established research paradigms for glia development, CNS diseases, as well as protein-protein interactions (e.g. between L-type voltagegated Ca2+ channels and Sig1R).

Publications

• (2019) Amyloid β oligomers constrict human capillaries in Alzheimer's disease via signaling to pericytes. Science 19;365(6450)
  Nortley, Ross; Korte, Nils; Izquierdo, Pablo; Hirunpattarasilp, Chanawee; Mishra, Anusha; Jaunmuktane, Zane; Kyrargyri, Vasiliki; Pfeiffer, Thomas; Khennouf, Lila; Madry, Christian; Gong, Hui; Richard-Loendt, Angela; Huang, Wenhui; Saito, Takashi; Saido, Takaomi C.; Brandner, Sebastian; Sethi, Huma & Attwell, David
  
• (2019) Early embryonic NG2 glia are exclusively gliogenic and do not generate neurons in the brain. Glia 67(6):1094-1103
  Huang, Wenhui; Guo, Qilin; Bai, Xianshu; Scheller, Anja & Kirchhoff, Frank
  
• (2020) Acute brain injuries trigger microglia as an additional source of the proteoglycan NG2. Acta Neuropathol Commun 8(1):146
  Huang, Wenhui; Bai, Xianshu; Meyer, Erika & Scheller, Anja
  
• (2021) L-type Ca2+ channels of NG2-glia determine proliferation and NMDA receptor-dependent plasticity. Front Cell Dev Biol
  Zhao, Na; Huang, Wenhui; Cãtãlin, Bogdan; Scheller, Anja & Kirchhoff, Frank
  
• (2021) Pen-2 Negatively Regulates the Differentiation of Oligodendrocyte Precursor Cells into Astrocytes in the Central Nervous System. J Neurosci 41:4976-4990
  Hou, Jinxing; Bi, Huiru; Ye, Zhuoyang; Huang, Wenhui; Zou, Gang; Zou, Xiaochuan; Shi, Yun Stone; Shen, Ying; Ma, Quanhong; Kirchhoff, Frank; Hu, Yimin & Chen, Guiquan
  
• (2021) Progenies of NG2 glia: what do we learn from transgenic mouse models? Neural Regen Res 16(1):43-48
  Huang, Wenhui; Guo, Qilin & Scheller, Anja
  
• (2022) Specific detection and deletion of the sigma-1 receptor widely expressed in neurons and glial cells in vivo. Journal of Neurochemistry, 2022, Early View.
  Liu Q., Guo Q., Fang L.P., Yao H., Scheller A., Kirchhoff F., Huang W.