Accelerated Hippocampal Spreading Depression and Enhanced Locomotory Activity in Mice with Astrocyte-Directed Inactivation of Connexin43

Abstract

Using a human glial fibrillary acidic protein (hGFAP) promoter-driven cre transgene, we have achieved efficient inactivation of a floxed connexin43 (Cx43) gene in astrocytes of adult mice. The loss of Cx43 expression was monitored in a cell-autonomous manner via conditional replacement of the Cx43-coding region by a lacZ reporter gene. In this way, we bypassed the early postnatal lethality previously reported for Cx43 null mice and characterized the phenotypic consequences of Cx43 deficiency in the CNS. Mice lacking Cx43 in astrocytes were viable and showed no evidence of either neurodegeneration or astrogliosis. Spreading depression (SD) is a pathophysiological phenomenon observed in the CNS that is characterized by a propagating wave of depolarization followed by neuronal inactivation. Inhibitors of gap junctional communication have previously been shown to block initiation and propagation of SD. In contrast, we observed an increase in the velocity of hippocampal SD in the stratum radiatum of mice lacking Cx43 in astrocytes. In the same brain subregion, dye-coupling experiments revealed a reduction in overall astrocytic intercellular communication by approximately 50%. This strongly suggests separate and different neuronal and glial contributions of gap junctional intercellular communication to SD. Concomitant with increased velocity of spreading depression, we observed enhanced locomotory activity in mice lacking Cx43 in astrocytes.

Connexin expression by radial glia-like cells is required for neurogenesis in the adult dentate gyrus

“…Indeed, in the neocortex of embryonic Cx43-deficient mice, changes in migration of neurons have been observed, which were however fully compensated during later development (34). The overall brain architecture of newborn (35) and adult mice lacking Cx43 in astrocytes was normal (36). The DG of adult constitutive dko mice also looked roughly normal, although our BLBP stainings revealed a clear reduction of RG-like cells in the SGZ, which might well account for the decreased proliferation.…”

The Complex of Ciliary Neurotrophic Factor-Ciliary Neurotrophic Factor Receptor α Up-Regulates Connexin43 and Intercellular Coupling in Astrocytes via the Janus Tyrosine Kinase/Signal Transducer and Activator of Transcription Pathway

“…The abolition of gap junctional communication has been shown to heighten neuronal vulnerability to various disturbances (Blanc et al, 1998;Naus et al, 2001;Ozog et al, 2002b). Furthermore, Cx expression, both dependent and independent of gap junctional communication, also has been shown to be protective against cellular injury (Siushansian et al, 2001;Lin et al, 2003;Nakase et al, 2003Nakase et al, , 2004Theis et al, 2003). These studies included the ubiquitous disruption of Cx43 expression as well as astrocyte-specific Cx43 knockout animal models.…”

“…These studies included the ubiquitous disruption of Cx43 expression as well as astrocyte-specific Cx43 knockout animal models. Specifically, Theis et al (2003) have identified that astrocytic-specific Cx43-deficient mice are characterized by increased spreading depression upon a CNS disturbance. Sohl et al (2000) have recognized that even a small decrease in astrocytic Cx43 can perturb proper spa- Plasmid pHXPL contained 6.7 kb of the murine Cx43 promoter inserted in front of a LacZ expression cassette.…”

Increased Apoptosis and Inflammation after Focal Brain Ischemia in Mice Lacking Connexin43 in Astrocytes

“…Therefore, cre-mediated recombination leading to loss of Cx43 expression could be monitored by X-Gal staining. 23 All mice were generated and genotyped 23 in the Institute of Genetics, University of Bonn, Germany.…”

“…In this study, we used mice with astrocyte-directed ablation of Cx43 23 to analyze the neuroprotective role of astrocytic gap junctions in focal brain ischemia. In Cx43(ϩ/Ϫ) mice, Cx43 is compromised not only in astrocytes but also in many other cell types and organs, including the heart and vasculature.…”