Changes in the proliferative capacity of NG2 cell subpopulations during postnatal development of the mouse hippocampus.

Besides astrocytes and oligodendrocytes, NG2 proteoglycan-expressing cells (NG2 glia) represent a third subtype of macroglia in the brain. Originally described as oligodendrocyte precursor cells, they feature several characteristics not expected from mere progenitor cells, including synaptic connections with neurons. There is accumulating evidence that the properties of NG2 glia differ between different brain regions and developmental stages.

Astrocyte uncoupling as a cause of human temporal lobe epilepsy.

Glial cells are now recognized as active communication partners in the central nervous system, and this new perspective has rekindled the question of their role in pathology. In the present study we analysed functional properties of astrocytes in hippocampal specimens from patients with mesial temporal lobe epilepsy without (n = 44) and with sclerosis (n = 75) combining patch clamp recording, K(+) concentration analysis, electroencephalography/video-monitoring, and fate mapping analysis. We found that the hippocampus of patients with mesial temporal lobe epilepsy with sclerosis is completely devoid of bona fide astrocytes and gap junction coupling, whereas coupled astrocytes were abundantly present in non-sclerotic specimens.

Dysbalance of astrocyte calcium under hyperammonemic conditions.

Increased brain ammonium (NH4(+)/NH3) plays a central role in the manifestation of hepatic encephalopathy (HE), a complex syndrome associated with neurological and psychiatric alterations, which is primarily a disorder of astrocytes. Here, we analysed the influence of NH4(+)/NH3 on the calcium concentration of astrocytes in situ and studied the underlying mechanisms of NH4(+)/NH3-evoked calcium changes, employing fluorescence imaging with Fura-2 in acute tissue slices derived from different regions of the mouse brain. In the hippocampal stratum radiatum, perfusion with 5 mM NH4(+)/NH3 for 30 minutes caused a transient calcium increase in about 40% of astrocytes lasting about 10 minutes.

Characterization of Panglial Gap Junction Networks in the Thalamus, Neocortex, and Hippocampus Reveals a Unique Population of Glial Cells.

The thalamus plays important roles as a relay station for sensory information in the central nervous system (CNS). Although thalamic glial cells participate in this activity, little is known about their properties. In this study, we characterized the formation of coupled networks between astrocytes and oligodendrocytes in the murine ventrobasal thalamus and compared these properties with those in the hippocampus and cortex.

Germ-line recombination activity of the widely used hGFAP-Cre and nestin-Cre transgenes.

Herein we demonstrate with PCR, immunodetection and reporter gene approaches that the widely used human Glial Fibrillary Acidic Protein (hGFAP)-Cre transgene exhibits spontaneous germ-line recombination activity in leading to deletion in brain, heart and tail tissue with high frequency. The ectopic activity of hGFAP-Cre requires a rigorous control. We likewise observed that a second widely used nestin-Cre transgene shows germ-line deletion.

Dual reporter approaches for identification of Cre efficacy and astrocyte heterogeneity.

Gene inactivation reporters are powerful tools to circumvent limitations of the widely used Cre/loxP system of conditional mutagenesis. With new conditional transgenic mouse lines expressing the enhanced cyan fluorescent protein (ECFP) instead of connexin43 (Cx43) after Cre-mediated recombination, we demonstrate dual reporter approaches to simultaneously examine astrocyte subpopulations expressing different connexins, identify compensatory up-regulation within gene families, and quantify Cre-mediated deletion at the allelic level. Analysis of a newly generated Cx43 knock-in ECFP mouse revealed an unexpected heterogeneity of Cx43-expressing astrocytes across brain areas.

Role of astroglial connexin30 in hippocampal gap junction coupling.

The impact of connexin30 (Cx30) on interastrocytic gap junction coupling in the normal hippocampus is matter of debate; reporter gene analyses indicated a weak expression of Cx30 in the mouse hippocampus. In contrast, mice lacking connexin43 (Cx43) in astrocytes exhibited only 50% reduction in coupling. Complete uncoupling of hippocampal astrocytes in mice lacking both Cx30 and Cx43 suggested that Cx30 participates in interastrocytic gap junction coupling in the hippocampus.

Quality control of astrocyte-directed Cre transgenic mice: the benefits of a direct link between loss of gene expression and reporter activation.

Cre recombinase activity for cell-type restricted deletion of floxed target genes (i.e., flanked by Cre recognition loxP-sites) is often measured by separate matings with recombination-activated reporter gene mice.

Satellite glial cells in sensory ganglia: their possible contribution to inflammatory pain.

Neurons in dorsal root ganglia (DRG) are surrounded by an envelope of satellite glial cells (SGCs). Little is known about SGC physiology and their interactions with neurons. In this work, we investigated changes in mouse DRG neurons and SGC following the induction of inflammation in the hind paw by the injection of complete Freund's adjuvant (CFA).