Local and CNS-Wide Astrocyte Intracellular Calcium Signaling AttenuationIn Vivowith CalEx^floxMice

Abstract

Astrocytes exist throughout the CNS and affect neural circuits and behavior through intracellular Ca 21 signaling. Studying the function(s) of astrocyte Ca 21 signaling has proven difficult because of the paucity of tools to achieve selective attenuation. Based on recent studies, we generated and used male and female knock-in mice for Cre-dependent expression of mCherrytagged hPMCA2w/b to attenuate astrocyte Ca 21 signaling in genetically defined cells in vivo (CalEx flox mice for Calcium Extrusion). We characterized CalEx flox mice following local AAV-Cre microinjections into the striatum and found reduced astrocyte Ca 21 signaling (;90%) accompanied with repetitive self-grooming behavior. We also crossed CalEx flox mice to astrocyte-specific Aldh1l1-Cre/ERT2 mice to achieve inducible global CNS-wide Ca 21 signaling attenuation. Within 6 d of induction in the bigenic mice, we observed significantly altered ambulation in the open field, disrupted motor coordination and gait, and premature lethality. Furthermore, with histologic, imaging, and transcriptomic analyses, we identified cellular and molecular alterations in the cerebellum following mCherry-tagged hPMCA2w/b expression. Our data show that expression of mCherry-tagged hPMCA2w/b with CalEx flox mice throughout the CNS resulted in substantial attenuation of astrocyte Ca 21 signaling and significant behavioral alterations in adult mice. We interpreted these findings candidly in relation to the ability of CalEx to attenuate astrocyte Ca 21 signaling, with regards to additional mechanistic interpretations of the data, and their relation to past studies that reduced astrocyte Ca 21 signaling throughout the CNS. The data and resources provide complementary ways to interrogate the function(s) of astrocytes in multiple experimental scenarios.

A perspective on astrocyte regulation of neural circuit function and animal behavior

“…In addition to astrocyte heterogeneity within a given organism's CNS, astrocytes show diversity across species (see Nagai, Yu et al, 2021 for a comparison between Caenorhabditis elegans, Drosophila melanogaster, Danio rerio, and Mus musculus). This raises the crucial yet experimentally challenging question of how astrocytes modulate neural circuit function and behavioral characteristics in humans.…”

Calcium signaling in astrocytes and gliotransmitter release

“…Even though there is a variety of tools to increase astrocyte Ca 2+ signaling, till recently, IP 3 R2 −/− mice and IP3 sponges (Agulhon et al, 2008;Petravicz et al, 2008) have been the only available options to achieve astrocyte Ca 2+ selective attenuation. Recent studies have provided new tools to lessen intracellular Ca 2+ release, such as activation of kappa-opioid receptor coupled to a Gi-GPCR selectively activated by salvinorin B (Vardy et al, 2015;Herrera Moro Chao et al, 2022) or by Cre-dependent expression of hPMCA2, a human plasma membrane Ca 2+ ATPase pump that constitutively extrudes Ca 2+ from astrocytes (Yu et al, 2018(Yu et al, , 2021. Decreases in astrocyte intracellular Ca 2+ levels have also been observed during neuropathology after astrocyte Gs-GPCR activation (Pham et al, 2021).…”

Astrocytic contributions to Huntington's disease pathophysiology

“…The former of these two possibilities is probably the most feasible. Subsequent studies have identified additional changes in astrocytic gene expression that accompany reduced Ca 2+ signaling, but their relation, if any, to HD pathophysiology is unknown and needs further work 97 . Furthermore, these studies do not rule out neuronal contributions to obsessive‐compulsive–like behaviors in parallel with astrocytic contributions.…”