Store-Operated Calcium Entries Control Neural Stem Cell Self-Renewal in the Adult Brain Subventricular Zone

Abstract

The subventricular zone (SVZ) is the major stem cell niche in the brain of adult mammals. Within this region, neural stem cells (NSC) proliferate, self-renew and give birth to neurons and glial cells. Previous studies underlined enrichment in calcium signaling-related transcripts in adult NSC. Because of their ability to mobilize sustained calcium influxes in response to a wide range of extracellular factors, store-operated channels (SOC) appear to be, among calcium channels, relevant candidates to induce calcium signaling in NSC whose cellular activities are continuously adapted to physiological signals from the microenvironment. By Reverse Transcription Polymerase Chain Reaction (RT-PCR), Western blotting and immunocytochemistry experiments, we demonstrate that SVZ cells express molecular actors known to build up SOC, namely transient receptor potential canonical 1 (TRPC1) and Orai1, as well as their activator stromal interaction molecule 1 (STIM1). Calcium imaging reveals that SVZ cells display store-operated calcium entries. Pharmacological blockade of SOC with SKF-96365 or YM-58483 (also called BTP2) decreases proliferation, impairs self-renewal by shifting the type of SVZ stem cell division from symmetric proliferative to asymmetric, thereby reducing the stem cell population. Brain section immunostainings show that TRPC1, Orai1, and STIM1 are expressed in vivo, in SOX2-positive SVZ NSC. Injection of SKF-96365 in brain lateral ventricle diminishes SVZ cell proliferation and reduces the ability of SVZ cells to form neurospheres in vitro. The present study combining in vitro and in vivo approaches uncovers a major role for SOC in the control of SVZ NSC population and opens new fields of investigation for stem cell biology in health and disease. Stem Cells 2018;36:761-774.

Stable STIM1 Knockdown in Self-Renewing Human Neural Precursors Promotes Premature Neural Differentiation

“…Furthermore, morphological and immunohistochemical analyses identified a fate change in STIM1 knockdown NPCs where the balance between self-renewal and differentiation was altered significantly toward the latter. Mouse neural precursors with loss of function of the SOCE channel Orai exhibit very similar fate changes ( Prakriya et al, 2006 ; Lewis, 2007 ; Domenichini et al, 2018 ).…”

“…Interestingly, the attenuation of SOCE in mouse NPCs reduced their proliferation in vitro , as well as in the sub-ventricular zone (SVZ) of adult mouse brains in vivo ( Somasundaram et al, 2014 ). Moreover, a recent study demonstrated that pharmacological blockade of SOCE in mouse SVZ neural stem cells decreased proliferation and impaired self-renewal by shifting the type of SVZ stem cell division from symmetric proliferative to asymmetric ( Domenichini et al, 2018 ). Although mechanisms of neurogenesis are largely conserved among mammals, human neurogenesis shows some distinct attributes when compared to that of rodents, such as the presence of an astrocyte ribbon in the sub-ventricular zone (SVZ), higher turnover of hippocampal neurons and a rapid decline in the rate of neurogenesis with age ( Sanai et al, 2004 ; Knoth et al, 2010 ; Wang et al, 2011 ).…”

Calcium Channels in Adult Brain Neural Stem Cells and in Glioblastoma Stem Cells

“…In parallel, Ca 2+ imaging experiments unveiled the existence in NSCs, of intercellular Ca 2+ waves that are propagated through gap junctions and that are used by NSCs to communicate with each other and with neighboring niche astrocytes both under physiological conditions (Lacar et al, 2011) and pathological conditions (Kraft et al, 2017). Live cell Ca 2+ imaging has also allowed to observe spontaneous Ca 2+ oscillations in NSC/progenitors from the V-SVZ (Domenichini et al, 2018) as well as spontaneous high-frequency transients in migrating neuroblasts (Maslyukov et al, 2018). Along with the prominence of transcripts related to the Ca 2+ pathway in NSCs, these data lend support to the essential role of Ca 2+ in NSCs and their progeny.…”

“…In the V-SVZ, both Orai1 and TRPC1 have been detected along with STIM1 in NSCs and also in some neuroblasts (Skibinska-Kijek et al, 2009;Somasundaram et al, 2014;Domenichini et al, 2018). In these cells, SOCE could be triggered by various extracellular signals such as EGF that are used for cultures of NSCs (Reynolds et al, 1992;Somasundaram et al, 2014) or SDF1 that controls the tumor tropism of NSCs to glioblastoma (Zhao et al, 2008;Somasundaram et al, 2014).…”

“…In these cells, SOCE could be triggered by various extracellular signals such as EGF that are used for cultures of NSCs (Reynolds et al, 1992;Somasundaram et al, 2014) or SDF1 that controls the tumor tropism of NSCs to glioblastoma (Zhao et al, 2008;Somasundaram et al, 2014). The cholinergic agonist muscarine that stimulates NSC self-renewal could also elicit an intracellular Ca 2+ spike followed by a plateau phase that was dependent on SOCE (Domenichini et al, 2018). Conversely, SOCE was significantly but not totally reduced following the Orai1 knock-out (Somasundaram et al, 2014), indicating that Orai1 and other actors, possibly TRPC1, build-up functional SOCs in mouse NSCs.…”