Golgi-dependent Reactivation and Regeneration of Quiescent Neural Stem Cells

Abstract

The ability of stem cells to switch between quiescent and proliferative states is crucial for maintaining tissue homeostasis and regeneration. In Drosophila, quiescent neural stem cells (qNSCs) extend a primary protrusion, which is removed prior to NSC reactivation. Here, we have unravelled that qNSC protrusions can be regenerated upon injury. This regeneration process relies on the Golgi apparatus which acts as the major acentrosomal microtubule-organizing centre in qNSCs. A Golgi-resident GTPase Arf1 and its guanine-nucleotide exchange factor Sec71 promote NSC reactivation and regeneration via the regulation of microtubule growth. Arf1 physically associates with its new effector Mini Spindles (Msps)/XMAP215, a microtubule polymerase. Finally, Arf1 functions upstream of Msps to target the cell-adhesion molecule E-cadherin to NSC-neuropil contact sites during NSC reactivation. Our findings have established Drosophila qNSCs as a new regeneration model and identified a novel Arf1/Sec71-Msps pathway in the regulation of microtubule growth and NSC reactivation.

Astrocytes control quiescent NSC reactivation via GPCR signaling-mediated F-actin remodeling

“…To understand whether this dynamics in the protrusion is important for F-actin polymerization in the soma of qNSCs, we examined F-actin dynamics labelled by GFP::utrophin-actin binding domain (GFP::utABD), followed by the severing of the protrusion using pico laser-induced ablation (see Methods for laser setting)( 17 ). As expected, GFP::utABD was not recovered at 10 mins post-injury (Fig.1I), as opposed to its rapid recovery in the fluorescence recovery after photobleaching (FRAP) experiment (Fig S1, A and B; 50% recovery at 100 seconds after photobleaching).…”

“…1K, 11:52; movie S4). While the protrusion in qNSCs persisted throughout the first cell division, it underwent a thinning process( 17, 37 ), possibly due to loss of F-actin patches during the reactivation.…”

“…The primary protrusion of quiescent NSCs is enriched with both microtubules and F-actin filaments( 11, 16, 17 ). Here, we unravel the structure of these F-actin filaments and characterize their function during quiescent NSC reactivation.…”

“…In the mammalian brain, astrocytic glia produce Insulin-like growth factor 1 (IGF-1) for the proliferation of NSCs( 9 ),( 10 ). In addition, intrinsic factors required for NSC reactivation have also been identified, such as spindle matrix proteins( 11 ), striatin-interacting phosphatase and kinase (STRIPAK) family proteins( 12 ), Hsp83( 13 ), CRL4 Mahj E3 ubiquitin ligase( 14 ), Pr-set7( 15 ), and microtubule-binding proteins Msps and Arf1( 16, 17 ). On the contrary, the activation of the evolutionarily-conserved Hippo pathway keeps NSCs in quiescence( 18, 19 ).…”

Patronin/CAMSAP promotes reactivation and regeneration of Drosophila quiescent neural stem cells

“…The microtubule minus-end binding protein Patronin is critical for NSC reactivation As microtubule regulators are involved in quiescent NSC reactivation (Deng et al, 2021;preprint: Gujar et al, 2022;Gujar et al, 2023), we investigated whether Patronin plays a role in NSC reactivation. At 24 h ALH, the vast majority of wild-type NSCs were reactivated and incorporated with EdU and only 11.5% of NSCs were quiescent and negative for EdU (Fig 1A -C).…”