Glycine Promotes the Survival of a Subpopulation of Neural Stem Cells

Abstract

Glycine is mainly known as an inhibitory neurotransmitter in adult mature neurons, regulating neuronal network activity in the central nervous system. In contrast, during embryogenesis glycine can act as an excitatory neurotransmitter and generates the first electrical signal in immature neurons. The roles and functional significance of this excitatory glycinergic activity during neurodevelopment are still unclear. Using the zebrafish embryo as a model, we previously showed that glycine regulates proliferation and differentiation of neural stem cells (NSCs) to interneurons. Moreover, we identified that glycine signaling in NSCs is associated with several common developmental pathways and surprisingly also the p53-related apoptosis. Here we investigated how glycine signaling regulates NSC survival. First, we showed by two approaches, acridine orange staining and active caspase 3 immunostaining that defects in glycine signaling induce an early and transient cell death, which was suppressed by knockdown of p53. Then, we developed an NSC transplantation strategy to directly assess NSC-autonomous development upon perturbing glycine signaling. In vivo time-lapse imaging showed that disruption of glycine signaling disturbed the normal NSC interkinetic nuclear migration, leading to cell cycle arrest and apoptosis. Finally, we analyzed two main subpopulations of NSCs, expressing either nestin or GFAP, by in situ labeling and in transgenic lines expressing GFP in either population. We found that disruption of glycine signaling induced a drastic and selective loss of nestin-positive (nestin+) NSCs, which was only partially rescued upon p53 knockdown. Taken together, our findings support a role of glycine signaling in promoting survival of the nestin+ NSC subpopulation early during development.

Comparative in vitro study of the cytotoxicity of gelatine and alginate to human umbilical cord mesenchymal stem cells

“…Glycine signalling reduced cell apoptosis. 25 Arginine was consumed by human MSCs during cell culture to maintain cellular metabolis 26 , thereby implying that gelatine supports cell viability. Moreover, proliferation of MSCs was enhanced by arginine.…”

Glycine Regulates Neural Stem Cell Proliferation During Development via Lnx1-Dependent Notch Signaling

“…Zebrafish ( Danio rerio ) were maintained at 28°C under a 12-h light/dark cycle in the crCHUM Zebrafish Facility and they were raised and manipulated as per guidelines of the Canadian Council for Animal Care and protocol approved (N15018PDz) by the crCHUM ethics committee. To knockdown gene expression, embryos were microinjected with morpholino (MO) as described previously (Bekri and Drapeau, 2018).…”

“…Embryos were injected with Glr-MO or Ctrl-M, then subjected to in situ hybridization or immunostaining as described previously (Bekri and Drapeau, 2018).…”

“…Here we investigated the role of glycine signaling during neuronal development in the zebrafish embryo. We demonstrated previously that glycine signaling regulates NSC proliferation (Mcdearmid et al, 2006) and differentiation (Cote and Drapeau, 2012) by promoting survival of a subpopulation of NSCs (Bekri and Drapeau, 2018). An RNA sequencing analysis revealed that glycine signaling regulates several pathways in NSC development (Samarut et al, 2016) as well as some outlying genes, with Ligand of numb protein-x1 ( lnx1 ) among the most affected.…”

“…Lnx1 protein is a RING-type E3 ubiquitin ligase (De Bie and Ciechanover, 2011; Flynn et al, 2011) that degrades Numb (Dho et al, 1998), a cell fate determinant (Uemura et al, 1989). Furthermore, Numb is associated with Shh signaling (Di Marcotullio et al, 2011) and P53 signaling (Colaluca et al, 2008), both participating in glycine-dependent neurogenesis in zebrafish models (Samarut et al, 2016; Bekri and Drapeau, 2018). Importantly, Numb is well-known to be an inhibitor of Notch signaling (Roegiers and Jan, 2004; Mcgill et al, 2009), but further elucidations are required to understand how Notch and lnx1 activity correlates with other pathways to fine-tune neuronal development.…”