Investigation of the effects of GABA receptor agonists in the differentiation of human induced pluripotent stem cells into dopaminergic neurons

GABA system as the cause and effect in early development

GABA is the primary inhibitory neurotransmitter in the adult brain and through its actions on GABAARs, it protects against excitotoxicity and seizure activity, ensures temporal fidelity of neurotransmission, and regulates concerted rhythmic activity of neuronal populations. In the developing brain, the development of GABAergic neurons precedes that of glutamatergic neurons and the GABA system serves as a guide and framework for the development of other brain systems. Despite this early start, the maturation of the GABA system also continues well into the early postnatal period. In this review, we organize evidence around two scenarios based on the essential and protracted nature of GABA system development: 1) disruptions in the development of the GABA system can lead to large scale disruptions in other developmental processes (i.e., GABA as the cause), 2) protracted maturation of this system makes it vulnerable to the effects of developmental insults (i.e., GABA as the effect). While ample evidence supports the importance of GABA/GABAAR system in both scenarios, large gaps in existing knowledge prevent strong mechanistic conclusions.

Expression and Functional Properties of NMDA and GABAA Receptors during Differentiation of Human Induced Pluripotent Stem Cells into Ventral Mesencephalic Neurons

Ionotropic glutamate and GABA receptors regulate the differentiation and determine the functional properties of mature neurons. Both insufficient and excessive activity of these neurotransmission systems are associated with various nervous system diseases. Our knowledge regarding the expression profiles of these receptors and the mechanisms of their regulation during the differentiation of specialized human neuron subtypes is limited. Here the expression profiles of the NMDA and GABA_A receptor subunits were explored during in vitro differentiation of human induced pluripotent stem cells (iPSCs) into ventral mesencephalic neurons. The correlation between the neuronal maturation and the expression dynamics of these genes was investigated, and the functional activity of these receptors was assessed by calcium imaging. The role of NMDA and GABA_A receptors in neurite outgrowth and the development of spontaneous activity was analyzed using the viral transduction of neural progenitors with the reporter genes TagGFP and TagRFP. The data indicate that agonists of the investigated receptors can be employed for optimization of existing protocols for neural differentiation of iPSCs, in particular for acceleration of neuronal maturation.