ABSTRACT
The brain's serotonergic system centrally regulates several physiological processes and its dysfunction has been implicated in the pathophysiology of several neuropsychiatric disorders. While in the past our understanding of serotonergic neurotransmission has come mainly from mouse models, the development of pluripotent stem cell and induced fibroblast-to-neuron (iN) transdifferentiation technologies has revolutionized our ability to generate human neurons in vitro. Utilizing these techniques and a novel lentiviral reporter for serotonergic neurons, we identified and overexpressed key transcription factors to successfully generate human serotonergic neurons. We found that overexpressing the transcription factors NKX2.2, FEV, GATA2 and LMX1B in combination with ASCL1 and NGN2 directly and efficiently generated serotonergic neurons from human fibroblasts. Induced serotonergic neurons (iSNs) showed increased expression of specific serotonergic genes that are known to be expressed in raphe nuclei. iSNs displayed spontaneous action potentials, released serotonin in vitro and functionally responded to selective serotonin reuptake inhibitors (SSRIs). Here, we demonstrate the efficient generation of functional human serotonergic neurons from human fibroblasts as a novel tool for studying human serotonergic neurotransmission in health and disease.
Subject(s)
Cytological Techniques/methods , Fibroblasts/physiology , Serotonergic Neurons/physiology , Animals , Astrocytes/physiology , Basic Helix-Loop-Helix Transcription Factors/genetics , Basic Helix-Loop-Helix Transcription Factors/metabolism , Cell Line , Cell Transdifferentiation/physiology , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , GATA2 Transcription Factor/genetics , GATA2 Transcription Factor/metabolism , Genetic Vectors , Homeobox Protein Nkx-2.2 , Homeodomain Proteins/genetics , Homeodomain Proteins/metabolism , Human Embryonic Stem Cells/physiology , Humans , LIM-Homeodomain Proteins/genetics , LIM-Homeodomain Proteins/metabolism , Lentivirus/genetics , Mice , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/metabolism , Nuclear Proteins/genetics , Nuclear Proteins/metabolism , Transcription Factors/genetics , Transcription Factors/metabolism , Transcriptome , Zebrafish ProteinsABSTRACT
The evidence that new neuron addition takes place in the mammalian brain throughout adult life has dramatically altered our perspective of the potential for plasticity in the adult CNS. Although several recent reports suggest a latent neurogenic capacity in multiple brain regions, the two major neurogenic niches that retain the ability to generate substantial numbers of new neurons in adult life are the subventricular zone (SVZ) lining the lateral ventricles and the subgranular zone (SGZ) in the hippocampal formation. The discovery of adult neurogenesis has also unveiled a novel therapeutic target for the repair of damaged neuronal circuits. In this regard, understanding the endogenous mechanisms that regulate adult neurogenesis holds promise both for a deeper understanding of this form of structural plasticity, as well as the identification of pathways that can serve as therapeutic targets to manipulate adult neurogenesis. The purpose of the present review is to discuss the regulation of adult neurogenesis by neurotransmitters and to highlight the relevance of these endogenous regulators as targets to modulate adult neurogenesis in a clinical context.
