| Abstract | Maternal infection during pregnancy is an environmental risk factor for the offspring to develop severe brain disorders, including schizophrenia and autism. However, only little is known about the neurodevelopmental mechanisms underlying the association between prenatal exposure to infection and the emergence of brain and behavioral dysfunctions in later life. Using a mouse model of prenatal immune challenge by the viral mimic polyriboinosinic-polyribocytidilic acid (PolyI:C), we explored the acute effects of maternal immune activation during pregnancy on the development of the fetal dopaminergic system, a neurotransmitter system known to be affected in schizophrenia and related disorders. We found that maternal immunological stimulation in early/middle pregnancy increased the number of mesencephalic dopamine neurons in the fetal brain at middle/late and late gestation. This effect was paralleled by changes in fetal expression of several genes known to be involved in dopamine neuron development, including the inductive signals sonic hedgehog (Shh) and fibroblast growth factor 8 (FGF8), as well as transcription factors Nurr1 and Pitx3. These findings provide initial in vivo evidence for a modulation of fetal dopaminergic development by maternal immune activation during pregnancy. Additional investigations of the neurodevelopmental effects of prenatal immune challenge are thus clearly warranted in order to further validate whether abnormal dopaminergic development may be a critical neuropathological mechanism underlying the precipitation of schizophrenia-like brain and behavioral dysfunctions emerging after in utero exposure to infection. |
| Abstract | GABAergic interneurons regulate cortical neural networks by providing inhibitory inputs, and their malfunction, resulting in failure to intricately regulate neural circuit balance, is implicated in brain diseases such as schizophrenia, Autism, and Epilepsy. During early development, GABAergic interneuron progenitors arise from the ventral telencephalic area such as medial ganglionic eminence (MGE) and caudal ganglionic eminence (CGE) by the actions of secreted signaling molecules from nearby organizers, and migrate to their target sites where they form local synaptic connections. In this study, using combinatorial and temporal modulation of developmentally relevant dorsoventral and rostrocaudal signaling pathways (SHH, Wnt, and FGF8), we efficiently generated MGE cells from multiple human pluripotent stem cells. Most importantly, modulation of FGF8/FGF19 signaling efficiently directed MGE versus CGE differentiation. Human MGE cells spontaneously differentiated into Lhx6-expressing GABAergic interneurons and showed migratory properties. These human MGE-derived neurons generated GABA, fired action potentials, and displayed robust GABAergic postsynaptic activity. Transplantation into rodent brains results in well-contained neural grafts enriched with GABAergic interneurons that migrate in the host and mature to express somatostatin or parvalbumin. Thus, we propose that signaling modulation recapitulating normal developmental patterns efficiently generate human GABAergic interneurons. This strategy represents a novel tool in regenerative medicine, developmental studies, disease modeling, bioassay, and drug screening. |