Metabotropic glutamate receptor 5 responses dictate differentiation of neural progenitors to NMDA‐responsive cells in fragile X syndrome

Abstract

Disrupted metabotropic glutamate receptor 5 (mGluR5) signaling is implicated in many neuropsychiatric disorders, including autism spectrum disorder, found in fragile X syndrome (FXS). Here we report that intracellular calcium responses to the group I mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG) are augmented, and calcium-dependent mGluR5-mediated mechanisms alter the differentiation of neural progenitors in neurospheres derived from human induced pluripotent FXS stem cells and the brains of mouse model of FXS. Treatment with the mGluR5 antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP) prevents an abnormal clustering of DHPG-responsive cells that are responsive to activation of ionotropic receptors in mouse FXS neurospheres. MPEP also corrects morphological defects of differentiated cells and enhanced migration of neuron-like cells in mouse FXS neurospheres. Unlike in mouse neurospheres, MPEP increases the differentiation of DHPG-responsive radial glial cells as well as the subpopulation of cells responsive to both DHPG and activation of ionotropic receptors in human neurospheres. However, MPEP normalizes the FXS-specific increase in the differentiation of cells responsive only to N-methyl-d-aspartate (NMDA) present in human neurospheres. Exposure to MPEP prevents the accumulation of intermediate basal progenitors in embryonic FXS mouse brain suggesting that rescue effects of GluR5 antagonist are progenitor type-dependent and species-specific differences of basal progenitors may modify effects of MPEP on the cortical development. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 419-437, 2017.

Functional changes of AMPA responses in human induced pluripotent stem cell–derived neural progenitors in fragile X syndrome

“…Using Fura-2-based fluorescence recordings, we monitored [Ca 2+ ] i responses in all or most individual cells migrating out from the neurosphere ( Fig. 1B) (23,30). We observed that the proportion of glutamate-responsive cells was increased in FXS neurospheres when compared to controls at both time points studied (Fig.…”

“…In the neurosphere model, radial glia cells first appear from the differentiating neurospheres; differentiation of neuron-like cells closely follows radial glia during the first days of differentiation (30,49). We have previously shown that [Ca 2+ ] i responses through mGluR5 correlate with radial glia and functional AMPA/kainate (KA) receptor expression in many cells as soon as the first day of differentiation, whereas responses to N-methyl-d-aspartate (NMDA) are detectable in measurable amounts of cells after 7 days of differentiation (12,23,30,49). We sequentially exposed FXS and control neurospheres to (S)-3,5-dihydroxyphenylglycine (DHPG; a specific agonist of type I mGluR) and KA (an agonist of AMPA and KA receptors) at day 1 of differentiation and to KA and NMDA at day 7 of differentiation.…”

“…Previous studies have shown that human induced pluripotent stem cell (iPSC)-derived neural progenitors retain the FMR1 gene methylation (15) and differentially express a number of genes during neuronal differentiation compared with normal controls (20)(21)(22). Human FXS iPSC-derived neuronal cells and cortical progenitors derived from Fmr1-knockout (Fmr1-KO) mice show altered neurite growth (12,15,17,20,23), which reflects dysregulation of genes involved in neurite growth and axon guidance (20)(21)(22). There is evidence that abnormal calcium signaling through glutamate receptors contributes to the aberrant differentiation of FXS progenitors (23).…”

An Activating STAT3 Mutation Causes Neonatal Diabetes through Premature Induction of Pancreatic Differentiation

“…The patient-derived iPSC lines (STAT3 K392R cells) were then differentiated into pancreatic progenitors using a four-stage protocol based on previously published reports (Mfopou et al, 2010;Nostro et al, 2011;Toivonen et al, 2013b) with minor modifications to achieve efficient differentiation from all the cell lines ( Figure S2A; Supplemental Experimental Procedures). Healthydonor iPSC line HEL47.2 (Trokovic et al, 2015a), HEL24.3 (Trokovic et al, 2015b), HEL46.11 (Achuta et al, 2017), and human embryonic stem cell line H9 (Thomson et al, 1998) were used as controls.…”

SCN2A channelopathies in the autism spectrum of neuropsychiatric disorders: a role for pluripotent stem cells?

“…As Zhu et al suggest, the original monogenic models can then serve as a form of positive control against which more complex models can be compared. iPSC models have already been successfully used to identify cellular and molecular dysfunction that occurs in other forms of monogenic ASD-related disorders, including fragile X syndrome [21][22][23][24], Timothy syndrome [25][26][27][28], Rett syndrome [29][30][31][32], tuberous sclerosis [33][34][35][36], and neurofibromatosis type 1 [37][38][39][40]. As more monogenic models are added to the list, in vitro phenotypes can be compared and contrasted between the models to better understand the phenotypes from autism models with a more complex etiology.…”