Novel fragile X syndrome 2D and 3D brain models based on human isogenic FMRP-KO iPSCs

Abstract

Fragile X syndrome (FXS) is a neurodevelopmental disorder, characterized by intellectual disability and sensory deficits, caused by epigenetic silencing of the FMR1 gene and subsequent loss of its protein product, fragile X mental retardation protein (FMRP). Delays in synaptic and neuronal development in the cortex have been reported in FXS mouse models, however, the main goal of translating lab research into pharmacological treatments in clinical trials has been so far largely unsuccessful, leaving FXS a still incurable disease. Here, we generated 2D and 3D in vitro human FXS model systems based on isogenic FMR1 knock-out mutant and wild-type human induced pluripotent stem cell (hiPSC) lines. Phenotypical and functional characterization of cortical neurons derived from FMRP-deficient hiPSCs display altered gene expression and impaired differentiation when compared with the healthy counterpart. FXS cortical cultures show increased proliferation of GFAP positive cells, likely astrocytes, increased spontaneous network activity and depolarizing GABAergic transmission. Cortical brain organoid models show increased proliferation of glial cells, and bigger organoid size. Our findings demonstrate that FMRP is required to correctly support neuronal and glial cell proliferation, and to set the correct excitation/inhibition ratio in human brain development.

Digital color-coded molecular barcoding reveals dysregulation of common FUS and FMRP targets in soma and neurites of ALS mutant motoneurons

“…Together, these data suggest that the FUS mutation might impact the synaptic component in axons and affect the function of genes in the soma involved in neuron development and morphogenesis. The same analysis in MNs derived from isogenic FMRP WT and FMRP KO human iPSCs [40] resulted in 42 differentially expressed targets in the soma and 18 in neurites (Fig. 3A, B).…”

“…Human iPSC lines used in this study are: FUS WT and FUS P525L (ref. [39]); FMR1 KO [40]; SYN1::HuD [21]; KOLF WT 2 and P525L16 (LL FUS-eGFP) [49]. Fig.…”