April 3, 2022

Impaired functional connectivity underlies Fragile-X syndrome

Fragile X syndrome (FXS), the most common form of inherited intellectual disability, is caused by a developmentally regulated silencing of the FMR1 gene, but its effect on human neuronal network development and function is not fully understood. Here we isolated isogenic human embryonic stem cell subclones one with a full FX mutation and one that is free of the mutation (control) but shares the same genetic background, differentiated them into induced neurons and compared the functional properties of the derived neuronal networks.
High-throughput image analysis demonstrates that FX neurons have significantly smaller cell bodies and reduced arborizations than control. FX neuronal networks are also able to generate spontaneous excitatory synaptic currents demonstrating that the neurons we generate in the lab are more mature than the previously used protocols. Microelectrode array (MEA) analysis demonstrated that FX networks are hyperexcitable with a significantly higher spontaneous burst firing activity compared to control. Most importantly, quantification of network connectivity demonstrated that the FX neuronal networks are significantly less synchronous than control, which can explain the origin of the development of intellectual dysfunction associated with the disease.

Lital Gildin1,2, Rossana Rauti3, Ofir Vardi3,4, Liron Kuznitsov-Yanovsky1,2; Ben M. Maoz3, 5, 6 Menahem Segal7, Dalit Ben-Yosef1,2,5,*

1Wolfe PGD Stem Cell Lab, Racine IVF Unit, Lis Maternity Hospital Tel-Aviv Sourasky Medical Center, Tel-Aviv, Israel. 2Department of Cell and Developmental Biology, Sackler Faculty of Medicine & 3Department of Biomedical Engineering & 4School of Electrical Engineering 5Sagol School of Neuroscience & 6The Center for Nanoscience and Nanotechnology, Tel-Aviv University, Israel. 7Department of Neurobiology, The Weizmann Institute, Rehovot, Israel.