FUNCTIONAL CHARACTERIZATION OF HUMAN IPSC NEURONS OF KLEEFSTRA SYNDROME ORIGIN

Kleefstra syndrome (KS) is a neurodevelopmental disorder associated with autism spectrum disorder (ASD), intellectual disability and hypotonia. The syndrome is caused by mutations in the EHMT1 gene, which plays a crucial role in gene expression. However, the impact of the functional loss of EHMT1 on the development of neuronal networks in humans remains unclear.
In this study, we modelled neuronal maturation and network formation of human iPSC-derived neurons from neurotypical (NT) and Kleefstra syndrome (KS) patients under in vitro conditions. To study the development of neural circuits, voltage-clamp, Ca²⁺ imaging, and multielectrode array (MEA) measurements were performed weekly for several weeks. KS-derived neurons showed spontaneous excitatory postsynaptic currents (sEPSCs) from week 1 of development, whereas in NT-derived cultures, these appeared only from week 3. Using Ca²⁺ imaging, KS cultures demonstrated elevated network activity as early as the first week; in contrast, the NT cultures reached a comparable level only by the fourth week. Multielectrode array (MEA) measurements also showed a significant rise in network activity in the KS arrays from the first week of induction. Notably, the activity in the KS cultures exhibited a decline towards the end of the observation period.
Our findings indicate that Kleefstra syndrome significantly influences network formation properties. This accelerated network activity may contribute to the abnormal neuronal network formation observed in Autism Spectrum Disorder.