Molecular and developmental deficits in Smith-Magenis syndrome human stem cell-derived cortical neural models
Smith-Magenis syndrome (SMS) is a genomic disorder caused by the deletion of a chromosomal region at 17p11.2. Individuals with SMS are frequently diagnosed with autism and have profound cortical deficits, including reduced cortex volume, mild ventriculomegaly, and epilepsy. Here, we developed human induced pluripotent stem cell (hiPSC)-derived neuronal models to understand how del(17)p11.2 affects cortical development. Hi-C identified local fusion and global reorganization of topological domains, as well as genome-wide miswiring of chromatin 3-dimensional (3D) interactions in SMS hiPSC and 3D cortical organoids. Single-nucleus RNA-seq of SMS cortical organoids identified neuropsychiatric disease-enriched transcriptional signatures and dysregulation of genes involved in catabolic and biosynthetic pathways, cell cycle processes, and neuronal signalling. SMS cortical organoids had reduced growth, enlarged ventricles, and impaired cell cycle progression. In a complementary hiPSC-derived 2D cortical neuronal model, we found SMS cortical neurons had accelerated dendritic growth, followed by neuronal hyperexcitability that was associated with a reduced potassium conductance. Our study demonstrates that del(17)p11.2 disrupts multiple steps of human cortical development, from chromatin wiring, transcriptional regulation, cell cycle progression, and morphological maturation to neurophysiological properties, and hiPSC-derived models recapitulate key neuroanatomical and neurophysiological features of SMS. Overall design: The study involved the derivation and maintenance of eight human induced pluripotent stem cell (hiPSC) lines—four from healthy individuals and four from Smith-Magenis syndrome (SMS) patients carrying the del(17)p11.2 deletion. hiPSCs were cultured under feeder-free conditions and validated for pluripotency and genomic integrity. Three-dimensional cortical organoids were generated from each of these lines using the AggreWell system and patterned with STEMdiff media. Organoids were cultured through staged differentiation protocols to promote cortical identity and maintained long-term in maturation media. The experimental design enabled comparative analyses of control and SMS cortical development models.