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: Nuclei from day-75 cortical organoids (3 control libraries Ctrl 1-3 and 3 SMS libraries SMS 1-3, n=5 organoids per library) were isolated using the Miltenyi Nuclei Extraction Buffer (Miltenyi Biotec), following the manufacturer's guidelines with gentle MACS Dissociation and C tubes. Nuclei were prepared from samples for snRNA-seq analysis.