Genetic abnormalities in synaptic proteins are common in individuals with autism; however, our understanding of the cellular and molecular mechanisms disrupted by these abnormalities is limited. SHANK3 is a postsynaptic scaffolding protein of excitatory synapses that has been found mutated or deleted in most patients with 22q13 deletion syndrome and about 2% of individuals with idiopathic autism and intellectual disability. Here, we generated CRISPR/Cas9-engineered human pluripotent stem cells (PSC) with complete hemizygous SHANK3 deletion ( SHANK3 +/− ), which is the most common genetic abnormality in patients, and investigated the synaptic and morphological properties of SHANK3-deficient PSC-derived cortical neurons engrafted in the mouse prefrontal cortex. We show that human PSC-derived neurons integrate into the mouse cortex by acquiring appropriate cortical layer identities and by receiving and sending anatomical projections from/to multiple different brain regions. We also demonstrate that SHANK3-deficient human neurons have reduced AMPA-, but not NMDA- or GABA-mediated synaptic transmission and exhibit impaired dendritic arbors and spines, as compared to isogenic control neurons co-engrafted in the same brain region. Together, this study reveals specific synaptic and morphological deficits caused by SHANK3 hemizygosity in human cortical neurons at different developmental stages under physiological conditions and validates the use of co-engrafted control and mutant human neurons as a new platform for studying connectivity deficits in genetic neurodevelopmental disorders associated with autism.

Glioblastoma multiforme (GBM) is one of the most aggressive and therapy-resistant brain tumors prevalent in both adults and children. Despite extensive research to understand GBM pathology, it remains unclear how neural cells in the human brain interact with GBM cells to support their brain propagation and therapy resistance and whether GBM cells exert any influence on the properties of human neural cells. In this study, we co-culture human stem cell-derived subpallial telencephalic organoids with patient-derived proneural or mesenchymal GBM spheroids to investigate their reciprocal interactions. We show that both proneural and mesenchymal GBM spheroids readily fuse and propagate with human organoids, forming organoid-GBM chimeras, without the need for exogenous growth factors. GBM cells within the chimeras adapt by modulating gene expression profiles consistent with diminished proliferation, heightened hypoxia, increased angiogenesis, and proneural-to-mesenchymal transition in proneural GBM. Both proneural or mesenchymal GBMs also exert an impact on the properties of neural cells in the chimeras, leading to the suppression of neuronal genes and an upregulation expression of genes associated with hypoxia and angiogenesis. Collectively, this study identifies specific genes and molecular pathways that can be altered in GBM and neural cells by reciprocal interactions in a human developing brain-like environment for an increased understanding of GBM pathology and future therapy development.