Reversing Abnormal Neural Development by Inhibiting OLIG2 in Down Syndrome Human iPSC Brain Organoids and Neuronal Mouse Chimeras

Down syndrome (DS), caused by triplication of human chromosome 21 (HSA21), is the most common genetic origin of intellectual disability. Despite the limited success of current pharmacological interventions, little has been achieved to reverse the abnormal brain developmental in DS. Here, using human induced pluripotent stem cell (hiPSC)-based brain organoid and in vivo human neuronal chimeric mouse brain models, we demonstrate that the HSA21 genes OLIG1 and OLIG2 exhibit distinct temporal expression patterns during neuronal differentiation. The population of OLIG2-expressing ventral forebrain neural progenitors is overabundant in DS, which results in excessive production of calretinin- and somatostatin-expressing GABAergic interneurons and causes impaired recognition memory in DS chimeric mice. Furthermore, we find that overexpression of OLIG2 in DS alters the expression of GABAergic neuron lineage-determining transcription factors such as DLX1 and LHX8. We further show that OLIG2 can directly bind to promoter regions of DLX1 and LHX8 to increase their expression, leading to lineage specification of interneurons. Importantly, knockdown of OLIG2 largely reverses the abnormal global gene expression profile of early stage DS neural progenitors, reduces inhibitory neuronal population in DS organoids and chimeric mouse brains, as well as improves behavioral performance of DS chimeric mice. Therefore, OLIG2 potentially is a target for developing prenatal personalized therapeutics for intellectual disability in subjects with DS Overall design: Organoids (5-week old) generated from hiPSC lines derived from two DS patients (patient DS1 and DS3 and corresponding cell lines include DS1, control1, isogenic Tri-DS3 and Di-DS3, Tri-DS3+ContshRNA, and Tri-DS3+OLIG2shRNA hiPSCs) were used for RNA-sequencing. For each cell line, total 40-60 organoids collected from three batches of organoid cultures were pool together for RNA extraction and sample preparation. By pooling organoids, we increased the chances of identifying genes that were commonly up- or down-regulated in the three batches of cultures, whereas on the other hand, we decreased the chances of identifying genes that had varied expression levels in the three batches of cultures.

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Xu R, Brawner AT, Li S, Liu JJ, Kim H, Xue H, Pang ZP, Kim WY, Hart RP, Liu Y, Jiang P