ATRX is a chromatin-remodelling protein associated with neurodevelopmental disorders and gliomas, forming distinct nuclear foci associated with chromatin organization and phase-separated nuclear compartments. To visualize ATRX dynamics in live cells, we generated a human iPS cell (hiPSC) line with EGFP knocked in at the ATRX N-terminus using CRISPR/Cas12a-mediated genome editing. The modified hiPSCs retained pluripotency, normal karyotype, and trilineage differentiation potential. EGFP-ATRX localized to discrete nuclear foci, consistent with the phase-separated condensates described for ATRX, enabling real-time visualization of its chromatin association. This reporter line offers a valuable tool for studying ATRX function during differentiation and chromatin architecture development.

Mutations in the ATRX genes cause alpha-thalassemia X-linked intellectual disability (ATR-X) syndrome. Here, we show that ATRX influences the fate of human neural progenitor cells (hNPCs) by forming condensates through liquid-liquid phase separation (LLPS). The intrinsically disordered region (IDR) of ATRX is essential for LLPS and enables ATRX to form dynamic condensates that recruit co-activators. These condensates are necessary for ATRX localization at super-enhancers (SEs) in hNPCs, linking its compartmentalization to transcriptional regulation. Disruption of ATRX condensates alters gene expression and impairs neuronal differentiation. Our findings support a model in which ATRX phase separation regulates gene networks required for hNPC identity. These findings extend current understanding of ATRX function beyond its roles in chromatin structure and suggest that LLPS is a key regulatory mechanism by which ATRX supports neurodevelopment. This study opens avenues for further investigation into how dysregulation of ATRX and its phase-separation ability may contribute to the pathogenesis of ATR-X syndrome and related neurodevelopmental disorders.

Although neural stem/progenitor cells derived from human induced pluripotent stem cells (hiPSC-NS/PCs) are expected to be a cell source for cell-based therapy, tumorigenesis of hiPSC-NS/PCs is a potential problem for clinical applications. Therefore, to understand the mechanisms of tumorigenicity in NS/PCs, we clarified the cell populations of NS/PCs. We established single cell-derived NS/PC clones (scNS/PCs) from hiPSC-NS/PCs that generated undesired grafts. Additionally, we performed bioassays on scNS/PCs, which classified cell types within parental hiPSC-NS/PCs. Interestingly, we found unique subsets of scNS/PCs, which exhibited the transcriptome signature of mesenchymal lineages. Furthermore, these scNS/PCs expressed both neural (PSA-NCAM) and mesenchymal (CD73 and CD105) markers, and had an osteogenic differentiation capacity. Notably, eliminating CD73+ CD105+ cells from among parental hiPSC-NS/PCs ensured the quality of hiPSC-NS/PCs. Taken together, the existence of unexpected cell populations among NS/PCs may explain their tumorigenicity leading to potential safety issues of hiPSC-NS/PCs for future regenerative medicine.

A mutation in the chromatin remodeler chromodomain helicase DNA-binding 7 (CHD7) gene causes the multiple congenital anomaly CHARGE syndrome. The craniofacial anomalies observed in CHARGE syndrome are caused by dysfunctions of neural crest cells (NCCs), which originate from the neural tube. However, the mechanism by which CHD7 regulates the function of human NCCs (hNCCs) remains unclear. We aimed to characterize the cis-regulatory elements governed by CHD7 in hNCCs by analyzing genome-wide ChIP-Seq data and identifying hNCC-specific CHD7-binding profiles. We compared CHD7-binding regions among cell types, including human induced pluripotent stem cells and human neuroepithelial cells, to determine the comprehensive properties of CHD7-binding in hNCCs. Importantly, analysis of the hNCC-specific CHD7-bound region revealed transcription factor AP-2α as a potential co-factor facilitating the cell type-specific transcriptional program in hNCCs. CHD7 was strongly associated with active enhancer regions, permitting the expression of hNCC-specific genes to sustain the function of hNCCs. Our findings reveal the regulatory mechanisms of CHD7 in hNCCs, thus providing additional information regarding the transcriptional programs in hNCCs.