Neural crest induction requires SALL4-mediated BAF recruitment to lineage specific enhancers
Neural crest induction begins early during neural plate formation, requiring precise transcriptional control to activate lineage-specific enhancers. Here, we demonstrate that SALL4, a transcription factor associated with syndromes featuring craniofacial anomalies, plays a critical role in early cranial neural crest (CNCC) specification. Using SALL4-het-KO human iPSCs to model clinical haploinsufficiency, we show that SALL4 directly recruits BAF to CNCC-lineage specific enhancers at the neuroectodermal stage, specifically when neural crest gene expression is induced at the neural plate border. Without functional SALL4, BAF is not loaded at chromatin, leaving CNCC enhancers inaccessible. Consequently, the cells cannot undergo proper CNCC induction and specification due to persistent enhancer repression, despite normal neuroectodermal and neural plate progression. Moreover, by performing SALL4 isoform-specific depletion, we demonstrate that the SALL4A is the isoform essential for CNCC induction and specification, and that SALL4B cannot compensate for SALL4A loss in this developmental process. In summary, our findings reveal SALL4 as essential regulator of BAF-dependent enhancer activation during early stages of neural crest development, providing molecular insights into SALL4-associated craniofacial anomalies.