Understanding how adult stem cells generate neurons is critical for advancing regenerative medicine, yet few in vivo models allow for the direct study of adult stem cell fate specification. The planarian Schmidtea mediterranea offers a powerful system to investigate these mechanisms, owing to its abundant adult pluripotent stem cells, termed neoblasts, and its capacity to regenerate a molecularly complex nervous system. The SoxB1 family of transcription factors is broadly implicated in ectodermal lineage commitment, and in planarians, the SoxB1 homolog soxB1-2 has been shown to promote neural and epidermal differentiation. However, the mechanisms by which soxB1-2 influences chromatin dynamics and transcriptional programs during adult neurogenesis remain unknown. To address this, we combined ATAC-seq and RNA-seq to assess how soxB1-2 RNAi knockdown alters chromatin accessibility and gene expression. Disrupting soxB1-2 resulted in reduced chromatin accessibility and transcriptional downregulation at neural and epidermal loci, consistent with a pioneer-like role in chromatin priming. We identified 31 candidate downstream targets exhibiting concordant changes in chromatin accessibility and gene expression. Among these, we identified and characterized mecom, a transcription factor potentially involved in regulating mechanosensory signaling genes, along with castor and cux1, which may regulate genes associated with sensory neurons and CNS development and function. Spatially enriched head tissue sampling enabled the detection of soxB1-2-responsive genes within rare neural subtypes that were missed in previous whole-worm assays. These findings offer mechanistic insight into adult ectodermal lineage specification and establish a framework for understanding chromatin-mediated neurogenesis in regenerative systems
