ARID1B encodes a component of SWI/SNF chr6 remodeling complexes that regulates transcription through ATP-dependent alteration of DNA-nucleosome topology 1. It is particularly important in neural development, where it functions in both neural progenitor-specific BAF (npBAF) and neuron-specific BAF (nBAF) complexes [UniProt]. During neurogenesis, ARID1B-containing npBAF complexes support neural stem cell self-renewal, while the transition to postmitotic neurons involves exchange of ARID1B-associated subunits for alternative components in nBAF complexes, which regulate genes essential for neuronal differentiation and dendrite growth. Pathogenic ARID1B variants cause developmental disorders spanning a clinical spectrum from nonsyndromic intellectual disability to Coffin-Siris syndrome 2. Loss-of-function mutations in ARID1B impair progenitor cell fate determination, particularly affecting the transition of neural progenitors to oligodendrocyte and interneuron precursor cells 3. ARID1B is identified as an autism spectrum disorder risk gene 4, with mutations causing asynchronous development of GABAergic and excitatory neuronal lineages 4. Disease-associated perturbations in ARID1B's intrinsically disordered regions disrupt chr6 localization and cBAF complex activity 1. These findings establish ARID1B as a critical regulator of human neurodevelopment, with its dysfunction contributing to intellectual disability and autism pathogenesis.