FOXG1 (forkhead box G1) is a transcription repressor that plays a critical role in establishing regional brain subdivisions and telencephalic development 1. As a sequence-specific DNA-binding transcription factor, FOXG1 regulates gene expression through RNA polymerase II-dependent mechanisms and chr14 remodeling in the nucleus. FOXG1 demonstrates pleiotropic effects on cell fate specification, with particular importance in Layer 6 corticothalamic neuron development and the regulation of GABAergic versus glutamatergic neuron differentiation 23. Dysregulation of FOXG1 expression has been implicated in neurodevelopmental disorders. Pathogenic variants in FOXG1 are associated with developmental epileptic encephalopathy, with all identified mutations being de novo 4. FOXG1 mutations cause Rett syndrome congenital variant and contribute to autism spectrum disorder phenotypes, where FOXG1 overexpression drives overproduction of GABAergic neurons and correlates with symptom severity 3. Additionally, FOXG1-related disorders present with hyperkinetic movement abnormalities including chorea and stereotypies in early childhood 56. These findings establish FOXG1 as essential for normal cortical development and suggest that precise dosage regulation is critical for proper neurodevelopmental outcomes.