Chang, X.; McKinley, M.; Li, W.; Yang, I.; Albizzati, E.; Iwasawa, E.; Guo, F.; Shillington, A.; Tchieu, J.

Excitation/inhibition (E:I) imbalance is a convergent mechanism in neurodevelopmental disorders (NDDs), yet whether NDD risk genes disrupt excitatory and inhibitory neurons through shared or distinct molecular programs remains poorly understood. Using human pluripotent stem cell-derived cortical projection and medial ganglionic eminence-like inhibitory neurons, we show that loss-of-function mutations in the chromatin reader ZMYND11 produce cell-type-selective vulnerability in cortical excitatory neurons. ZMYND11-deficient excitatory neurons exhibit hyperexcitability accompanied by de-repression of BMP signaling, dysregulation of glutamate receptor expression, and a shift toward non-brain splicing isoforms, whereas these molecular signatures are largely absent in ZMYND11-deficient inhibitory neurons. This cell-type selectivity is associated with differential upregulation of RBFOX family splicing regulators. Structure-function analysis reveals that MYND domain is required for normal progenitor dynamics and neuronal excitability. Together, these findings indicate that E:I imbalance in ZMYND11-associated NDD arises primarily from cell-type-selective vulnerability of excitatory cortical projection neurons and identify MYND domain as a critical determinant of neuronal function.