NLGN4X encodes neuroligin-4 X-linked, a postsynaptic cell adhesion molecule that plays a critical role in synapse formation and function through interactions with presynaptic neurexin family members 12. The protein regulates synaptic homeostasis and the balance between excitation and inhibition at synapses 1. NLGN4X function is modulated by phosphorylation at serine 712, which controls spine density and synaptic transmission, with phosphorylation by PKA reducing mature mushroom spines while unphosphorylated forms increase spine density and miniature excitatory postsynaptic current frequency 3. NLGN4X is strongly associated with autism spectrum disorders and intellectual disability, with multiple missense mutations identified in Chinese autism patients that are predicted to be damaging and absent in controls 1. A promoter mutation causing increased NLGN4X expression has been linked to autism and profound mental retardation 4. The gene forms an X-Y pair with NLGN4Y, sharing 97% homology, though NLGN4Y shows severe functional deficits and cannot compensate for ASD-associated NLGN4X mutations 5. NLGN4X also serves as a tumor-associated antigen overexpressed in gliomas, making it a potential target for immunotherapy 6.