Practice question

L1 cell adhesion molecule mediates calcium-independent homophilic binding through immunoglobulin domains promoting cell-cell adhesion critical for neural crest migration and axon guidance. Ethanol at concentrations achieved after binge drinking interacts with extracellular domain at Gly-122 pocket, converting L1 to non-adhesive conformation, blocking homophilic binding and downstream Erk signaling required for growth cone motility. Other adhesion molecules like N-CAM or integrins are resistant at those doses, showing selectivity. Impaired L1 function replicates migration deficits seen in L1 mutation disorders such as hydrocephalus and contributes to fetal alcohol facial and brain anomalies resulting from defective cell adhesion.