Differentiation of GABA(A) receptors in subcortical heterotopias: subunit distribution of displaced cortex reflects original commitment

Recent evidence suggests that the expression of GABAA receptor subunits is determined by an early innate program which can be further modified by thal amic input and local factors. We analyzed the GABAA subunit distribution in experimentally induced subcortical heterotopia which are a subgroup of neu ronal migration disorders. Heterotopias. consist of clusters of neurons whi ch have stopped migration early, before they have reached their final commi tment and well before thalamic afferents have reached their targets. Immuno histochemical analyses of five important GABAA receptor subunits revealed a n expression pattern typical for upper cortical layers reflecting the origi nal commitment of the heterotopic neurons. These results point towards deta iled innate determinants of cell fate which even contain information on rec eptor subunit distribution and are not affected by ectopic. positioning. (C ) 2001 Lippincott Williams & Wilkins.