The intrinsic specification of gamma-aminobutyric acid type A receptor alpha 6 subunit gene expression in cerebellar granule cells

The patterns of gamma-aminobutyric acid type A (GABA(A)) receptor subunit g ene expression in the brain are complex, For example, mouse hippocampal den tate granule cells express many subunit genes, whereas adult cerebellar gra nule cells, which may share differentiation mechanisms, have a smaller comp liment and uniquely express the alpha 6 subunit gene. To see how the alpha 6 expression component arises, i.e. if intrinsically or environmentally spe cified, we used a mouse line (Delta alpha 6lacZ) with a beta-galactosidase reporter inserted into the alpha 6 gene. Precursor cells from postnatal day 1 Delta alpha 6lacZ cerebellum were transplanted to the adult hippocampus and cerebellum of wild-type mice; 4 weeks after transplantation, Delta alph a 6lacZ cells expressed alpha 6-lacZ in the hippocampus, amygdala and cereb ellum. Thus, different adult environments support both the development and maintenance of alpha 6 gene expression from cerebellar granule cell precurs ors. Establishing alpha 6 gene expression is not likely to require specific patterns of neurotransmitter innervation or other factors present only in the developing brain; instead, alpha 6 expression can be timed and maintain ed autonomously.