REGIONAL-ANALYSIS OF DEVELOPMENTAL-CHANGES IN THE EXTENT OF GLUR6 MESSENGER-RNA EDITING IN RAT-BRAIN

The extent of mRNA editing of the kainate receptor subunit GluR6 was e valuated in the cortex, hippocampus and cerebellum of embryonic brains at days 14 and 19 of gestation, in brains of animals aged 4, 25 days, or 3 months, and in hippocampal neurons isolated from embryonic brain s at day 19 of gestation and held in tissue culture for 2 or 8 days. T otal RNA was isolated and reverse transcribed into cDNA, which was use d as template for PCR across the edited base A in TMII of GluR6. The e xtent of editing was evaluated by restriction digest of PCR products w ith Bbv 1, gel electrophoresis and image analysis of bands. In all bra in structures studied the extent of editing was significantly upregula ted during development (P < 0.001). The most pronounced increase in th e extent of editing was observed between embryonic days 14 and 19. Hig hest levels were reached 4 days (94 +/- 1.3%) or 3 months after birth (95 +/- 1.7%) in the cortex and hippocampus, respectively. Notably, in hippocampal neurons held in tissue culture editing was sharply reduce d to 67 +/- 3.1% and 29 +/- 3.1% after 2 or 8 days in culture (P < 0.0 01 vs. the embryonic and adult state). The results illustrate that mod erate but significant regional differences exist in the regulation of GluR6 mRNA editing during development (cortex vs. hippocampus and cere bellum). Comparing developmental changes in the extent of editing of A MPA/kainate receptor subunits in vivo and in vitro may help to elucida te the molecular mechanisms of the editing process.