MYOCYTE-SPECIFIC ENHANCER-BINDING FACTOR 2C EXPRESSION IN GERBIL BRAIN FOLLOWING GLOBAL CEREBRAL-ISCHEMIA

Myocyte-specific enhancer binding factor 2 (MEF2C) is a transcription factor expressed at high levels in brain. In this study, the distribut ion of MEF2C expression in brain was studied in normal adult gerbils a nd in adult gerbils subjected to 10 min of global cerebral ischemia. i n normal animals, MEF2C-immunoreactivity and messenger RNA expression were detected in cortex, hippocampus, caudate-putamen, thalamus, hypot halamus, and amygdala. Within the hippocampus, MEF2C-immunoreactivity and MEF2C messenger RNA were found in interneurons scattered through t he CA fields, a subset of which are parvalbumin-immunoreactive. MEF2C- immunoreactivity and MEF2C messenger RNA were also present in granule cells in the dentate gyrus. MEF2C-immunoreactivity was also detected i n microglia in the hippocampus. After transient forebrain ischemia, CA 1 pyramidal neurons, which are MEF2C-negative, degenerate whereas MEF2 C-positive interneurons survive. Our results thus indicate that MEF2C is a marker for hippocampal neurons that are resistant to ischemia. It remains to be determined whether MEF2C plays a direct role in protect ing the neurons that express it from ischemic injury. In addition, MEF 2C-immunoreactivity is present in microglia, and, after ischemia, ther e were increased numbers of MEF2C-immunoreactive microglia in CA1, so MEF2C-immunoreactivity is a marker of both resting and activated micro glia.