CRE-mediated gene transcription in the peri-infarct area after focal cerebral ischemia in mice.

Cyclic AMP response element binding protein (CREB) is a transcription factor expressed constitutively primarily in neurons and is activated by phosphorylation at Ser(133) residue. CREB mediates expression of several neuroprotective proteins, including B-cell CLL/lymphoma 2 (BCL-2) and brain-derived neurotrophic factor (BDNF). Although phosphorylation of CREB after ischemia has been investigated extensively, CRE-mediated gene transcription after ischemia is not as well studied. We investigated temporal changes in CRE-mediated gene transcription in the cerebral cortex after focal ischemia in transgenic mice with a CRE-lacZ reporter gene. In the ischemic core, X-gal-positive cells, which reflected expression of the CRE-lacZ reporter gene, were observed rarely at any time point, though transient phosphorylation of CREB was detected. In contrast, the peri-infarct area showed a persistent increase in the number of X-gal-positive cells, of which more than half were positive for neuronal nuclei (NeuN). Our results suggest that CRE-mediated gene transcription, the pattern of which is not always consistent with that of CREB phosphorylation, occurs primarily in neurons in the peri-infarct area after focal cerebral ischemia and may be a neuroprotective response against ischemic insult.