High induction threshold for transcription factor KROX-20 in the rat brain: partial co-expression with heat shock protein 70 following limbic seizures.
The transcription factor KROX-20, unlike many other immediate early genes, is not expressed in the rat hippocampus after bicuculline induced generalized seizures. Since limbic seizures are a more injurious stimulus, the KROX-20 expression profile was investigated in adult rats subjected to kainic acid induced limbic epilepsy at postictal intervals up to 48 h. Immunocytochemistry was performed using a specific polyclonal antiserum. In the hippocampus a sequential induction was observed with peak levels attained in dentate gyrus at 3 h, in CA1 at 8 h and in CA3 between 8 and 24 h, respectively. In contrast, no KROX-20 induction was found in hilus neurons. Prominent neuronal KROX-20 induction was also detected in other areas of the limbic system, in particular in amygdala and piriform cortex, as well as non-limbic regions such as neocortex and striatum. As is the case with KROX-20, heat shock protein (HSP) 70, a reliable marker for reversible neuronal injury, has a high induction threshold. Though not inducible in the hippocampus by generalized seizures, it is expressed after limbic epilepsy. Therefore, co-expression of KROX-20 and HSP70 was studied by a double labeling technique using a monoclonal antibody directed against the inducible form of HSP70. Neuronal subpopulations with perfect co-expression such as hippocampal CA1 neurons contrasted with others demonstrating partial co-induction (cortical neurons) or lack of co-expression (hilus cells), indicating that different stimuli trigger the activation of these two inducible genes.
Gass
P
P
Institute of Neuropathology, University of Heidelberg, FRG.
Herdegen
T
T
Bravo
R
R
Kiessling
M
M
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D051767:Early Growth Response Protein 2; D015870:Gene Expression; D006360:Heat-Shock Proteins / Q000096:biosynthesis*; D006624:Hippocampus / Q000378:metabolism; D007150:Immunohistochemistry; D007608:Kainic Acid / Q000633:toxicity; D008032:Limbic System / Q000503:physiopathology*; D008297:Male; D009474:Neurons / Q000378:metabolism*; D009928:Organ Specificity; D017966:Pyramidal Cells / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012640:Seizures / Q000139:chemically induced / Q000378:metabolism*; D014157:Transcription Factors / Q000096:biosynthesis*; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; D051767:Early Growth Response Protein 2; C497328:Egr2 protein, rat; D006360:Heat-Shock Proteins; D014157:Transcription Factors; D007608:Kainic Acid