DIFFERENTIAL REGULATION OF MYOCYTE ENHANCER FACTOR 2 (MEF2) CELL FATE DETERMINATION MOLECULES IN DENTATE GRANULE CELLS FOLLOWING PILOCARPINE-INDUCED STATUS EPILEPTICUS (SE)
Abstract number :
1.080
Submission category :
Year :
2003
Submission ID :
4005
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Robert C. Elliott, Fulvio A. Scorza, Brian Kruegel, Daniel H. Lowenstein Neurology, Beth Israel Deaconess Medical Center, Boston, MA; Clinical Neurology and Neurosurgery, Universidade Federal de S[atilde]o Paulo/Escola Paulista de Medicina, Sao Paulo, Bra
Previous studies in our laboratory have implicated the basic helix-loop-helix (bHLH) family of cell fate determination molecules as potentially involved in normal granule cell development as well as epilepsy-associated reorganization. bHLH members have been shown to cooperate with members of another family of cell fate determinants, the Myocyte Enhancer Factor 2 (MEF2) family of transcription factors, in directing the development of specific cell phenotypes in muscle myogenesis. The objective of this study is to investigate the possible involvement of the MEF2 family in aspects of neurogenesis and axon outgrowth associated with the onset of certain forms of epilepsy. To do so, we have analyzed the patterns of MEF2 family mRNA expression in the rat dentate gyrus following pilocarpine-induced status epilepticus (SE).
Adult, male Sprague-Dawley rats (180-200g) were given i.p. atropine methylbromide followed 20 min later by pilocarpine hydrochloride to induce SE. Seizure activity was monitored behaviorally and terminated with diazepam after 2h of convulsive SE. Control rats received saline instead of pilocarpine. Animals were killed 3, 7, 14, 28, or 60 days later, and perfusion-fixed brains were processed for non-radioactive in situ hybridization analysis of MEF2 family mRNAs. Digoxygenin-labeled in situ probes were transcribed from DNA templates generated by polymerase chain reaction (PCR) from neonatal or adult rat hippocampal cDNA libraries.
Using a pilocarpine-induced rat model of human temporal lobe epilepsy (hTLE), mRNA levels for each MEF2 family member (MEF2A, 2B, 2C, and 2D) were evaluated by in situ hybridization over a broad timecourse of epileptogenesis. Each MEF2 member was detected throughout the granule cell layer of normal, untreated adult rats. During epileptogenesis, MEF2C and 2D were markedly increased within 7-14 days following SE, and remained elevated above control levels for up to 60 days. In contrast, MEF2A and 2B demonstrated no apparent transcriptional regulation at any timepoint post-SE.
The differential regulation in the dentate gyrus of various members of the MEF2 family suggests a potential role for these molecules, particularly MEF2C and 2D, in epilepsy-associated reorganization of granule cell neurons. In addition, the coincident regulation of members of the MEF2 family, as shown here, and members of the bHLH family, as shown previously, may be indicative of a cooperative role of these two families of cell fate determination molecules in granule cell alteration following SE.
[Supported by: Funding support for this project has been provided by NIHRO1NS39950 (D.H.L.) and FAPESP (Brazil) (F.A.S).]