Guoqing Guo1, Jifeng Zhang1, Li Xin1, Jing Chen1, Weizai Shen1, Lin Yuan2, Shizhen Zhong2

1Department of Anatomy, Medical College of Jinan University, Guangzhou  510630, Guangdong Province, China
2Institute of Clinical Anatomy, Southern Medical University, Guangdong Key Laboratory of Tissue Construction and Detection, Guangzhou  510150, Guangdong Province, China

the National Basic Research Program of China (973 Program), No. 2007CB512705*; the Natural Science Foundation of Guangdong Province, No. 8451063201000193*

Abstract
BACKGROUND: Rho GTPase family members have been shown to participate in neurite growth by regulating the neuronal cytoskeleton. However, there are very few reports of developmental roles of signaling molecules related to Rho GTPases.
OBJECTIVE: To investigate messenger ribonucleic acid mRNA expression of signaling molecules associated with Rho GTPases, including Rho-A, Rac-1, collapsin response mediator protein 1(CRMP-1), and tubulin β3 (Tub β3) during rat hippocampus development.
DESIGN, TIME AND SETTING: A non-randomized, controlled, animal experiment, based on differ-ent developmental stages of the rat hippocampus, was performed at the Guangdong Key Laboratory of Tissue Construction and Detection, Institute of Clinical Anatomy, Southern Medical University between December 2005 and July 2007.
MATERIALS: Trizol reagent was purchased from Invitrogen, USA. RNA PCR kit (AMV) Ver 3.0 and 150 bp DNA Ladder Marker were purchased from TaKaRa, Japan. Unless otherwise specified, all other reagents were purchased from Sigma-Aldrich, USA.
METHODS: Twenty-five Sprague Dawley rats were assigned to five groups (n = 5) according to developmental stages: embryonic (embryonic 15 days), neonatal (postnatal 5 days), juvenile (post-natal 1 month), adult (postnatal 3 months), and senile (postnatal 18 months).
MAIN OUTCOME MEASURES: Detection of mRNA expression of Rho-A, Rac-1, CRMP-1, and Tub β3 during various hippocampal developmental stages by reverse-transcription polymerase chain reaction.
RESULTS: Hippocampal mRNA expression of Rho-A, as well as Rac-1, reached peak levels at embryonic, juvenile, and senile stages, and was relatively less during neonatal and adult stages. mRNA expression of Rac-1 was greater than Rho-A during each hippocampal developmental stage. CRMP-1 mRNA expression levels were as follows: embryonic > neonatal > juvenile > adult < senile, while Tub β3 mRNA expression was embryonic > neonatal > juvenile > adult = senile.
CONCLUSION: Rho-A and Rac-1 shared similar expression profiles, which demonstrated similar variations during the entire rat hippocampus developmental process. However, Rac-1 mRNA ex-pression remained greater than Rho-A. Both CRMP-1 and Tub β3 mRNA expression profiles gradually declined during hippocampal development from embryonic to adult stages. Tub β3 mRNA expression arrested during the adult stage, and CRMP-1 mRNA expression increased during the senile stage.

Key Words: Rho GTPases; collapsin response mediator protein 1; tubulin; hippocampus; development; rat

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