A Developmental Study On The Expression Of Noggin And BMP4 In The CNS Of Rats And Their Association With Learning And Memory

As an important embryonic developmental protein, the mammalian noggin is similar in its sequence to Xenopus. In humans, the noggin gene has been localized to chromosome 17q22, and in the mouse, it is localized to a region of chromosome 11. Noggin cDNA contains a single reading frame encoding a 26 kD protein, which has been identified to effect neural induction through antagonizing bone morphogenetic protein-4 (BMP4). Valenzuela has demonstrated that mammalian noggin and its expression in the adult nervous system. In addition, chordin as another antagonist of BMP4, has been demonstrated its spread expression during postgastrulation embryogenesis and in postnatal brain, indicating an important neural inducer keep working in the adult nervous system .Up to now, no reports regard noggin and BMP4 genes expression and their functions.In this project, the expression of noggin and BMP4 in central nervous system (CNS) of rats during development and excitotoxic brain injury was detected using in situ hybridization histochemistray (ISHH) and reverse transcription-polymerase chain reaction (RT-PCR). By using antisense technique combined with bromodeoxyuridine (BrdU)-labeling and immunocytochemistry(ICC) methods ,the effect of noggin on hippocampus neurogenesis in adult rats was explored. Combining with Morris water maze (WMW) and the recording of long term potentiation (LTP) , the expression of noggin and BMP4 and its relation to learning and memory in adult hippocampus were investigated. The main results were as follows:1. The expression of noggin mRNA in the CNS of rats during development was detected with ISHH.It was revealed that densely and deeply stained noggin mRNA positive cells were detected in cortex, hippocampus, cerebellum, and nucleus of hypothalamus and thalamus in embryonic day (E)16 rats. The number of noggin mRNA positive cells was increased in the thalamus and medulla oblongata at postnatal day (P)1-2 , whereas decreased in the hippocampus and cortex. The number of noggin mRNA positive cells was decreased significantly in brain at 1 week postnatal(P1W) , and began to increase at P2W , especially in the cortex and hippocamps. Strong positive signal can be detected in the frontal cortex , parietal cortex ,cingulated cortex, hippocampus , olfactory and cerebellum at 1 month postnatal (P1M). The expression of noggin mRNA began to decline at P3M , only sparse noggin mRNA positive cells can be seen in CNS at P18M. Furthermore, there is no noggin mRNA positive cells seen in the spinal cord of rats during development. This indicated that noggin could play an important role in CNS development of rats .2. The expression of BMP4 mRNA in the CNS of rats was detected with ISHH.It was showed that BMP4 mRNA positive cells were majored in cerebellum and olfactory at El6. Strong positive signal was seen in hypoglossal nucleus, and moderate signal also seen in spinocerebellar tract, and spinal lemniscus at P1-2 . The number of BMP4 mRNA positive cells was increased in the frontal cortex, parietal cortex, and hippocampus subiculum at P1W. The peak of BMP4 expression in cortex and hippocampus of rats was at P1M, strong positive signal was observed in temporal cortex and periamydaloid cortex. Widely distributed BMP4 mRNA positive cells were detected in CNS at P3M , strong positive signal was observed in hippocampus, temporal cortex and periamydaloid cortex, lateral nucleus of thalamus andparaventricular nuleus of hypothalamus. BMP4 mRNA positive cells were also found in cortex, hippocampus,hypothalamus and thalamus at P18M .3. The level of noggin mRNA and BMP4 mRNA was analysed in frontal cortex and hippocampus of rats at different developmental stage using a semi-quantitative RT-PCR assay.It was revealed that the level of noggin mRNA in frontal cortex was decreased significantly in P1W rats , high level of BMP4 mRNA was detected in P1M and P3M rats. The expression of noggin mRNA and BMP4 mRNA in hippocampus showed opposite expression pattern. The peak of expressio...