Difference between revisions of "Part:BBa K896969"

Latest revision as of 12:05, 27 April 2012

testican-1

Memory can be divided into two distinct forms: short-term memory long-term memory. Unlike short-term memory, long-term memory requires de novo mRNA and protein synthesis. The specific aim of this study is to analyze gene expression associated with contextual fear conditioning memory formation in the rat amygdala and examine the regional and subregional expression of the differentially expressed gene in the brain by in situ hybridization. Inhibitory avoidance learning was used as the behavioral model. Total amygdaloidal RNA isolated from good memory and control rats were subjected to PCR differential display analyses. One cDNA fragment corresponding to the testican-1 gene showed higher expression at 3 and 6 hours after inhibitory avoidance learning. Full length cDNA of the rat testican-1 was cloned and this 4452-bp cDNA sequence encodes a putative protein sequence containing 424 amino acids, which shows 95% and 97% homology to the human and the mouse testican-1, respectively. Differential expression of testican-1 gene was not confirmed by real-time RT PCR analyses. However, Northern hybridization demonstrated that testican-1 was mainly expressed in the brain and in situ hybridization showed subregional expression of the testican-1 gene in the brain. The distinct expression pattern of testican-1 gene in the brain was then compared with two recently cloned genes, testican-2 and testican-3. The testican-1 and testican-2 were expressed in the cytoplasm of different kinds of neuronal cells. The testican-1 gene has distinct subregional expression in the amygdala, notably in the lateral and basolateral nuclei, and medial portion of the central nuclei, nuclei that are involved in this learning model. Nevertheless, testican-2 and testican-3 have lower expression than testican-1 and no distinct subregional expression in the amygdala. Expression of these three genes was also examined in other brain areas. The mRNA level of testican-1 and testican-2 genes were highly expressed in CA3 and CA4, but rare in CA1 and CA2. In the granular layer of dentate gyrus, the mRNA levels of testican-2 and testican-3 can be detected but not that of the testican-1. In the cortex and insular cortex, both testican-1 and testican-2 were mainly expressed in the layer V. In the cerebellum, testican-1, -2 and -3 genes were strongly expressed in the Purkinje cell layers. The hybridization signals of testican-3 gene in these regions were too weak to be detected. The functional insight about testican-1 was discussed through its putative protein structure and expression pattern of the mRNA in various brain tissues. It is suggested that testican genes may have the abilities to regulate the neuronal morphology and synaptic plasticity in the brain.

Sequence and Features