本實驗室於先前利用莫氏水迷津試驗篩選學習快與學習慢的大白鼠，取出其海馬迴組織並進行聚合酶連鎖反應差異顯示(PCR differential display)，結果顯示學習快與學習慢的大白鼠背側海馬迴之間共有98個cDNA片段有差異表現。把這些cDNA片段進行定序並利用BLAST資料庫比對，其中一個cDNA片段為大白鼠的pias1 [protein inhibitor of activated STAT1 (signal transducer and activator of transcription 1)] 基因。為了瞭解pias1基因的表現是否和空間學習有所關聯，隨機把大白鼠分成兩組，一組為有訓練組別(有空間線索與隱藏式平台)，另一組為無訓練的組別(沒有平台，作為游泳的控制組)同時進行莫氏水迷津學習試驗。試驗完畢，取出海馬迴組織進行即時定量聚合酶連鎖反應與西方墨點法來分析PIAS1的mRNA與蛋白質的表現。結果顯示有水迷津訓練的大白鼠，其PIAS1的mRNA與蛋白質表現皆明顯的高於無訓練的組別。為了更進一步確認PIAS1在空間學習中所扮演的角色，我們利用基因轉染的技術，轉染PIAS1 siRNA至大白鼠海馬迴CA1區域抑制PIAS1的表現。我們發現轉染PIAS1 siRNA至CA1區域會抑制大白鼠在水迷津的行為表現，然而轉染野生型的PIAS1質體基因至CA1區域卻會增進水迷津試驗的學習能力，同時我們也以西方墨點法發現，當轉染PIAS1 siRNA會增加STAT1 Tyr701的磷酸化，而轉染PIAS1 WT則會抑制STAT1 Tyr701的磷酸化。為了探討PIAS1促進記憶形成的分子機制，我們發現當轉染突變型的STAT1 Y701F質體基因至CA1區域，會抑制PIAS1 siRNA所造成記憶的損害。這些實驗結果代表著PIAS1會抑制STAT1 Tyr701的磷酸化，而PIAS1促進記憶的形成可能是藉由抑制STAT1 Tyr701的磷酸化而達成。另外，我們也單獨轉染突變型的STAT1 Y701F質體基因至CA1區域，水迷津實驗結果顯示會促進空間記憶的形成。目前PIAS1在免疫的角色已有許多研究證實，但是本篇研究是第一個提出PIAS1會參與哺乳類動物學習與記憶形成探討。 / Our laboratory has previously identified 98 cDNA fragments by using PCR differential display from rat dorsal hippocampus that are differentially expressed between fast learners and slow learners from the water maze learning task. After sequencing and BLAST analysis, one of these cDNA fragments encodes the rat pias1 [protein inhibitor of activated STAT1 (signal transducer and activator of transcription 1)] gene. In order to determine whether pias1 gene expression is associated with spatial learning, naïve rats were randomly assigned to the trained group (with visual cues and platform been present) and the non-trained group (without the platform as the swimming control). The dorsal hippocampus from these animals was dissected out at the end of the training and was subjected to RNA and protein extraction for real-time PCR and Western blot analysis of PIAS1 expression, respectively. Results revealed that the pias1 mRNA level and protein level was both higher in the hippocampus of trained rats than non-trained rats. To further examine the role of PIAS1 involved in spatial learning and memory, the specific PIAS1 siRNA was used to knockdown the expression of PIAS1 in rat hippocampal CA1 region. We found that transfection of PIAS1 siRNA to the CA1 area impaired water maze performance, whereas transfection of the wild-type PIAS1 DNA plasmid to the CA1 area facilitated water maze performance in rats. Meanwhile, PIAS1 siRNA increased STAT1 phosphorylation at Tyr701 whereas PIAS1 WT decreased STAT1 phosphorylation at this residue. In the examination of molecular mechanism underlying PIAS1-mediated memory facilitation, we have found that transfection of the STAT1 Y701F mutant plasmid antagonized the memory-impairing effect of PIAS1 siRNA, whereas transfection of STAT1 Y701F alone facilitated spatial memory formation. These results together suggest that one of the molecular mechanisms underlying PIAS1-mediated memory facilitation is through decreased STAT1 phosphorylation at Tyr701. All these manipulations did not affect visible platform learning in rats. In addition to the well documented role of PIAS1 in the immune system, here we have been the first to demonstrate a novel role of PIAS1 involved in spatial memory formation in rats.

STAT1是一個轉錄因子，在細胞生理功能中是非常重要的訊息傳遞者，在免疫系統具有抗病毒的角色，但是目前為止對於STAT1在中樞神經系統所扮演的角色仍不清楚。爲證實STAT1的表現與空間記憶的形成有關聯，我們將大白鼠分成兩組，一組為有訓練的組別，另一組則為無訓練的組別分別進行水迷津試驗，試驗完畢後取出大鼠的海馬迴CA1區域組織進行即時定量聚合酶連鎖反應與西方墨點法分析。結果顯示，經過水迷津訓練的刺激下，STAT1 mRNA與蛋白質分別減少約34 %及40 %，而STAT2 mRNA及蛋白質的表現則不受空間學習的影響。爲了進ㄧ步探討STAT1在空間學習記憶過程中所扮演的角色，實驗利用STAT1 siRNA轉染至海馬迴CA1區域抑制STAT1的表現，發現降低STAT1表現會促進大白鼠在水迷津試驗的學習能力，實驗同時也轉染STAT2 siRNA至CA1區域，結果顯示STAT2不參與大白鼠空間記憶的形成。本實驗室先前發現降低laminin β1表現量會促進大白鼠的空間學習記憶 (unpublished observation, 附錄二)，此外laminin β1基因啟動子上具有STAT1結合序列：interferon-γ activated site (GAS)。因此，實驗利用PC12細胞進行laminin β1報導基因分析，結果顯示STAT1會促進 laminin β1啟動子的轉錄活性。而爲了進一步探討在STAT1影響空間學習與記憶歷程中與laminin β1的關聯性，實驗利用STAT1 siRNA抑制大白鼠海馬迴CA1區STAT1的表現並促進空間學習與記憶的同時，發現laminin β1 mRNA及蛋白質表現量都受到STAT siRNA的抑制，而轉染野生型STAT1-Flag質體則會增加laminin β1 mRNA及蛋白質的表現量，顯示STAT1正向調控laminin β1的表現。本篇論文提出海馬迴CA1區域的STAT1參與動物空間學習與記憶的形成，其中可能與STAT1正向調控laminin β1的表現有關。 / STAT1 is a signal transducer and transcription factor in the cell. Several reports have indicated that STAT1 plays a critical role in immune response against virus infection in animals. However, the role of STAT1 in the central nervous system is still unclear. In the present study, we aimed to examine the role of STAT1 involved in spatial memory formation in rat and the possible downstream gene that STAT1 regulates. Rats were randomly divided into the trained group and the non-trained group. Animals were subjected to water maze learning according to the previous behavioral paradigm. Their hippocampus CA1 tissues were dissected out for STAT1 mRNA level and protein level determination. Results indicated that spatial training markedly decreased STAT1 mRNA level and protein level in the CA1 area, but this change was not found for STAT2 mRNA and protein expression. To further confirm the role of STAT1 involved in spatial learning and memory, animals were transfected with STAT1 siRNA in the CA1 area. Results showed that STAT1 siRNA transfection significantly facilitated water maze performance, whereas their water maze performance under STAT2 siRNA transfection was not altered. Previous studies from our laboratory have demonstrated that laminin β1 impairs spatial memory formation in rat (unpublished observation). In addition, promoter analysis indicates that the laminin β1 promoter region contains two GAS elements, which is the STAT1/STAT1 and STAT1/STAT3 binding site. Results from luciferase reporter assay revealed that transfection of STAT1 siRNA decreased laminin β1 promoter activity, whereas transfection of STAT1 wild-type plasmid increased laminin β1 promoter activity. To further study the relationship between STAT1 and laminin β1 in spatial memory formation, we used STAT1 siRNA to knockdown STAT1 expression and these animals were subjected to spatial training. We then determined their laminin β1 expression. Results showed that the laminin β1 mRNA level and protein level were both significantly decreased by STAT1 siRNA transfection. Besides, STAT1 wild-type plasmid transfection increased laminin β1 mRNA level and protein level in the CA1 area associated with spatial memory impairment. These results together suggest that STAT1 negatively regulates spatial memory formation. Further, STAT1 may impair spatial memory formation through increased laminin β1 expression.