2012-08-012024-05-17https://scholars.lib.ntu.edu.tw/handle/123456789/686897摘要：脊髓肌肉萎縮症（Spinal Muscular Atrophy, 簡稱SMA）是一種遺傳性運動神經元疾病，目前臨床上尚未有治療的方法。SMA的疾病遺傳模式為體染色體隱性遺傳，其發病率約為6000至10,000分之一，而大多數SMA患者的兩股運動神經元存活基因(Survival motor neuron gene, 簡稱SMN1)皆發生了基因突變。SMA模式小鼠已由小鼠Smn基因剔除合併人類SMN2基因轉殖的方法所建立，而我們已於第三型SMA小鼠上詳細的分析了其表現型的特色，因此這個SMA模式小鼠對後續治療性試驗或SMA致病機制的相關研究可帶來極大的幫助。SMA脊髓運動神經元的退化為細胞凋亡的過程。Bcl-xL和Bax同屬於Bcl-2家族，但前者可抑制細胞凋亡，後者則可促進細胞凋亡。近來我們發現，帶有Bcl-xL轉殖基因的SMA小鼠及缺少Bax基因的SMA小鼠，其運動神經元的退化較輕，且生命較長。由於Bcl-2和SMN兩蛋白質彼此有交互作用，因此Bcl-xL和Bax亦可能和SMN有直接或間接的相互反應，並在SMA的發病機制中佔有重要的地位。是否Bcl-xL及Bax直接參與了SMA的致病機轉，或只是扮演了抑制或促進細胞凋亡的角色，需要進一步的研究。由於增進Bcl-xl或降低Bax的表現對SMA小鼠有所助益，因此，Bcl-xl/Bax此比例可作為一藥物篩檢的標的，亦即若有一藥物可明顯增加Bcl-xl及減少Bax的表現，則此藥物可能具有治療SMA的潛力。目前臨床上所使用的藥物，有些曾被證實在細胞或動物實驗中有增進Bcl-xl或抑制Bax的特性，因此，以這些具有抗細胞凋亡能力的藥物治療SMA小鼠來驗證其療效，將有機會成功尋找到合適的SMA治療藥物。本研究計畫的第一個目的為：了解Bcl-xL於SMA的致病機制中所扮演的角色。我們將嘗試驗證Bcl-xL和SMN蛋白質間是否有直接或間接的交互作用、Bcl-xL的表現是否影響SMN的典型功能、Bcl-xL是否可抵抗因SMN表現低下所引起的細胞凋亡反應及Bcl-xL基因轉殖對SMA小鼠脊髓內的mRNA和蛋白質表現所造成的變化。第二個目的為：了解Bax於SMA的致病機制中所扮演的角色。我們將嘗試驗證Bax和SMN蛋白質間是否有直接或間接的交互作用、Bax的表現是否影響SMN的典型功能、抑制Bax是否可抵抗因SMN表現低下所引起的細胞凋亡反應及Bax基因剔除對SMA小鼠脊髓內的mRNA和蛋白質表現所造成的變化。第三個目的為：尋找出一個可在SMA小鼠的脊髓內明顯增加Bcl-xl及減少Bax的抗細胞凋亡藥物，且其具有減緩SMA小鼠運動神經元退化及增進其運動功能的能力。<br> Abstract: Spinal muscular atrophy (SMA) is a hereditary progressive motor neuron diseasewithout available curative treatment currently. SMA exhibits an autosomal recessivepattern of inheritance with an incidence of 1 in 6000-10,000 newborns. Most SMApatients have homozygous gene mutation on the survival of motor neuron 1 gene (SMN1).The mice model of SMA has been generated by the mouse Smn knockout-human SMN2transgenic method. Following our detailed characterization of the phenotype for the typeIII SMA mice, this rodent model is suitable for use in testing therapies and investigatingdisease mechanisms for SMA.Degeneration of spinal motor neurons in SMA is mediated by apoptosis. Bcl-xL andBax, belonging to Bcl-2 family, are anti-apoptoic and proapoptotic factors, respectively.We previously showed that over-expression of Bcl-xL or knock-out of Bax in SMA micereduced motor neuron degeneration and prolonged life span. Since Bcl-2 interacts withSMN protein, Bcl-xL and Bax might also communicate with SMN directly or indirectlyand play an important role in SMA pathogenesis. Whether Bcl-xL or Bax involved in themajor disease pathway(s) of SMA or only plays a role in anti-apoptosis or proapoptosisneeds further investigation.Since up-regulation of Bcl-xL or down-regulation of Bax benefit SMA model mice,the ratio of Bcl-xL/Bax is another attractive target rather than SMN, where the potential toincrease Bcl-xL and decrease Bax expression may be of benefit to SMA patients. Manycurrent clinical available drugs revealed a capacity of Bcl-xL up-regulation and/or Baxdown-regulation in vivo or in vitro. Therefore, to screen these candidate drugs in SMAmice with a property of enhancing Bcl-xL and/or suppressing Bax might find out a gooddrug for future SMA clinical trials.The first aim of this project is to investigate the role of Bcl-xL on pathogenesis ofSMA. We will try to understand whether Bcl-xL directly or indirectly interacts with SMN,influences typical functional of SMN, and enhances anti-apoptotic effects in SMA-likeneuron cell lines. We will also screen the changes in transcripts and protein expression inspinal cord of SMA mice after providing Bcl-xL transgenes. The second aim of thisproject is to investigate the role of Bax on pathogenesis of SMA. We will try tounderstand whether Bax interacts with SMN, influences typical functional of SMN, andenhances proapoptotic effects. We will also screen the changes in transcripts and proteinexpression in SMA mice after Bax knock-out. In the third year, we intend to find out adrug, which can significantly increase the Bcl-xL and/or decrease the Bax levels in thespinal cord as well as attenuate the spinal motor neuron degeneration and preserve themotor function of SMA mice.細胞凋亡Bcl-xLBax脊髓肌肉萎縮症動物模式ApoptosisBcl-xLBaxspinal muscular atrophyanimal model