2011-08-012024-05-14https://scholars.lib.ntu.edu.tw/handle/123456789/656710摘要：微核醣核酸為演化上具高度保留性之非轉譯型小核醣核酸分子，具有以轉譯後抑制方式控制大量標的基因表現之功能，涉及調控與演化、分化、細胞週期控制、生長/細胞凋之等重要細胞活動。常發現腫瘤細胞中微核醣核酸表現異於正常細胞，在不同腫瘤中微核醣核酸扮演抑癌或致癌角色。不同血液系細胞分化過程中亦可見特定微核醣核酸參與特定分化時序之調控。部份miRNAs異常表現與淋巴腫瘤有密切關聯。微核醣核酸-125b (miR-125b)是線蟲中負責調控蟲體演化時序的關鍵基因lin-4的同源性微核醣核酸。在許多腫瘤細胞的分析中常見miR-125b呈低度表現，但在具t(2;11)轉位或t(11;14)轉位之急性白血病與唐氏症相關之急性白血病中miR-125b表現增高。實驗中強迫血液幹細胞/前驅細胞表現過量miR-125b可使血液細胞增生，並使接受移植的小鼠發生各種血液腫瘤（急性T-, B-淋巴性白血病或骨髓系細胞增生疾病）。最近發現正常骨髓中血液幹細胞(HSC)的miR-125b表現遠高於其他已分化血液細胞，以病毒轉染增加HSC中miR-125b表現則會導致淋巴趨向性HSC增生並在受移植嵌合鼠中產生較多淋巴前趨細胞，暗示miR-125b有利HSC向淋巴系細胞分化。吾人欲研究與p190 Bcr-Abl(+) B-ALL相關之miRNA變化，已於共同主持人林淑華教授指導協助下成功產製miR-125b-1與miR-125b-2基因剔除小鼠。其二者表現型大不相同；miR-125b-2剔除鼠外觀健康，miR-125b-1基因剔除鼠則嚴重生長遲滯，並多在出生後數天內死亡；少數存活鼠則均呈現顯著胸腺、脾臟萎縮，且半數以上其胸腺T細胞與骨髓中Ｂ細胞有分化受阻情形。吾人欲以現有之miR-125b基因鼠為工具，研究miR-125b在造血／淋巴細胞生成中扮演角色，乃提出三年期研究計畫，目標為：（一）產製血液系統特異性miR-125b-1基因剔除小鼠，利用基因缺失系統（有別於先前研究使用之過量表現系統），探討miR-125b在造血/淋巴細胞生成中確實扮演的角色。（二）探索miR-125b對造血/淋巴細胞生成影響的分子機轉。（三）建構並測試miR-125b表現變化對p190 Bcr-Abl(+)白血病小鼠模型的影響，以探索miR-125b在p190 Bcr-Abl(+)急性白血病生成中之角色。<br> Abstract: MicroRNAs (miRNA) are phylogenetically conserved small non-coding RNAs known to post-transcriptionally regulate broad spectra of genes implicated in cell development, differentiation, cell cycle control and growth/apoptosis. Aberrant expression or miRNA has emerged to be a common feature of cancers. MiRNAs play as tumor suppressor or oncoMiR at different cellular context. Specific microRNAs are also shown to control important steps in hematopoiesis in different blood cell lineages. Abnormal expression of miRNAs in lymphoid malignancies is also well recognized to be functionally relevant to lymphomagenesis.MiR-125b is the mammalian ortholog of the C. elegans lin-4, a miRNA essential for normal temporal control of diverse developmental processes. Expression of miR-125b were generally repressed in human solid tumors but are found up-regulated in t(2;11) AML/MDS, t(11;14) B-ALL due to transactivation associated with genomic translocation of miR-125 locus, or trisomy 21-associated acute megaloblastic leukemia/transient leukemia. Enforced over-expression of miR-125b in hematopoietic stem/progenitor cells confers a proliferative advantage to hematopoietic cells and develops hematological malignancies (T-ALL, B-ALL, myeloproliferative disease) in recipient mice.Recently, miR-125b is found to preferentially express in the hematopoietic stem cells (HSC) than in differentiated blood cells. Over-expressing miR-125b induces expansion of lymphoid-biased HSC and increased early lymphoid progenitors in the spleen of chimeric mice. Due to our interest in studying the role of miR-125b in Bcr-Abl(+) B-ALL, we have successfully established mice genetic targeted for miR-125b-1 and miR-125b-2, with the great help from CoPI Dr. Lin Shu-Wha. While miR-125b-2 knockout mice did not show abnormal growth or lymphopoiesis, miR-125b-1 ablation results in growth restriction and postnatal premature death. The survival knockout mice showed marked thymic and splenic atrophy. A block in early T or B cell differentiation was found in a substantial portion of miR-125b-1 knockout mice. We propose to use the miR-125b gene-targeted mice to investigate the potential role of miR-125b in hematopoiesis/lymphopoiesis and in leukemia formation by a 3-year project, aiming at(1) Generating mice of conditional knockout in hematopoietic system, by breeding miR-125b-1fl/fl to vav-transgenic mice, to elucidate the role of miR-125b in the hematopoiesis and lymphopoiesis by a loss-of-function rather than the commonly used over-expression approach in previous studies.(2) Elucidating the molecular mechanisms by which miR-125b exert its influence on hematopoiesis/lymphopoiesis.(3) Construction of p190-Bcr-Abl B-ALL mouse model and test the change of disease progression corresponding to miR-125b level so that to investigate the role of miR-125b in leukemogenesis in the p190-Bcr-Abl B-ALL.