胚胎幹細胞具有自我更新及可分化為來自三個胚層組織約200多種細胞的能力。因胚胎幹細胞經培養與體內或體外誘導分化為成體細胞後，呈現人類生物及生理上之組織細胞特性與功能，故其不但具有用於基礎醫學如胚胎發育與疾病細胞機制探討之意義，而且在臨床醫療如藥物篩選與移植醫療方面也具有應用之潛力。但是，因胚胎幹細胞在來源及應用方面受限於相關倫理等問題，近年來由此而發展出誘導多能性幹細胞。利用基因轉殖技術導入Oct3/4、Sox2、Klf4與c-Myc因子，而使細胞有效地倒程式化而重組誘導成為具有與胚胎幹細胞相似特性之誘導多能性幹細胞。已知細胞週期蛋白D1是調控細胞週期的重要因子之一，其於哺乳動物細胞內可與其它調控次單元組成全脢，並於癌症細胞內會過度表現而影響到轉錄、轉譯與蛋白質穩定性等因素。本研究探討細胞週期蛋白D1於幹細胞內及細胞倒程式化過程中所扮演的角色，從而進一步探討誘導多能性幹細胞在分子層面上與細胞週期蛋白D1的關聯性。我們的結果發現細胞週期蛋白D1不但於小鼠誘導多能性幹細胞中明顯被抑制，而且此抑制現象也發生於個別全能性相關因子轉殖後之小鼠纖維母細胞中。從我們實驗結果得知，細胞重組或重組之基因皆會抑制細胞週期蛋白D1的表現，此結果顯示細胞週期蛋白D1可能在細胞倒程式化或分化過程中扮演重要的角色。Embryonic stem cells (ESCs) have ability of self-renewal and differentiation to about 200 types of cells over from the three germ layers. Because somatic cells that appear the property of biological and physiological functions can be derived by ESCs through culturing and inducing for differentiation in vivo and in vitro, the study of ESCs has not only significance for the basic researches in embryo development and cell mechanism of pathology, but it has the potentiality for the biomedical application in drug screening and tissue transplantation. However, the clinical application of ESCs has been restricted by reasons of ethical issue and deriving cell source. Thus the techniques of induced pluripotent stem cells (iPSCs) have been developed recently. Basically, a cell reprogramming was occurred by transfection of Oct3/4, Sox2, Klf4 and c-Myc factors into the somatic cells. This reprogramming induces somatic cells effectively to iPSCs that cells exhibited pluripotency as well as ESCs. It has been known that Cyclin D1 is composed the regulatory subunit of a dimeric holoenzyme in mammalian cells. Cyclin D1 is frequently overexpressed in cancers and its overexpression also has been implicated to many factors including increased transcription, translation, and protein stability. In this study, we discuss what a role of cyclin-D1 is in the stem cells and the further correlation about cyclin-D1 with cell reprogramming in the molecular level. In our results, we found that cyclin-D1 was not only inhibited distinctly from the early stage of reprogramming in mouse ESCs, but also down-regulated by respectively tranfecting 4 defined pluripotent genes. Our data suggest that cyclin-D1 plays possibly an important role in cell differentiation and reprogramming.
