title: Spa-1 regulates the maintenance and differentiation of human embryonic stem cells.
abstract: Human embryonic stem cells (hESCs) are pluripotent, whereby they can proliferate endlessly and differentiate into many different cell types. At the molecular level, little is known of the mechanisms underlying their capability for self-renewal and differentiation. In the present study, we established two new hESC lines (AMC-hES1 and AMC-hES2) and demonstrated the existence of a regulator that may be a key molecule in hESC dynamics. Spa-1 is a principal Ras-proximate 1 (Rap1) GTPase-activating protein in hematopoietic progenitor cells that regulates Rap1-related signal transduction and is expressed restrictively in human adult tissues (bone marrow, thymus, and spleen). To investigate its functions in hESCs, we examined spa-1 expression profiles during hESC differentiation and used RNA interference (RNAi) to downregulate spa-1 in these cells. Our results show that Spa-1 is expressed in undifferentiated hESCs and is downregulated during hESC differentiation. In addition, the process of passing from the mode of self-renewal to that of differentiation in hESCs was regulated by spa-1 via Rap1/Raf/mitogen-activated protein kinase kinase/extracellular signal-related kinase signaling. An RNAi expression vector against spa-1 (pSUPER.retro.puro) was transfected into hESCs, which were seen to differentiate into three germ layers in spite of being in the undifferentiated condition. Based on our findings, therefore, it appears that spa-1 may be involved in hESC dynamics, and our results provide fundamental information regarding the self-renewal and differentiation of hESCs.
authors.affiliation: Department of Obstetrics and Gynecology, College of Medicine, University of Ulsan, Asan Medical Center, Songpa-gu, Seoul, Republic of Korea. yjleelee@amc.seoul.kr
authors.forename: Young-Jin
authors.initials: YJ
authors.lastname: Lee
authors.forename: Hee-Young
authors.initials: HY
authors.lastname: Nah
authors.forename: Seok-Ho
authors.initials: SH
authors.lastname: Hong
authors.forename: Ji-Won
authors.initials: JW
authors.lastname: Lee
authors.forename: Ilkyung
authors.initials: I
authors.lastname: Jeon
authors.forename: Jhang Ho
authors.initials: JH
authors.lastname: Pak
authors.forename: Joo-Ryung
authors.initials: JR
authors.lastname: Huh
authors.forename: Sung-Hoon
authors.initials: SH
authors.lastname: Kim
authors.forename: Hee-Dong
authors.initials: HD
authors.lastname: Chae
authors.forename: Byung-Moon
authors.initials: BM
authors.lastname: Kang
authors.forename: Chul Geun
authors.initials: CG
authors.lastname: Kim
authors.forename: Chung-Hoon
authors.initials: CH
authors.lastname: Kim
mesh_terms: D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D004622:Embryo, Mammalian / Q000166:cytology; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000378:metabolism / Q000502:physiology*; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D005822:Genetic Vectors; D006801:Humans; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D008954:Models, Biological; D009687:Nuclear Proteins; D034622:RNA Interference; D015398:Signal Transduction; D014162:Transfection
chemical_list: D020690:GTPase-Activating Proteins; D009687:Nuclear Proteins; C490403:SIPA1 protein, human; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases