title: SCF/KIT inhibition has a cumulative but reversible effect on the self-renewal of embryonic stem cells and on the survival of differentiating cells.
abstract: The receptor tyrosine kinase c-KIT is expressed in embryonic stem cells (ESCs) and adult stem cells, and many functional studies have demonstrated the importance of the SCF/KIT signaling pathway in adult stem cell maintenance. In this study, we show that a high level of KIT expression in wild-type ESCs correlates with an enhanced self-renewal and that inhibition of KIT signaling in ESCs for extended periods of time has a cumulative but reversible effect on self-renewal. Together these data suggest that continued KIT signaling in some cells within a self-renewing ESC population is required for optimal ESC function. Using a KIT blocking antibody, we recapitulated the phenotype we previously reported for genetically deficient KIT-null cells, demonstrating that SCF/KIT signaling is essential for the survival of differentiating ESCs. Here we show that this phenotype is also reversible. Pharmacological inhibition of JNK also had a cumulative but reversible detrimental effect on the survival of differentiating cells, thus recapitulating the Kit null phenotype and implicating JNK as a downstream mediator of KIT signaling. In contrast, the self-renewal of ESCs was unaffected by prolonged exposure to the JNK inhibitor, suggesting that JNK-independent downstream pathways are involved in KIT-mediated ESC self-renewal whereas KIT-mediated survival of differentiating ESC is likely to be JNK dependent.
authors.affiliation: MRC Centre for Regenerative Medicine, Edinburgh EH16 4UU, UK.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Fraser
authors.forename: A Helen
authors.initials: AH
authors.lastname: Taylor
authors.forename: Lesley M
authors.initials: LM
authors.lastname: Forrester
mesh_terms: D053687:Adult Stem Cells / Q000187:drug effects / Q000502:physiology; D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D053595:Embryonic Stem Cells / Q000187:drug effects* / Q000502:physiology; D055785:Gene Knockdown Techniques; D048031:JNK Mitogen-Activated Protein Kinases / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000235:genetics; D051379:Mice; D019009:Proto-Oncogene Proteins c-kit / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000276:immunology
chemical_list: D019138:Antibodies, Blocking; D019009:Proto-Oncogene Proteins c-kit; D048031:JNK Mitogen-Activated Protein Kinases