Transcription factor induction of vascular blood stem cell niches in vivoPGE2 alters chromatin through H2A.Z-variant enhancer nucleosome modification to promote hematopoietic stem cell fateGlobal catalogue of microorganisms (gcm): a comprehensive database and information retrieval, analysis, and visualization system for microbial resourcesA chemical screen in zebrafish embryonic cells establishes that Akt activation is required for neural crest development