Abstract: The present invention relates to pluripotent stem cells and methods of promoting long term growth of such cells. In particular, the methods described are used to enhance the proliferation of hematopoietic stem cells, hematopoietic precursor cells, hemangioblasts and endothelial stem cells. The present invention also relates to methods of using such cells, comprising introducing such stem cells, into the host. The present invention also relates to pharmaceutical compositions comprising the cells and such compositions may include growth factors or cytokines to allow for further cell growth and/or cellular differentiation. The invention further relates to methods of in vivo administration of a protein or gene of interest comprising transfecting the stem cells grown by the methods described, with a construct comprising DNA which encodes a protein of interest and then introducing the stem cell into the host where the protein or gene of interest is expressed.

Abstract: A gene in humans and mice, designated C21, encodes a family of proteins that play a role in transcriptional regulation. Two isoforms (? and ?) produced by alternative splicing has been identified in humans. A transgenic model was created that shows that over-expression of C21 in mouse hematopoietic cells alters myeloid development and suggests that members of this family are involved in regulating stem cell differentiation. Over-expressing C21 in 3T3 fibroblasts increases their resistance to apoptotic stimuli. The C21 protein forms a complex with a class of molecules that plays a critical role in transcription, the co-repressors of nuclear hormone receptors.