Recently microarray technoloy has been implemented for measurements such as genome wide transcription patterns, and chromation immunoprecipitation analysis using genomic fragment arrays has been shown to be feasible for mammalian cells. Large scale gene knockdown experiments are also now achievable for analysis of gene function in cells from multizoates. Multipotential mesenchymal cells have been identified that can be propagated indefinitely amd differentiate within weeks into any one of a number of different cell lineages, in a manner controlled by the culture conditions. In addition to sequence specific DNA binding proteins, gene expression can be modified by the state of DNA methylation and the types and positions of modified residues in the core histones of nucleosomes. Further groups of proteins have been identified genetically and biochemically that function to stabilize gene activity or silence and interact with or participate in chromatin modification. The ability to rapidly undergo commitment to any of a number of cell lineages may be coupled to either limitations in the mechanisms for maintenance of gene activation or silencing or efficient functioning of mechanisms to reverse silenced and activated states of genes. Application of the new generation of genomic techniques could give fundamental insight into the mechanisms of multipotentiality and lineage choice and potential guide experimentation towards the development of regenerative medicine.
