Chaotic, uncoordinated, and seemingly without rhyme or reason…no, it’s not the daily stampede towards the barista for your first coffee of the day; rather it’s the words used to describe the early stochastic phases of reprogramming differentiated cells into induced pluripotent stem cells. To bring a little order to the chaos, researchers from the laboratory of Marius Wernig have been working towards identifying cell surface proteins that select for those few cells which are very likely to become induced pluripotent stem cells in the future. Using these cell surface markers to select and analyse early induced pluripotent stem cells, the group have discovered new important transcriptional pathways at play in the early stages of cell reprogramming.
The researchers used mass cytometry; a strategy that uses antibodies tagged with rare earth elements to quickly and accurately identify specific cellular components allowing them to process a higher number of targets than normal flow cytometry. In this case, the researchers screened 176 antibodies, a colossal effort made easier with the implementation of this new strategy.
Using this high-throughput strategy they found:
- CD73, CD49d, and CD200 mark those cells which will successfully progress through the early stage and become induced pluripotent stem cells.
- The cell population identified is in a transient state between donor cell (fibroblast) silencing and pluripotency marker acquisition (induced pluripotent stem cells).
- These markers are all absent in both fibroblasts and induced pluripotent stem cells.
- Expression analysis of cells isolated with these markers highlights the importance of two transcriptional regulators in early reprogramming:
- Nr0b1 and Etv5 expression precede the expression of pluripotency associated factors
- Both factors are essential for the cell reprogramming process to occur.
This study represents an important step forward in the understanding of the chaotic early stages of cell reprogramming and could impact induced pluripotent stem cell production two-fold. First, through the generation of new reprogramming techniques utilising the newly identified transcription factors and second, the implementation of screens using the surface markers identified to select only for those few cells with the capacity to become iPSCs.
Assessment of human induced pluripotent stem cells awaits, but in the meantime read this mass-ive new study at Nature, April 2015