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Essence of stem cell found

01 November 2002
The Lancet Neurology, Volume 1, Number 7
Helen Pilcher

Researchers have identified the set of genes that make stem cells so special. Two teams led by Ihor Lemischka (Princeton University, NJ, USA) and Douglas Melton (Howard Hughes Medical Institute, MA, USA) have described a set of genes that are expressed in various mouse stem-cell types but are not expressed in mature, differentiated tissue. This molecular “essence of stem cell” helps throw light on the mechanisms that regulate stem-cell function, and will help researchers that hope to harness the therapeutic potential of stem cells.

Given that all stem cells share core functional properties, it is perhaps not surprising that they share a common genetic profile. “We wanted to know if there is such a thing as a generic stem cell molecular signature”, said Lemischka. “The question we have been asking is can we identify the molecular parts list, or toolbox, that the stem cell has at its disposal?”

Both groups used DNA microarrays to study gene expression, matching up active stem cell genes to thousands of mouse genes on a DNA microchip. The expression patterns from various types of stem cells were then compared with those from more committed cell types. In papers published on the same day (Science advanced online publication, Sept 12, 2002, DOI:10.1126/science.1073823 and DOI:10.1126/science.1072530 ), the two groups revealed a catalogue of over 200 genes that are common to embryonic, neural, and hematopoietic stem cells. The researchers believe that these genes code for characteristics that make stem cells stand out from the rest of the cellular crowd, allowing them to self-renew and give rise to more mature, differentiated cell types.

Until now, stem cells have been defined by their functionality and specific cell-surface markers. For the first time, this catalogue of stem cell genes provides a checklist for those attempting to characterise existing stem cells or discover new stem cells from different body regions. But while Melton's laboratory is currently using these results to help focus their hunt for pancreatic stem cells, Dafe Uwanogho (Institute of Psychiatry, UK) offered a word of caution. “Just because a gene is expressed by a stem cell it does not mean that is will be translated into a functional protein. To overcome this a functional proteomics approach could be used to determine the actual proteins expressed by stem cells compared with those expressed by non-stem cells.” Only then will the true “essence of stem cell” be revealed.

© Copyright 2002, The Lancet