Expression profiling by high throughput sequencing
The discovery of significant heterogeneity in the self-renewal durability of adult haematopoietic stem cells (HSCs) has challenged our understanding of the molecules involved in population maintenance throughout life. Gene expression studies in bulk populations are difficult to interpret since multiple HSC subtypes are present and HSC purity is typically less than 50% of the input cell population. Numerous groups have therefore turned to studying gene expression profiles of single HSCs, but again these studies are limited by the purity of the input fraction and an inability to directly ascribe a molecular program to a durable self-renewing HSC. Here we combine single cell functional assays with flow cytometric index sorting and single cell gene expression assays to gain the first insight into the gene expression program of HSCs that possess durable self-renewal. This approach can be used in other stem cell systems and sets the stage for linking key molecules with defined cellular functions.