Expression of Msi2 within the hematopoietic system. (A) Diagram of the genetic modification of the Msi2 locus in Msi2^Gt/Gt mice. A promoterless reporter gene (βgeo) was inserted into the mouse genome by integration of a retroviral gene-trap vector (rFlipROSAβgeo +1) carrying a splice acceptor sequence (SA) and a polyadenylation signal (pA). It was inserted in intron 5, at 99 465 bp 3′ of exon 5 of Msi2, generating an Msi2/βgeo fusion protein, preserving the N-terminal part of Msi2. (B-E) Expression of Msi2 using staining for β-galactosidase activity with a fluorescent substrate (FDG) as the readout. (B) Expression of Msi2 in LSK cells (Lin⁻c-Kit⁺Sca-1⁺) as well as in Lin⁻ and Lin⁺ BM subsets of an Msi2^+/Gt adult mouse. FDG fluorescence intensity is shown for cells incubated with the reagent (solid lines) or kept untreated (broken lines). (C) Histograms showing the percentage of cells expressing Msi2 in LSK cells, intermediate progenitors, and mature cells. Error bars indicate SEM (n = 5). (D-E) Expression of Msi2 in LT-HSCs, ST-HSCs, and LMPPs (n = 5).