(Right) AchE staining (red arrow). [6]. Antibodies and reagents All antibodies were purchased from BD pharmingen except for CD42b, (PE-conjugated GpIb, a kind gift from B. Nieswandt (Germany). Valproic acid was from Sigma. Cellular staining, ploidy, FACS analyses, real-time PCR, MkP purification, nucleofection and Cre-mediated excision in MKD1 were as described [7]. GpVI promoter A 330 bp sequence encompassing the promoter (?330/+1) was PCR-amplified from mouse genomic DNA and cloned into pGL4b (Promega). Luciferase-based transactivation assays were performed in 3T3 and MKD1 cells as described [7], [8]. For Chip, primers and 5FAM-3TAMRA labelled probes were selected from unique sequences in Rosiridin the locus and appropriate external controls using Primer Express Software (sequences available upon request). Input and immunoprecipitated material were analysed in duplicates relative to a sequence in the locus. Differentiation Cells were seeded at a density of 2C4105 cells/ml in presence of Epo, IL-3 and valproic acid for 3 to 7 days. Results Rosiridin and Discussion In an attempt to study the functional role of SCL/Tal1, a grasp regulator of hematopoiesis (see [7] and references therein), in ES cell-derived megakaryopoiesis, we generated ES cells. Importantly, using differentiation assays, we did not observe morphological or biological differences between wild-type and ES cell-derived hematopoietic LRIG2 antibody cells and, more specifically MKs (data not Rosiridin shown), thereby establishing the neutrality of the loxP sites introduced into the locus. Hematopoietic cell lines were then established from ES cells (Physique 1A). Briefly, Hox-11 transduced ES cells were differentiated into embryoid bodies (EBs). Day 7 EBs were dissociated and cells maintained in liquid cultures in three different cytokine conditions (Epo/IL3, Tpo/KL, and Epo/KL). After 6 and 8 weeks, hematopoietic cells were seeded onto methylcellulose. Immortalized colonies were isolated 8 to 10 days later and expanded in liquid culture in the appropriate cytokine condition. Morphological inspection and immuno-phenotyping identified megakaryocytic (MK) cell lines in the Epo/IL3 condition only (not shown). In agreement with this, most Hox11-immortalized hematopoietic clones are IL3-dependent for their growth and survival [5]. Several immortalised MK clones showing different degrees of differentiation were obtained, as judged by cellular staining (MGG and Acetylcholine Esterase, AchE, a MK-specific marker) (Physique 1B) and by the percentage of cells that (i) express CD41+ (GpIIb) and CD42b+ (GpIb) (two cell surface markers expressed in differentiating MKs); (ii) are positive for AchE; (iii) exhibit ploidies greater than 8N (Table 1). Whilst clones C7, E7 and G10 showed relatively high levels of CD41 and CD42b expression (ranging from 67% to 96% Rosiridin and 12% to 30%, respectively) and AchE positivity (15% to 90%), clone D1 (MKD1) showed lower CD41, CD42b and AchE expression (40%, 2.8% and 2% respectively). Although clones E7 and G10 seemed more advanced Rosiridin in their differentiation than the MKD1 clone, their ploidy (4% of E7 and G10 cells had a ploidy greater than 8N, compared to 3% for the MKD1 clone) and their gene expression profile, when assayed for the MK-specific markers shown in Physique 1F (data not shown), were similar to that of MKD1 cells. We decided to focus on the MKD1 clone as a potential model of early megakaryopoiesis because, similarly to MkPs and immature MKs, MKD1 displayed low AchE activity and low ploidy [9]. Moreover, as described below, expression of CD41 and 42b increases as MKD1 cells differentiate along the megakaryocytic lineage, as also reported for MkPs [9]. Open in a separate window Physique 1 MKD1 cell line exhibits.