We observed an almost 2-fold reduction in number and a marked decrease in the size of granulocyte colony-forming units (CFU-Gs) derived from bone marrow (Figure 2A-B). suggest that Gli1 and Smoothened may not be functionally redundant, and direct GLI1 inhibitors may be needed to effectively block HH/GLI1 activity in human disease. Introduction The proliferation of hematopoietic stem cells (HSCs) and progenitors is tightly regulated during normal homeostasis. HSCs are normally quiescent in the adult mouse but they can be induced to proliferate in response to stress or cytokine stimulation. In contrast, progenitors are highly proliferative to maintain a constant supply of infection-fighting white blood cells. Precisely how HSC and progenitor proliferation are regulated is not completely understood, but recent data have implicated a role for developmental signaling pathways such as Wnt and Notch in the regulation of stem Rabbit Polyclonal to OR1A1 cell proliferation, self-renewal, and differentiation.1C4 The Hedgehog (Hh) signaling pathway in mammals consists of 3 closely related ligands, Sonic Hh (Shh), Indian Hh (Ihh), and Desert Hh (Dhh), that can each bind to the transmembrane protein Patched (Ptch). Upon ligand binding, Ptch inhibition of the positive effector Smoothened (Smo) is released and signaling is transduced. Three zinc finger transcription factors, Gli1, Gli2, and Gli3, lie downstream of Smo and mediate Hh’s effects. Gli1 is a positive effector of signaling, Gli3 is predominantly a transcriptional inhibitor, and Gli2 can function in both roles.5 The precise role of Hh signaling in normal hematopoiesis, however, is not known and the literature is contradictory. One group has reported that loss of Smo activity leads to a severe defect in HSC function,6 whereas others have reported a more modest phenotype,7 or none at all.8,9 All of these studies have focused primarily on the upstream modulators of pathway activity, Ptch and Smo. To better understand the role of Hh signaling in normal hematopoiesis, we have focused on the common downstream positive effector Gli1. Using a mouse model, we have analyzed the function of Gli1 in adult HSCs and myeloid progenitors. Our results demonstrate that this transcription factor is a key regulator of HSC and myeloid cell proliferation and differentiation, and that loss of impairs stress hematopoiesis. Methods Analysis of bone marrow fractions and cell sorting mice were originally obtained from Alexander Joyner (Memorial Sloan-Kettering Cancer Center), and the colony Benorylate was bred and maintained at Johns Hopkins University. Genotyping was performed by polymerase chain reaction (PCR) as previously described.10 Mice were housed in accordance with Johns Hopkins University Institutional Animal Care and Use Committee policy and fed mouse chow and water ad libitum. Mice used for analysis were between 8 and 12 weeks old. Bone marrow was flushed from femurs and tibia with staining media (phosphate-buffered saline supplemented with 2% fetal bovine serum) and labeled at 108 cells/mL in staining media with the following antibodies as indicated: CD34-allophycocyaninC, FcRCphycoerythrin (PE)C or Flt3-PEC, c-KitCallophycocyaninCAlexa Fluor 750C, Sca1CPECcyanin 7C, and biotin streptavidinCperidinin-chlorophyll-protein complexCcyanin 5.5Clabeled lineage cocktail (CD3e, Gr1, B220, Ter119) (eBioscience). Fractions were analyzed and sorted on a 2-laser FACSAria (BD Biosciences). Quantitative PCR Cell populations were isolated by fluorescence-activated cell sorting (FACS) as described in Analysis of bone marrow fractions and Benorylate cell sorting. RNA was isolated using RNAqueous (Ambion), and cDNA was made using Superscript II (Invitrogen) primed with random hexamers per the manufacturer’s protocol. Quantitative reverse-transcriptase PCR for was Benorylate performed using SYBR-green Master Mix (Applied Biosystems) with the following primers: (forward) 5-TAATGTTGATGAAAGCTGGCT-3 and (reverse) 5-ATGCGCTCAGGTCAAATTCAG-3 as described by Fleming et al and normalized to (4367659; Applied Biosystems).11 Predesigned Taqman real-time primer/probes sets for (Mm00432360_m1; Applied Biosystems), (Mm00_436031m1; Applied Biosystems), and 18sRNA (4319413E) were obtained and PCR was performed using TaqMan Universal Master Mix (Applied Biosystems) on Benorylate a I-Cycler Real-Time PCR machine (Bio-Rad). Expression levels were normalized to 18sRNA and compared with the threshold cycle method. Bone marrow transplantation Five hundred c-Kit+Sca1+Linneg (KSL) sorted cells from test, and values less than .05 were considered significant. Results Gli1 deficiency skews HSC and progenitor compartments mice, which are homozygous for a insertion in the first exon of (hereafter referred to as website; see the Supplemental Materials link at the top of the online article). We examined the expression of and the Hh target gene within the bone marrow cells of wild-type mice by quantitative reverse-transcriptionCPCR.