title: Characterization of expanded intermediate cell mass in zebrafish chordin morphant embryos.
abstract: We investigated the mechanisms of intermediate cell mass (ICM) expansion in zebrafish chordin (Chd) morphant embryos and examined the role of BMPs in relation to this phenotype. At 24 h post-fertilization (hpf), the expanded ICM of embryos injected with chd morpholino (MO) (ChdMO embryos) contained a monotonous population of hematopoietic progenitors. In situ hybridization showed that hematopoietic transcription factors were ubiquitously expressed in the ICM whereas vascular gene expression was confined to the periphery. BMP4 (but not BMP2b or 7) and smad5 mRNA were ectopically expressed in the ChdMO ICM. At 48 hpf, monocytic cells were evident in both the ICM and circulation of ChdMO but not WT embryos. While injection of BMP4 MO had no effect on WT hematopoiesis, co-injecting BMP4 with chd MOs significantly reduced ICM expansion. Microarray studies revealed a number of genes that were differentially expressed in ChdMO and WT embryos and their roles in hematopoiesis has yet to be determined. In conclusion, the expanded ICM in ChdMO embryos represented an expansion of embryonic hematopoiesis that was skewed towards a monocytic lineage. BMP4, but not BMP2b or 7, was involved in this process. The results provide ground for further research into the mechanisms of embryonic hematopoietic cell expansion.
authors.affiliation: Stem Cell Institute, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Anskar Y H
authors.initials: AY
authors.lastname: Leung
authors.forename: Eric M
authors.initials: EM
authors.lastname: Mendenhall
authors.forename: Tommy T F
authors.initials: TT
authors.lastname: Kwan
authors.forename: Raymond
authors.initials: R
authors.lastname: Liang
authors.forename: Craig
authors.initials: C
authors.lastname: Eckfeldt
authors.forename: Eleanor
authors.initials: E
authors.lastname: Chen
authors.forename: Matthias
authors.initials: M
authors.lastname: Hammerschmidt
authors.forename: Suzanne
authors.initials: S
authors.lastname: Grindley
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Ekker
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Verfaillie
mesh_terms: D000818:Animals; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000502:physiology*; D002455:Cell Division; D004305:Dose-Response Relationship, Drug; D020869:Gene Expression Profiling; D006023:Glycoproteins / Q000502:physiology*; D006410:Hematopoiesis; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D015398:Signal Transduction; D015027:Zebrafish / Q000196:embryology*; D029961:Zebrafish Proteins
chemical_list: D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D029961:Zebrafish Proteins; C525813:bmp4 protein, zebrafish; C054234:chordin