The cloche and spadetail Genes Differentially Affect Hematopoiesis and Vasculogenesis

Abstract

In vertebrates, hematopoietic and vascular progenitors develop from ventral mesoderm. The first primitive wave of hematopoiesis yields embryonic red blood cells, whereas progenitor cells of subsequent definitive waves form all hematopoietic cell lineages. In this report we examine the development of hematopoietic and vasculogenic cells in normal zebrafish and characterize defects in cloche and spadetail mutant embryos. The zebrafish homologs of lmo2, c-myb, fli1, flk1, and flt4 have been cloned and characterized in this study. Expression of these genes identifies embryonic regions that contain hematopoietic and vascular progenitor cells. The expression of c-myb also identifies definitive hematopoietic cells in the ventral wall of the dorsal aorta. Analysis of b316 mutant embryos that carry a deletion of the c-myb gene demonstrates that c-myb is not required for primitive erythropoiesis in zebrafish even though it is expressed in these cells. Both cloche and spadetail mutant embryos have defects in primitive hematopoiesis and definitive hematopoiesis. The cloche mutants also have significant decreases in vascular gene expression, whereas spadetail mutants expressed normal levels of these genes. These studies demonstrate that the molecular mechanisms that regulate hematopoiesis and vasculogenesis have been conserved throughout vertebrate evolution and the clo and spt genes are key regulators of these programs.

phospholipase C gamma-1is required downstream ofvascular endothelial growth factorduring arterial development

“…2e-h). Expression level of fli1 transcript (Thompson et al 1998) in the dorsal aorta and posterior cardinal vein does not appear to be affected in y10 mutant embryos (Fig. 2i,j), consistent with the equivalent level of fli1:egfp transgene expression in wild-type and mutant embryos (Fig.…”

Vascular endothelial growth factor receptor signaling is required for cardiac valve formation in zebrafish

“…Expression of VEGF-R2/flk-1, the target of AAC 789 and PTK 787, is seen weakly throughout the endocardium of the developing heart at 48 hpf (Fig. 4q), consistent with previous reports (Thompson et al, 1998). The defects in endocardial and myocardial patterning, as indicated by ectopic expression of both notch 1b and bmp-4, may disrupt cell-cell communication within the developing valve region and thereby disrupt cell fate decisions during valve development.…”

Migratory path of definitive hematopoietic stem/progenitor cells during zebrafish development

“…The preparation and sequence information of digoxigenin (DIG)-labeled antisense rag1 RNA are available in previous report. 27 c-myb (primers: 5Ј-cggcacagacacagtgtttacagta-3Ј/5Ј-gattctcgaaggcaactttggacct-3Ј) 28 was amplified by reverse transcriptase-polymerase chain reaction (RT-PCR) and subcloned into pGEM-T Easy vector (Promega, Madison, WI) for in vitro transcription. Stained embryos were imaged with Olympus DP70 camera on Olympus BX51 microscope.…”