The zebrafish kidney marrow is considered to be the organ of definitive hematopoiesis, analogous to the mammalian bone marrow. We have sequenced 26,143 ESTs and isolated 304 cDNAs with putative full-length ORF from a zebrafish kidney marrow cDNA library. The ESTs formed 7,742 assemblies, representing both previously identified zebrafish ESTs (56%) and recently discovered zebrafish ESTs (44%). About 30% of these EST assemblies have orthologues in humans, including 1,282 disease-associated genes in the Online Mendelian Inheritance in Man (OMIM) database. Comparison of the effective and regulatory molecules related to erythroid functions across species suggests a good conservation from zebrafish to human. Interestingly, both embryonic and adult zebrafish globin genes showed higher homology to the human embryonic globin genes than to the human fetal͞adult ones, consistent with evo-devo correlation hypothesis. In addition, conservation of a whole set of transcription factors involved in globin gene switch suggests the regulatory network for such remodeling mechanism existed before the divergence of the teleost and the ancestor of mammals. We also carried out whole-mount mRNA in situ hybridization assays for 493 cDNAs and identified 80 genes (16%) with tissue-specific expression during the first five days of zebrafish development. Twenty-six of these genes were specifically expressed in hematopoietic or vascular tissues, including three previously unidentified zebrafish genes: coro1a, nephrosin, and dab2. Our results indicate that conserved genetic programs regulate vertebrate hematopoiesis and vasculogenesis, and support the role of the zebrafish as an important animal model for studying both normal development and the molecular pathogenesis of human blood diseases.

A treatment strategy that combines arsenic trioxide (ATO) with the tyrosine kinase inhibitor imatinib mesylate (STI571, Gleevec) appears to induce markedly more cell apoptosis than imatinib mesylate alone in chronic myeloid leukemia (CML). To understand the mechanisms underlying the synergistic/additive action of these agents, we applied cDNA microarrays, component plane presentation integrated self-organizing map (CPP-SOM), and methods of protein biochemistry to study cell apoptosis induced by imatinib mesylate, ATO, and the combination of the 2 agents in the CML cell line K562. Numerous features with temporospatial relationships were revealed, indicating the coordinated regulation of molecular networks from various aspects of proapoptotic and apoptotic activities in CML. Imatinib mesylate appears to induce mainly the intrinsic pathway of cell apoptosis, whereas ATO induces the endoplasmic reticulum (ER) stress-mediated pathway of cell apoptosis, and the combination of the 2 agents seems to more effectively induce the intrinsic, extrinsic, and ER stress-mediated pathways of cell apoptosis, which results in a more effective and efficient induction of programmed cell death in K562 cells. This finding appears to be supported also by data de- IntroductionAdvances in molecular pathogenesis have facilitated the development of therapeutic strategies targeted to molecular events critical for human malignancies. This is represented by the treatment of chronic myeloid leukemia (CML) with imatinib mesylate (STI571), a specifically designed inhibitor that targets the tyrosine kinase activity of the BCR-ABL protein and consequently induces apoptosis in vitro as well as in vivo in CML cells. [1][2][3][4][5][6] Recent clinical trials in the chronic phase of CML have also demonstrated the remarkable efficacy of this molecularly targeted agent to patients with CML. 7 However, a significant proportion of the treated patients with previously failed experiences of interferon therapy remained predominantly BCR-ABL ϩ , suggesting a risk of later relapse. 8 Furthermore, patients in the accelerated and blast-crisis phase revealed a high frequency of relapse or resistance to imatinib mesylate. 9-11 As a result, much interest is now focused on the development of combination therapies to improve response rates and prevent resistance or relapse. 12 Arsenic, the oldest and also the newest form of antileukemia drug, may promote apoptosis and exert anti-CML effects. 13 A treatment strategy that combines arsenic compounds that lower BCR-ABL levels, with imatinib mesylate that inhibits BCR-ABL tyrosine kinase activity, has indeed shown promising potential in inducing more apoptosis in BCR-ABL ϩ cells. [14][15][16] Clinical applications of similar strategies may potentially strengthen the curative effects of imatinib mesylate. To better evaluate additive or synergistic effects of the combination of ATO with imatinib mesylate in CML cells, and to develop more sophisticated clinical protocols, we treated the CML cell line K562 with ATO, imatinib...