Role of the 2 zebrafish survivin genes in vasculo-angiogenesis, neurogenesis, cardiogenesis and hematopoiesis

<p>Abstract</p> <p>Background</p> <p>Normal growth and development of organisms requires maintenance of a dynamic balance between systems that promote cell survival and those that induce apoptosis. The molecular mechanisms that regulate these processes remain poorly understood, and thus further <it>in vivo </it>study is required. Survivin is a member of the inhibitor of apoptosis protein (IAP) family, that uniquely also promotes mitosis and cell proliferation. Postnatally, survivin is hardly detected in most tissues, but is upregulated in all cancers, and as such, is a potential therapeutic target. Prenatally, survivin is also highly expressed in several tissues. Fully delineating the properties of survivin <it>in vivo </it>in mice has been confounded by early lethal phenotypes following <it>survivin </it>gene inactivation.</p> <p>Results</p> <p>To gain further insights into the properties of survivin, we used the zebrafish model. There are 2 zebrafish <it>survivin </it>genes (<it>Birc5a </it>and <it>Birc5b</it>) with overlapping expression patterns during early development, prominently in neural and vascular structures. Morpholino-induced depletion of <it>Birc5a </it>causes profound neuro-developmental, hematopoietic, cardiogenic, vasculogenic and angiogenic defects. Similar abnormalities, all less severe except for hematopoiesis, were evident with suppression of <it>Birc5b</it>. The phenotypes induced by morpholino knockdown of one <it>survivin </it>gene, were rescued by overexpression of the other, indicating that the <it>Birc5 </it>paralogs may compensate for each. The potent vascular endothelial growth factor (VEGF) also entirely rescues the phenotypes induced by depletion of either <it>Birc5a </it>and <it>Birc5b</it>, highlighting its multi-functional properties, as well as the power of the model in characterizing the activities of growth factors.</p> <p>Conclusion</p> <p>Overall, with the zebrafish model, we identify survivin as a key regulator of neurogenesis, vasculo-angiogenesis, hematopoiesis and cardiogenesis. These properties of survivin, which are consistent with those identified in mice, indicate that its functions are highly conserved across species, and point to the value of the zebrafish model in understanding the role of this IAP in the pathogenesis of human disease, and for exploring its potential as a therapeutic target.</p

Atypical hemolytic uremic syndrome in children: complement mutations and clinical characteristics

Item does not contain fulltextBACKGROUND: Mutations in complement factor H (CFH), factor I (CFI), factor B (CFB), thrombomodulin (THBD), C3 and membrane cofactor protein (MCP), and autoantibodies against factor H (alphaFH) with or without a homozygous deletion in CFH-related protein 1 and 3 (CFHR1/3) predispose development of atypical hemolytic uremic syndrome (aHUS). METHODS: Different mutations in genes encoding complement proteins in 45 pediatric aHUS patients were retrospectively linked with clinical features, treatment, and outcome. RESULTS: In 47% of the study participants, potentially pathogenic genetic anomalies were found (5xCFH, 4xMCP, and 4xC3, 3xCFI, 2xCFB, 6xalphaFH, of which five had CFHR1/3); four patients carried combined genetic defects or a mutation, together with alphaFH. In the majority (87%), disease onset was preceeded by a triggering event; in 25% of cases diarrhea was the presenting symptom. More than 50% had normal serum C3 levels at presentation. Relapses were seen in half of the patients, and there was renal graft failure in all except one case following transplant. CONCLUSIONS: Performing adequate DNA analysis is essential for treatment and positive outcome in children with aHUS. The impact of intensive initial therapy and renal replacement therapy, as well as the high risk of recurrence of aHUS in renal transplant, warrants further understanding of the pathogenesis, which will lead to better treatment options.01 augustus 201

Advances in our understanding of the pathogenesis of glomerular thrombotic microangiopathy

Glomerular thrombotic microangiopathy is a hallmark feature of haemolytic uraemic syndrome, the leading cause of acute renal failure in childhood. This paper is a review of the different mechanistic pathways that lead to this histological picture in the kidney. It will focus on atypical HUS and complement dysregulation, but will also highlight some other recent advances in our understanding of this condition, including the potential role of the molecule vascular endothelial growth factor- A (VEGF-A)

Integration of CNS survival and differentiation by HIF2α

Hypoxia-inducible factor (HIF) 1α and HIF2α and the inhibitor of apoptosis survivin represent prominent markers of many human cancers. They are also widely expressed in various embryonic tissues, including the central nervous system; however, little is known about their functions in embryos. Here, we show that zebrafish HIF2α protects neural progenitor cells and neural differentiation processes by upregulating the survivin orthologues birc5a and birc5b during embryogenesis. Morpholino-mediated knockdown of hif2α reduced the transcription of birc5a and birc5b, induced p53-independent apoptosis and abrogated neural cell differentiation. Depletion of birc5a and birc5b recaptured the neural development defects that were observed in the hif2α morphants. The phenotypes induced by HIF2α depletion were largely rescued by ectopic birc5a and birc5b mRNAs, indicating that Birc5a and Birc5b act downstream of HIF2α. Chromatin immunoprecipitation assay revealed that HIF2α binds to birc5a and birc5b promoters directly to modulate their transcriptions. Knockdown of hif2α, birc5a or birc5b reduced the expression of the cdk inhibitors p27/cdkn1b and p57/cdkn1c and increased ccnd1/cyclin D1 transcription in the surviving neural progenitor cells. The reduction in elavl3/HuC expression and enhanced pcna, nestin, ascl1b and sox3 expression indicate that the surviving neural progenitor cells in hif2α morphants maintain a high proliferation rate without terminally differentiating. We propose that a subset of developmental defects attributed to HIF2α depletion is due in part to the loss of survivin activity

aHUS caused by complement dysregulation: new therapies on the horizon

Atypical hemolytic uremic syndrome (aHUS) is a heterogeneous disease that is caused by defective complement regulation in over 50% of cases. Mutations have been identified in genes encoding both complement regulators [complement factor H (CFH), complement factor I (CFI), complement factor H-related proteins (CFHR), and membrane cofactor protein (MCP)], as well as complement activators [complement factor B (CFB) and C3]. More recently, mutations have also been identified in thrombomodulin (THBD), an anticoagulant glycoprotein that plays a role in the inactivation of C3a and C5a. Inhibitory autoantibodies to CFH account for an additional 5–10% of cases and can occur in isolation or in association with mutations in CFH, CFI, CFHR 1, 3, 4, and MCP. Plasma therapies are considered the mainstay of therapy in aHUS secondary to defective complement regulation and may be administered as plasma infusions or plasma exchange. However, in certain cases, despite initiation of plasma therapy, renal function continues to deteriorate with progression to end-stage renal disease and renal transplantation. Recently, eculizumab, a humanized monoclonal antibody against C5, has been described as an effective therapeutic strategy in the management of refractory aHUS that has failed to respond to plasma therapy. Clinical trials are now underway to further evaluate the efficacy of eculizumab in the management of both plasma-sensitive and plasma-resistant aHUS

Genetics and complement in atypical HUS

Central to the pathogenesis of atypical hemolytic uremic syndrome (aHUS) is over-activation of the alternative pathway of complement. Following the initial discovery of mutations in the complement regulatory protein, factor H, mutations have been described in factor I, membrane cofactor protein and thrombomodulin, which also result in decreased complement regulation. Autoantibodies to factor H have also been reported to impair complement regulation in aHUS. More recently, gain of function mutations in the complement components C3 and Factor B have been seen. This review focuses on the genetic causes of aHUS, their functional consequences, and clinical effect

DNA breakage, cytotoxicity, drug accumulation and retention in two human ovarian tumor cell lines AZ224 and AZ364 treated with adriamycine, modulated by verapamil.

We investigated the cytotoxicity of adriamycin in two human ovarian tumor cell lines, AZ224 and AZ364, by the MTT-test and we analysed the formation of DNA single-strand (SSB) and double-strand breaks (DSB) by means of the alkaline and neutral elution technique. The AZ364 cell line was 15 times more resistant to ADR (ID 50 = 10.0 μg/ml) than the AZ224 cell line (ID 50 = 0.66 μg/ml) after 1 hr of drug exposure. Immediately after exposure, we observed a biphasic dose response for SSB in the AZ224 cells over a concentration range of 0.1 to 32.0 μg/ml, while practically no DSB were found. Upon drug removal and incubation in drug-free medium, full repair of SSB was observed for an ADR concentration of 1 μg/ml. On the contrary, the DSB became significantly increased for all tested concentrations and persisted as observed after 3 hr and 7 hr in drug-free medium. The resistant cell line AZ 364 showed consistently less DNA breakage than the AZ 224 cell line. This inherent difference in sensitivity to ADR could, however, not be explained on the basis of the cellular pharmacokinetics of the drug. Verapamil induced a 3 to 4 fold potentiation of the ADR cytotoxicity in both cell lines after continuous exposure and was associated with an increase in DNA-breakage. The results of our study confirm that there is a lack of correlation between cytotoxicity of ADR and DNA strand breakage immediately after 1 hr of drug exposure. Instead, we emphasize the importance of the formation, extent and persistence of protein-associated DSB upon drug removal to the cytotoxic action of ADR in vitro.SCOPUS: ar.jinfo:eu-repo/semantics/publishe