Consequences of Interstrand Crosslinks in Hematopoiesis: Tipping the balance between senescence and proliferation

The molecular processes that drive leukemogenesis from senescent bone marrow are largely unknown. The aim of this thesis is to understand the molecular basis of BM senescence in response to DNA damage, and how these steps subsequently contribute to leukemogenesis. Ercc1 deficient mice are deficient in both NER and ICL repair and display signs of premature aging in the BM. Because Ercc1 is involved in the FA pathway of ICL repair we used this model to investigate the molecular mechanisms of BM failure and subsequent leukemogenesis as seen in FA. Important questions in this respect are: (i) Is BM failure specifi c to defective ICL repair, or to the overall aging phenotype (Chapter 2), (ii) what is the influence of Ercc1 levels on senescence in the hematopoietic system (Chapter 3), (iii) which tumor suppressor mechanisms are responsible for BM failure as seen in Ercc1 deficient mice (Chapter 4), and (iv) is the poor response to Epo specific to the lack of Fanconi proteins or secondary to senescence (Chapter 5). Finally, we investigated whether activation of p53 counteracts Wnt signaling (Chapter 6). In order to address these questions we analyzed FA deficient erythroblasts isolated from fetal liver (Chapter 5), compared the phenotypes of Ercc1-/-, Ercc1-/d and Ercc1d/d mice (Chapter 3), generated double knockout mice which lack either the tumor suppressor gene Cdkn2A (p16INK4A/p19Arf) or p53 in an Ercc1 hypomorph background (Chapter 4) and analyzed the effect of the Wnt signaling pathway in primary erythroblasts derived from fetal livers (Chapter 6)

Avian influenza a virus in wild birds in highly urbanized areas

Avian influenza virus (AIV) surveillance studies in wild birds are usually conducted in rural areas and nature reserves. Less is known of avian influenza virus prevalence in wild birds located in densely populated urban areas, while these birds are more likely to be in close contact with humans. Influenza virus prevalence was investigated in 6059 wild birds sampled in cities in the Netherlands between 2006 and 2009, and compared with parallel AIV surveillance data from low urbanized areas in the Netherlands. Viral prevalence varied with the level of urbanization, with highest prevalence in low urbanized areas. Within cities virus was detected in 0.5% of birds, while seroprevalence exceeded 50%. Ring recoveries of urban wild birds sampled for virus detection demonstrated that most birds were sighted within the same city, while few were sighted in other cities or migrated up to 2659 km away from the sample location in the Netherlands. Here we show that urban birds were infected with AIVs and that urban birds were not separated completely from populations of long-distance migrants. The latter suggests that wild birds in cities may play a role in the introduction of AIVs into cities. Thus, urban bird populations should not be excluded as a human-animal interface for influenza viruses

ICL-induced miR139-3p and miR199a-3p have opposite roles in hematopoietic cell expansion and leukemic transformation

Interstrand crosslinks (ICLs) are toxic DNA lesions that cause severe genomic damage during replication, especially in Fanconi anemia pathway-deficient cells. This results in progressive bone marrow failure and predisposes to acute myeloid leukemia (AML). The molecular mechanisms responsible for these defects are largely unknown. Using Ercc1- deficient mice, we show that Trp53 is responsible for ICL-induced bone marrow failure and that loss of Trp53 is leukemogenic in this model. In addition, Ercc1-deficient myeloid progenitors gain elevated levels of miR-139-3p and miR-199a-3p with age. These microRNAs exert opposite effects on hematopoiesis. Ectopic expression of miR-139-3p strongly inhibited proliferation of myeloid progenitors, whereas inhibition of miR-139-3p activity restored defective proliferation of Ercc1-deficient progenitors. Conversely, the inhibition of miR-199a-3p functions aggravated the myeloid proliferation defect in the Ercc1-deficient model, whereas its enforced expression enhanced proliferation of progenitors. Importantly, miR-199a-3p caused AML in a pre-leukemic mouse model, supporting its role as an onco-microRNA. Target genes include HuR for miR-139-3p and Prdx6, Runx1, and Suz12 for miR-199a-3p. The latter genes have previously been implicated as tumor suppressors in de novo and secondary AML. These findings show that, in addition to TRP53-controlled mechanisms, miR-139-3p and miR-199a-3p are involved in the defective hematopoietic function of ICL-repair deficient myeloid progenitors

Pancreatic cyst surveillance imposes low psychological burden

Background/Objectives: For the currently recommended pancreatic cyst surveillance to be feasible, participant adherence is a prerequisite. Our objective was to evaluate the psychological burden of pancreatic cyst surveillance from a participant's perspective. Methods: The present participant survey is part of an international cohort study (PACYFIC study, www.pacyfic.net), which prospectively records the outcome of surveillance of asymptomatic pancreatic cysts. Participants are invited to complete questionnaires before and during cyst surveillance. Results: 109 participants, 31 enrolled before and 78 during surveillance (median time since cyst diagnosis 16.5 (IQR 36) months), returned a total of 179 questionnaires. The majority indicated that surveillance reduces concerns of developing pancreatic cancer (82%), gives a sense of certainty (81%) and is a good method to detect cancer (91%). Participants already undergoing surveillance reported more negative aspects than those still to commence, like sleeping worse (30% vs 13%, P = 0.035), postponing plans (32% vs 13%, P = 0.031), and finding the follow-up burdensome (33% vs 13%, P = 0.044). Overall, the vast majority (94%) deemed advantages to outweigh disadvantages. Anxiety and depression scores were low (median Hospital Anxiety and Depression Scale 4 for anxiety (IQR 6), 2 for depression (IQR 5)). Conclusion: The psychological burden of pancreatic cyst surveillance is low. Therefore, participant adherence is expected to be high and annual surveillance seems feasible