A highly conserved multisubunit enzymic complex, SWI/SNF, participates in the regulation of eukaryote gene expression through its ability to remodel chromatin. While a single component of SWI/SNF, Swi2 or a related protein, can perform this function in vitro, the other components appear to modulate the activity and specificity of the complex in vivo. Here we describe the cloning of hELD/OSA1, a 189KDa human homologue of Drosophila Eld/Osa protein, a constituent of Drosophila SWI/SNF. By comparing conserved peptide sequences in Eld/Osa homologues we define three domains common to all family members. A putative DNA binding domain, or ARID (AT-rich DNA-interacting domain), may function in targetting SWI/SNF to chromatin. Two other domains unique to Eld/Osa proteins, EHD1 and EHD2, map to the C-teminus. We show that EHD2 mediates binding to Brahma-related gene 1 (BRG1), a human homologue of yeast Swi2. EHD1 and EHD2 also appear capable of interacting with each other. Using an antibody raised against EHD2 of hELD/OSA1, we detected Eld/Osa1 in endogenous SWI/SNF complexes derived from mouse brain.
Intracerebral haemorrhage (ICH) is a devastating condition with limited treatment options, and current understanding of pathophysiology is incomplete. Spontaneous cerebral bleeding is a characteristic of the human condition that has proven difficult to recapitulate in existing pre-clinical rodent models. Zebrafish larvae are frequently used as vertebrate disease models and are associated with several advantages, including high fecundity, optical translucency and non-protected status prior to 5 days post-fertilisation. Furthermore, other groups have shown that zebrafish larvae can exhibit spontaneous ICH. The aim of this study was to investigate whether such models can be utilised to study the pathological consequences of bleeding in the brain, in the context of pre-clinical ICH research. Here, we compared existing genetic (bubblehead) and chemically inducible (atorvastatin) zebrafish larval models of spontaneous ICH and studied the subsequent disease processes. Through live, non-invasive imaging of transgenic fluorescent reporter lines and behavioural assessment we quantified brain injury, locomotor function and neuroinflammation following ICH. We show that ICH in both zebrafish larval models is comparable in timing, frequency and location. ICH results in increased brain cell death and a persistent locomotor deficit. Additionally, in haemorrhaged larvae we observed a significant increase in macrophage recruitment to the site of injury. Live in vivo imaging allowed us to track active macrophage-based phagocytosis of dying brain cells 24 hours after haemorrhage. Morphological analyses and quantification indicated that an increase in overall macrophage activation occurs in the haemorrhaged brain. Our study shows that in zebrafish larvae, bleeding in the brain induces quantifiable phenotypic outcomes that mimic key features of human ICH. We hope that this methodology will enable the pre-clinical ICH community to adopt the zebrafish larval model as an alternative to rodents, supporting future high throughput drug screening and as a complementary approach to elucidating crucial mechanisms associated with ICH pathophysiology.
Application of tumor immunotherapy has achieved an unprecedented success in patients with hematopoietic malignancies. However, it remains challenging to treat the majority of solid tumors with immunotherapy due to low lymphocyte infiltration, treatment resistance, and immunosuppressive tumor microenvironment. Improving the clinical efficacy of immunotherapy in solid tumors requires a deeper understanding of immune evasion. Neuroblastoma is the most common extracranial tumor in children and is responsible for ~15% of childhood cancer-related deaths. MYCN is a member of the MYC oncogene family, and its aberrant expression in neuroblastoma predicts aggressive disease and poor prognosis. This largely results from the low infiltration rates of cytotoxic lymphocytes in MYCN-amplified neuroblastoma. Elucidation of the mechanism by which MYCN suppresses antitumor response in the neuroblastoma microenvironment will provide useful information to guide immunotherapy. Here we generated a compound transgenic zebrafish, Tg(dβh:MYCN;dβh:EGFP;lck:EGFP;CD4:mCherry), in which lymphocytes and tumor cells are differentially fluorescently labeled. We first monitored the infiltration of mCherry-labeled CD4+ T cells in EGFP-positive MYCN-overexpressing premalignant neural crests at 7, 14, and 21 days post fertilization (dpf). We found that at day 14 and 21, MYCN-overexpressing premalignant neural crests can attract a significantly higher number of lymphocytes, compared to control neural crests without MYCN overexpression. Interestingly, we also found the increased number of infiltrated T cells was MYCN dose dependent by using low MYCN-expressing transgenic fish, Tg(dβh:MYCN;dβh:mCherry;lck:EGFP). To determine if T-cell development is impacted, we imaged the thymus of MYCN-overexpressing or control fish at day 7, 14, and 21 dpf. We found that fluorescent intensity of thymus is significantly higher in MYCN-overexpressing fish compared to control fish. Taken together, our study identified MYCN-overexpressing premalignant neural crests can not only affect T-cell development but also attract T cells to disease site. We will perform further experiments to understand how and why MYCN-overexpressing premalignant neural crests impact T-cell development and which population of T cells is attracted to disease site. Citation Format: Xiaodan Qin, Andrew Lam, Xike Zhang, Adam Hurlstone, Hui Feng. Exploiting the zebrafish to study lymphocyte infiltration in MYCN-driven neuroblastoma [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B12.
Malignant melanoma is one of the most aggressive types of malignancies in humans resulting in 50,000 deaths worldwide annually. Fortuitously, malignant melanoma is highly immunogenic and it is now well established that the host immune system can detect and kill melanoma. T helper type-1 lymphocytes (TH1) play a pivotal role in inducing and maintaining anti-tumour immune responses. In melanoma patients, it has been observed that higher number of TH1 cells in the tumour micro-environment lead to better prognosis. In this study, using an autochthonous zebrafish melanoma model, when we forced the expression of interferon gamma (IFNg) locally in the tumour microenvironment, thereby potentially enhancing TH1 differentiation, we observed an inflammatory response against melanoma that eventually lead to complete tumour regression. Using transposon mediated BAC transgenesis, we have generated a Tg(cd4:mcherry) reporter line labelling CD4+ cells in zebrafish. By driving Human NRASQ61L in zebrafish melanocytes we have modelled melanoma in zebrafish and later when these fish developed tumours we forced the expression of IFNg in melanoma cells using a tamoxifen inducible LSL/CreERT2 system driven by mitfa minimal promoter. Experiments were performed using animals with and without CreERT2. Following tamoxifen administration, we observed a loss of pigmentation in all the IFNg induced tumours (n = 12) by 2 weeks post induction which gradually increased over the study period. Whereas no loss of pigmentation was observed in control tumours (n = 12) throughout the study period. At 9 weeks post induction, the study was terminated and tumours were analysed using histology. In tumours were IFNg was induced, we observed that the tumour tissue was now replaced with fibrotic tissue accompanied by a marked lymphocyte infiltration and patches of necrosis. However, new tumour nodules were also observed to develop in the vicinity of regressing nodules which are unpigmented and potentially hypo-immunogenic. We observed no signs of tumour regression in control tumours. Although preliminary, our data is very exciting and promising as it will open new avenues for developing combinatorial therapies in melanoma. Using a high throughput in-vivo model system such as zebrafish, it is an exciting proposition to test the impact of combining anti-PD1/PDL1 inhibitors with various cytokines/chemokines in inducing effective and sustained tumour regression in melanoma. Citation Format: Raghavendar Nagaraju, Christopher Dee, Helen Young, Jorge Barriuso, Christopher Secombes, Adam Hurlstone. Rewiring the cytokine network in melanoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4180.
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