Wang, Youdong

The zebrafish has emerged as an excellent model for cardiovascular research thanks to its ex-utero and rapid embryonic development, its embryonic transparent nature, and its capacity to survive in the absence of a functional cardiovascular system during the first week of development, which enables functional characterization of mutations that would otherwise induce lethality in traditional murine models. The aim of this project is to identify and characterize novel genes involved in zebrafish cardiovascular development using mutagenic gene trapping, a technique that generates random insertional mutations across the genome. We use the well-defined RP2 gene-breaking transposon system, which not only mutates, but also fluorescently tags the trapped gene product(s) (Clark, Nat Methods, 2011). RP2 also introduces loxP sites into the mutant locus, which can be used for Cre-mediated phenotype rescue by microinjection of Cre recombinase, or by crossing to tissue-specific Cre lines. From over 3000 RP2-injected embryos, 141 fish showed germline transmission. Among them, 51 expressed strong fluorescence in different tissues, including the heart, vessels, notochord, central nervous system (CNS), and eyes. Three cardiovascular lines were selected for phenotypic characterization and functional studies. RP2#C2 strain expressed fluorescence in the heart valves, CNS, eyes and pectoral fin buds. Inverse PCR in RP2#C2 demonstrated a trapped gene at meis4.1a, which encodes a homeobox transcription factor that has not been previously studied in zebrafish. RP2#121 strain expressed strong fluorescence in cardiac and skeletal muscles. RP2#91 strain showed expression in the vasculature and demonstrated a trapped gene at pdgfra. Homozygous RP2#91 mutants showed severe defects in the heart, blood flow, and other body parts including the head and musculature. We are currently creating a panel of tissue-specific Cre lines targeting tissues such as cardiomyocytes, endothelial cells and smooth muscle cells for spatiotemporal rescuing of the mutant phenotype. The generated zebrafish protein-trap lines are invaluable tools to annotate gene function, dissect the molecular mechanisms of cardiovascular development, and potentially serve as disease models.

Abstract HACS1 is a SH3 (Src homology 3) and SAM (sterile alpha motif) domain containing adaptor protein that is expressed in activated B and dendritic cells, is up-regulated by Interleukin 4 in the process of B cell activation and likely serves to dampen the immune response. To elucidate the function of HACS1, we generated HACS1 gene knockout mice by deletion of the SH3 and SAM domains. HACS1−/− mice were viable and fertile and had normal bone marrow B cell development and normal splenic T and B cell populations. However, adult HACS1−/− mice had increased numbers of peritoneal B1 cells (IgM+CD5+). Upon LPS plus BCR or TCR stimulations, splenic cells from HACS1−/− mice demonstrated an upregulation of activation markers with increased intensity of CD23 expression or increased population of CD69 positive cells. Purified B220+ splenic B cells from HACS1−/− mice showed increased cell proliferation upon BCR stimulation. Both T helper type 1 (Th1) and T helper type 2 (Th2) humoral responses were enhanced in HACS1−/− mice upon immunization with T cell-dependent antigen NP-KLH, which resulted in increased production of interferon-gamma (IFN-γ), anti-NP IgG2a and IL-4, as well as anti-NP IgG1 and IgE. Upon immunization with T cell-independent antigens such as TNP-LPS and TNP-Ficoll, HACS1−/− mice had increased production of anti-TNP IgM and IgG3 as compared to normal controls. The in vitro maturation of bone marrow-derived dentritic cells from HACS1−/− mice was similar to wild-type mice but HACS1−/− dentritic cells showed increased IL-12 production upon stimulation with anti-CD40 or LPS. There was no significant difference in antigen uptake by cultured dentritic cells from non-immunized wild-type or knockout mice. However, in immunized mice, an increase in antigen uptake in HACS1−/− dentritic cells was observed. We further demonstrate that the HACS1−/− B cells had increased tyrosine phosphorylation in the resting state. As deletion of the SH3 & SAM domains of HACS1 appears to generate a hypersensitive immune response, our results collectively support that HACS1 negatively regulates adaptive immunity.

Abstract Human chromosome 13q14 is one of the hotspots of chromosomal deletion in prostate cancer, multiple myeloma, and chronic lymphocytic leukemia. Chromosome Condensation 1-like (CHC1L) is an uncharacterized gene in this region. CHC1L is found within the smallest common region of loss of heterozygosity in prostate cancer, and its decreased expression is linked to pathogenesis and progression of both prostate cancer and multiple myeloma. In the present study, we describe the generation and characterization of Chc1L gene knockout mice. Knockout mice develop normally and display an exaggerated proliferative response to LPS stimulation of cultured bone marrow and spleen cells at ten weeks of age. At approximately two years of age, both homozygous and heterozygous mice have markedly increased incidence of tumorigenesis, 80% and 56% respectively, compared to wild-type mice, 26%. The tumors are distributed most commonly to the spleen, mesenteric lymph nodes, liver and small intestine. The morphologic and immunophenotypic features of the tumor cells are consistent with those of tissue histiocytes, and most Chc1L knockout and heterozygote mice succumb to either Histiocytic Sarcoma or Histiocyte-Associated Lymphoma. These data provide the first direct evidence that Chc1L is a tumor suppressor gene involved in suppression of histiocyte-rich neoplasms. Citation Format: David Spillane, Ding Yan Wang, Changxin Shi, Youdong Wang, Anthony Gramolini, Keith Stewart, Susan Newbigging, Mingyao Liu, Xiao-Yan Wen. Chc1L is a tumor suppressor involved in development of histiocyte-rich neoplasms. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr C41.

Hacs1, a SH3 and SAM domain‐containing adaptor protein, is up‐regulated by IL‐4 in activated B cells and strongly expressed in dendritic cells. To elucidate the function of Hacs1 in immune regulation, we generated Hacs1 − / − mice by deletion of the SH3 and SAM domains. Hacs1 − / − mice were viable and fertile and had normal bone marrow B‐cell development and normal splenic T‐ and B‐cell populations. However, adult Hacs1 − / − mice had increased peritoneal Bla cells (IgM + CD5 + ). On immunization with T‐cell‐independent antigen TNP‐Ficoll, Hacs1 − / − mice had increased production of anti‐TNP IgM and IgG3. Purified splenic B cells from Hacs1 − / − mice showed increased cell proliferation on BCR (B‐cell receptor) stimulation. We further demonstrate that the Hacs1 − / − B cells had increased global tyrosine phosphorylation, including tyrosine kinases Lyn and Akt. Both T‐helper type 1 (T h 1) and T‐helper type 2 (T h 2) humoral responses were enhanced in Hacs1 − / − mice. In vitro bone marrow‐derived Hacs1 − / − dendritic cells showed increased IL‐12 production on stimulation with ovalbumin (OVA). This study suggests that Hacs1 is an immunoinhibitory adaptor that might be a useful target for immune suppression therapy.—Wang, D., Stewart, A. K., Zhuang, L., Zhu, Y., Wang, Y., Shi, C., Keating, A., Slutsky, A., Zhang, H., Wen, X.‐Y. Enhanced adaptive immunity in mice lacking the immunoinhibitory adaptor Hacs1. FASEBJ. 24, 947–956 (20l0). www.fasebj.org