E. Elizabeth Patton

Bio: E. Elizabeth Patton is an academic researcher from Howard Hughes Medical Institute. The author has contributed to research in topics: Zebrafish & Gene knockdown. The author has an hindex of 4, co-authored 5 publications receiving 1295 citations. Previous affiliations of E. Elizabeth Patton include Boston Children's Hospital.

The art and design of genetic screens: zebrafish

Abstract: Inventive genetic screens in zebrafish are revealing new genetic pathways that control vertebrate development, disease and behaviour. By exploiting the versatility of zebrafish, biological processes that had been previously obscured can be visualized and many of the responsible genes can be isolated. Coupled with gene knockdown and overexpression technologies, and small-molecule-induced phenotypes, genetic screens in zebrafish provide a powerful system by which to dissect vertebrate gene function and gene networks.

The zebrafish as a model organism to study development of the immune system.

Abstract: Publisher Summary Early events in the development of the primitive and definitive blood forming system are still poorly understood. Additionally, the specification of both B and T cells occurs during embryogenesis and, given the completion of this process before birth, are difficult to study in mammals by forward genetics. Historically, the major strength of the zebrafish has been the opportunity it offered to carry forward genetic screens in a vertebrate organism in a relatively restricted space. Establishing the zebrafish as a model system for the study of the immune system will provide an alternative and complementary tool to the use of forward genetic screens in mice. Rapid advances in a variety of fields have allowed the zebrafish to become a more versatile tool for immunology.

Taking Human Cancer Genes to the Fish: A Transgenic Model of Melanoma in Zebrafish

Abstract: MELANOMA is an aggressive, and often deadly, cancer of the skin. In one year alone in the United States, over 50,000 people are diagnosed with melanoma, from which over 7000 people die.1 Despite an unprecedented understanding of cancer genetics and development, the incidence of melanoma continues to rise each year and melanoma remains a disease for which few treatments are effective.2 Once the disease is metastatic, the average person survives less than 8 months, often enduring gruelling treatments with minimal effectiveness. Human genetic studies, coupled with Xiphophorus and mouse melanoma models, point to the activation of the RAS kinase pathway and the loss of the INK4a/ARF locus as signature genetic events in melanoma.3–5 The INK4a/ARF locus encodes two tumor-suppressors: p16INK4a that acts in the Rb-pathway to inhibit progression through G1-phase, and p14ARF that acts in the p53 pathway to inhibit p53 function.6,7 A significant recent finding by The Cancer Genome Project, The Wellcome Trust Sanger Institute, identified mutations in the BRAF kinase in 66% of melanomas.8,9 The most common mutation, V600E, is found in a remarkable 80% of cases, and causes constitutive kinase activation and mitogen activated protein kinase (MAPK) pathway stimulation.8,10 Activating BRAF mutations are also found in nevi, a nonmalignant precursor lesion,11 and may correlate with proliferating versus dormant nevi.12 Further understanding of the in vivo significance of activating BRAF mutations would require an animal model. We set out to generate a zebrafish model of BRAF to gain a deeper understanding of the gene–gene and gene–environment interactions that lead to melanoma, and ultimately identify chemical inhibitors of melanoma progression.

Braf expression in zebrafish and uses thereof

Abstract: The present invention discloses a transgenic zebrafish that express activated BRAF specifically in melanocytes and its uses in screening for agents that can be used to treat melanomas or screening for agents that aggravate or induce melanomas.

BRAFE600-associated senescence-like cell cycle arrest of human naevi

Abstract: Cellular senescence, a growth-arrest program that limits the lifespan of mammalian cells and prevents unlimited cell proliferation, is attracting considerable interest because of its links to tumour suppression. Using a mouse model in which the oncogene Ras is activated in the haematopoietic compartment of bone marrow, Braig et al. show that cellular senescence can block lymphoma development. Genetic inactivation of the histone methyltransferase Suv39h1 that controls senescence by ‘epigenetic’ modification of DNA-associated proteins, or a pharmacological approach that mimics loss of this enzyme, allow the formation of malignant lymphomas in response to oncogenic Ras. This work has important implications for both tumour development and tumour therapy. Michaloglou et al. report that oncogene-induced senescence may be a physiologically important process in humans, keeping moles in a benign state for many years: unchecked they develop into malignant melanomas. Chen et al. also find that cellular senescence blocks tumorigenesis in vivo: they show that acting together, the p53 tumour suppressor and the cellular senescence system can prevent prostate cancer induction in mice by the PTEN mutation. Collado et al. show that cellular senescence is a defining feature of Ras-initiated premalignant tumours; this could prove valuable in the diagnosis and prognosis of cancer. See the web focus . Most normal mammalian cells have a finite lifespan1, thought to constitute a protective mechanism against unlimited proliferation2,3,4. This phenomenon, called senescence, is driven by telomere attrition, which triggers the induction of tumour suppressors including p16INK4a (ref. 5). In cultured cells, senescence can be elicited prematurely by oncogenes6; however, whether such oncogene-induced senescence represents a physiological process has long been debated. Human naevi (moles) are benign tumours of melanocytes that frequently harbour oncogenic mutations (predominantly V600E, where valine is substituted for glutamic acid) in BRAF7, a protein kinase and downstream effector of Ras. Nonetheless, naevi typically remain in a growth-arrested state for decades and only rarely progress into malignancy (melanoma)8,9,10. This raises the question of whether naevi undergo BRAFV600E-induced senescence. Here we show that sustained BRAFV600E expression in human melanocytes induces cell cycle arrest, which is accompanied by the induction of both p16INK4a and senescence-associated acidic β-galactosidase (SA-β-Gal) activity, a commonly used senescence marker. Validating these results in vivo, congenital naevi are invariably positive for SA-β-Gal, demonstrating the presence of this classical senescence-associated marker in a largely growth-arrested, neoplastic human lesion. In growth-arrested melanocytes, both in vitro and in situ, we observed a marked mosaic induction of p16INK4a, suggesting that factors other than p16INK4a contribute to protection against BRAFV600E-driven proliferation. Naevi do not appear to suffer from telomere attrition, arguing in favour of an active oncogene-driven senescence process, rather than a loss of replicative potential. Thus, both in vitro and in vivo, BRAFV600E-expressing melanocytes display classical hallmarks of senescence, suggesting that oncogene-induced senescence represents a genuine protective physiological process.

Animal models of human disease: zebrafish swim into view.

Abstract: Despite the pre-eminence of the mouse in modelling human disease, several aspects of murine biology limit its routine use in large-scale genetic and therapeutic screening. Many researchers who are interested in an embryologically and genetically tractable disease model have now turned to zebrafish. Zebrafish biology allows ready access to all developmental stages, and the optical clarity of embryos and larvae allow real-time imaging of developing pathologies. Sophisticated mutagenesis and screening strategies on a large scale, and with an economy that is not possible in other vertebrate systems, have generated zebrafish models of a wide variety of human diseases. This Review surveys the achievements and potential of zebrafish for modelling human diseases and for drug discovery and development.

The essence of senescence

Abstract: Almost half a century after the first reports describing the limited replicative potential of primary cells in culture, there is now overwhelming evidence for the existence of “cellular senescence” in vivo. It is being recognized as a critical feature of mammalian cells to suppress tumorigenesis, acting alongside cell death programs. Here, we review the various features of cellular senescence and discuss their contribution to tumor suppression. Additionally, we highlight the power and limitations of the biomarkers currently used to identify senescent cells in vitro and in vivo.

BrafV600E cooperates with Pten loss to induce metastatic melanoma

Abstract: Mutational activation of BRAF is the earliest and most common genetic alteration in human melanoma. To build a model of human melanoma, we generated mice with conditional melanocyte-specific expression of BRaf(V600E). Upon induction of BRaf(V600E) expression, mice developed benign melanocytic hyperplasias that failed to progress to melanoma over 15-20 months. By contrast, expression of BRaf(V600E) combined with Pten tumor suppressor gene silencing elicited development of melanoma with 100% penetrance, short latency and with metastases observed in lymph nodes and lungs. Melanoma was prevented by inhibitors of mTorc1 (rapamycin) or MEK1/2 (PD325901) but, upon cessation of drug administration, mice developed melanoma, indicating the presence of long-lived melanoma-initiating cells in this system. Notably, combined treatment with rapamycin and PD325901 led to shrinkage of established melanomas. These mice, engineered with a common genetic profile to human melanoma, provide a system to study melanoma's cardinal feature of metastasis and for preclinical evaluation of agents designed to prevent or treat metastatic disease.