Boris Jerchow

Negative Feedback Loop of Wnt Signaling through Upregulation of Conductin/Axin2 in Colorectal and Liver Tumors

ABSTRACT Activation of Wnt signaling through β-catenin/TCF complexes is a key event in the development of various tumors, in particular colorectal and liver tumors. Wnt signaling is controlled by the negative regulator conductin/axin2/axil, which induces degradation of β-catenin by functional interaction with the tumor suppressor APC and the serine/threonine kinase GSK3β. Here we show that conductin is upregulated in human tumors that are induced by β-catenin/Wnt signaling, i.e., high levels of conductin protein and mRNA were found in colorectal and liver tumors but not in the corresponding normal tissues. In various other tumor types, conductin levels did not differ between tumor and normal tissue. Upregulation of conductin was also observed in the APC-deficient intestinal tumors of Min mice. Inhibition of Wnt signaling by a dominant-negative mutant of TCF downregulated conductin but not the related protein, axin, in DLD1 colorectal tumor cells. Conversely, activation of Wnt signaling by Wnt-1 or dishevelled increased conductin levels in MDA MB 231 and Neuro2A cells, respectively. In time course experiments, stabilization of β-catenin preceded the upregulation of conductin by Wnt-1. These results demonstrate that conductin is a target of the Wnt signaling pathway. Upregulation of conductin may constitute a negative feedback loop that controls Wnt signaling activity.

Molecular evolution of a novel hyperactive Sleeping Beauty transposase enables robust stable gene transfer in vertebrates

The Sleeping Beauty (SB) transposon is a promising technology platform for gene transfer in vertebrates; however, its efficiency of gene insertion can be a bottleneck in primary cell types. A large-scale genetic screen in mammalian cells yielded a hyperactive transposase (SB100X) with ∼100-fold enhancement in efficiency when compared to the first-generation transposase. SB100X supported 35–50% stable gene transfer in human CD34+ cells enriched in hematopoietic stem or progenitor cells. Transplantation of gene-marked CD34+ cells in immunodeficient mice resulted in long-term engraftment and hematopoietic reconstitution. In addition, SB100X supported sustained (>1 year) expression of physiological levels of factor IX upon transposition in the mouse liver in vivo. Finally, SB100X reproducibly resulted in 45% stable transgenesis frequencies by pronuclear microinjection into mouse zygotes. The newly developed transposase yields unprecedented stable gene transfer efficiencies following nonviral gene delivery that compare favorably to stable transduction efficiencies with integrating viral vectors and is expected to facilitate widespread applications in functional genomics and gene therapy.

The role of Axin2 in calvarial morphogenesis and craniosynostosis

Axin1 and its homolog Axin2/conductin/Axil are negative regulators of the canonical Wnt pathway that suppress signal transduction by promoting degradation of β-catenin. Mice with deletion of Axin1 exhibit defects in axis determination and brain patterning during early embryonic development. We show that Axin2 is expressed in the osteogenic fronts and periosteum of developing sutures during skull morphogenesis. Targeted disruption of Axin2 in mice induces malformations of skull structures, a phenotype resembling craniosynostosis in humans. In the mutants, premature fusion of cranial sutures occurs at early postnatal stages. To elucidate the mechanism of craniosynostosis, we studied intramembranous ossification in Axin2-null mice. The calvarial osteoblast development is significantly affected by the Axin2 mutation. The Axin2 mutant displays enhanced expansion of osteoprogenitors, accelerated ossification, stimulated expression of osteogenic markers and increases in mineralization. Inactivation of Axin2 promotes osteoblast proliferation and differentiation in vivo and in vitro. Furthermore, as the mammalian skull is formed from cranial skeletogenic mesenchyme, which is derived from mesoderm and neural crest, our data argue for a region-specific effect of Axin2 on neural crest dependent skeletogenesis. The craniofacial anomalies caused by the Axin2 mutation are mediated through activation of β-catenin signaling, suggesting a novel role for the Wnt pathway in skull morphogenesis.

Reciprocal Requirements for EDA/EDAR/NF-κB and Wnt/β-Catenin Signaling Pathways in Hair Follicle Induction

Wnt/beta-catenin and NF-kappaB signaling mechanisms provide central controls in development and disease, but how these pathways intersect is unclear. Using hair follicle induction as a model system, we show that patterning of dermal Wnt/beta-catenin signaling requires epithelial beta-catenin activity. We find that Wnt/beta-catenin signaling is absolutely required for NF-kappaB activation, and that Edar is a direct Wnt target gene. Wnt/beta-catenin signaling is initially activated independently of EDA/EDAR/NF-kappaB activity in primary hair follicle primordia. However, Eda/Edar/NF-kappaB signaling is required to refine the pattern of Wnt/beta-catenin activity, and to maintain this activity at later stages of placode development. We show that maintenance of localized expression of Wnt10b and Wnt10a requires NF-kappaB signaling, providing a molecular explanation for the latter observation, and identify Wnt10b as a direct NF-kappaB target. These data reveal a complex interplay and interdependence of Wnt/beta-catenin and EDA/EDAR/NF-kappaB signaling pathways in initiation and maintenance of primary hair follicle placodes.

Transposon-mediated transgenesis, transgenic rescue, and tissue-specific gene expression in rodents and rabbits

Germline transgenesis is an important procedure for functional investigation of biological pathways, as well as for animal biotechnology. We have established a simple, nonviral protocol in three important biomedical model organisms frequently used in physiological studies. The protocol is based on the hyperactive Sleeping Beauty transposon system, SB100X, which reproducibly promoted generation of transgenic founders at frequencies of 50–64, 14–72, and 15% in mice, rats, and rabbits, respectively. The SB100X‐mediated transgene integrations are less prone to genetic mosaicism and gene silencing as compared to either the classical pronuclear injection or to lentivirus‐mediated transgenesis. The method was successfully applied to a variety of transgenes and animal models, and can be used to generate founders with single‐copy integrations. The transposon vector also allows the generation of transgenic lines with tissue‐specific expression patterns specified by promoter elements of choice, exemplified by a rat reporter strain useful for tracking serotonergic neurons. As a proof of principle, we rescued an inborn genetic defect in the fawn‐hooded hypertensive rat by SB100X transgenesis. A side‐by‐side comparison of the SB100X‐ and piggyBac‐based protocols revealed that the two systems are complementary, offering new opportunities in genome manipulation.—Katter, K., Geurts, A. M., Hoffmann, O., Mátés, L., Landa, V., Hiripi, L., Moreno, C., Lazar, J., Bashir, S., Zidek, V., Popova, E., Jerchow, B., Becker, K., Devaraj, A., Walter, I., Grzybowksi, M., Corbett, M., Rangel Filho, A., Hodges, M. R., Bader, M., Ivics, Z., Jacob, H. J., Pravenec, M., Bősze, Z., Rülicke, T., Izsvák, Z. Transposon‐mediated transgenesis, transgenic rescue, and tissue‐specific gene expression in rodents and rabbits. FASEB J. 27, 930–941 (2013). www.fasebj.org

Abstract 2689: First MACC1 transgenic mice demonstrate tumor progression via the newly discovered MACC1/Nanog/Oct4 axis

We have previously identified the gene Metastasis-Associated in Colon Cancer 1 (MACC1). MACC1 acts a strong prognostic biomarker for colorectal cancer metastasis and patient survival. Meanwhile, MACC1 has been established as a biomarker for tumor progression, metastasis and patient survival for a broad variety of solid cancer types. Here, we report for the first time the generation of transgenic mouse models for MACC1. We generated mice with transgenic overexpression of MACC1 in the intestine driven by the villin promoter (vil-MACC1) and crossed them with ApcMin mice (vil-MACC1/ApcMin). vil-MACC1/ApcMin mice significantly increased the total number of tumors (P = 0.0056). This was particularly apparent in large sized tumors (≥ 3 mm diameter; P = 0.0024). A detailed histopathological analysis of these lesions demonstrated that the tumors from the vil-MACC1/ApcMin mice had a more invasive phenotype together with an accelerated adenoma-carcinoma-sequence. Consequently, vil-MACC1/ApcMin mice showed a significantly reduced survival time as compared to ApcMin mice (P = 0.03). Molecular analysis revealed an increased Wnt and pluripotency signaling in the tumors of vil-MACC1/ApcMin mice. Specifically, we observed a prominent upregulation of the pluripotency markers Oct4 and Nanog in these tumors as compared to ApcMin controls. Finally, we could also validate that Oct4 and Nanog are regulated by MACC1 in vitro, and strongly correlate with MACC1 levels in a cohort of 60 tumors of colorectal cancer patients (r = 0.7005 and r = 0.6808, respectively; P > 0.0001 and P > 0.0002, respectively). Taken together, we provide first evidence that MACC1-induced tumor progression acts, at least in part, via the newly discovered MACC1/Nanog/Oct4 axis. The evidence is accumulated from experiments in cell culture, MACC1 transgenic animals as well as colorectal cancer patients. This is the first time that the function of MACC1 is linked to pathways crucial in cancer stem cells. Based on the hypothesis that cancer stem cells are the main engine behind tumor progression and metastasis, these findings might have important therapeutic implications. Specifically, MACC19s relevance as a biomarker might further be augmented by focusing on its expression in cancer stem cells. Furthermore, the connection of MACC1 with Oct4 and Nanog might offer novel options for therapeutic intervention to restrict tumor progression. Citation Format: Clara Lemos, Markus S. Hardt, Manisha Juneja, Cynthia Voss, Susann Forster, Boris Jerchow, Wolfram Haider, Hendrik Blaker, Ulrike S. Stein. First MACC1 transgenic mice demonstrate tumor progression via the newly discovered MACC1/Nanog/Oct4 axis. [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 2689.

Global Increase of p16INK4a in APC-Deficient Mouse Liver Drives Clonal Growth of p16INK4a-Negative Tumors

Reduction of β-catenin (CTNNB1) destroying complex components, for example, adenomatous polyposis coli (APC), induces β-catenin signaling and subsequently triggers activation of genes involved in proliferation and tumorigenesis. Though diminished expression of APC has organ-specific and threshold-dependent influence on the development of liver tumors in mice, the molecular basis is poorly understood. Therefore, a detailed investigation was conducted to determine the underlying mechanism in the development of liver tumors under reduced APC levels. Mouse liver at different developmental stages was analyzed in terms of β-catenin target genes including Cyp2e1, Glul, and Ihh using real-time RT-PCR, reporter gene assays, and immunohistologic methods with consideration of liver zonation. Data from human livers with mutations in APC derived from patients with familial adenomatous polyposis (FAP) were also included. Hepatocyte senescence was investigated by determining p16INK4a expression level, presence of senescence-associated β-galactosidase activity, and assessing ploidy. A β-catenin activation of hepatocytes does not always result in β-catenin positive but unexpectedly also in mixed and β-catenin–negative tumors. In summary, a senescence-inducing program was found in hepatocytes with increased β-catenin levels and a positive selection of hepatocytes lacking p16INK4a, by epigenetic silencing, drives the development of liver tumors in mice with reduced APC expression (Apc580S mice). The lack of p16INK4a was also detected in liver tumors of mice with triggers other than APC reduction. Implications: Epigenetic silencing of p16Ink4a in selected liver cells bypassing senescence is a general principle for development of liver tumors with β-catenin involvement in mice independent of the initial stimulus. Mol Cancer Res; 13(2); 239–49. ©2014 AACR.

Transgenic Technology meeting 2008 in Toronto, Canada: a meeting report

In a history that goes back to 1999, the Transgenic Technology meetings started out in Sweden and over the years began to attract a growing community of technicians and researchers mainly from Europe. As the meetings started to attract an expanding worldwide audience, the community decided to found the International Society for Transgenic Technologies at the Barcelona meeting in 2005. The 2007 convention was held at Brisbane, Australia, and in 2008, the 8th Transgenic Technology meeting was held for the second time on behalf of ISTT and for the second time outside of Europe in Toronto, Canada. Due to its excellent program with over 400 participants the meeting was able to attract the highest number of delegates of all past TT meetings. With extended times for plenary discussions about technical and organizational aspects, as well as top level scientific presentations, both technicians and scientists enjoyed this as an extremely fruitful meeting from which they could take home solutions for daily routines as well as new insights and ideas for coming projects.

Guidelines on severity assessment and classification of genetically altered mouse and rat lines

Genetic alterations can unpredictably compromise the wellbeing of animals. Thus, more or less harmful phenotypes might appear in the animals used in research projects even when they are not subjected to experimental treatments. The severity classification of suffering has become an important issue since the implementation of Directive 2010/63/EU on the protection of animals used for scientific purposes. Accordingly, the breeding and maintenance of genetically altered (GA) animals which are likely to develop a harmful phenotype has to be authorized. However, a determination of the degree of severity is rather challenging due to the large variety of phenotypes. Here, the Working Group of Berlin Animal Welfare Officers (WG Berlin AWO) provides field-tested guidelines on severity assessment and classification of GA rodents. With a focus on basic welfare assessment and severity classification we provide a list of symptoms that have been classified as non-harmful, mild, moderate or severe burdens. Corresponding monitoring and refinement strategies as well as specific housing requirements have been compiled and are strongly recommended to improve hitherto applied breeding procedures and conditions. The document serves as a guide to determine the degree of severity for an observed phenotype. The aim is to support scientists, animal care takers, animal welfare bodies and competent authorities with this task, and thereby make an important contribution to a European harmonization of severity assessments for the continually increasing number of GA rodents.

TT2016 meeting report on the 13th Transgenic Technology meeting in Prague, Czech Republic

The TT2016 13th meeting of the International Society for Transgenic Technologies (ISTT) was held in the beautiful, historic city of Prague, Czech Republic on March 20–23, 2016. The meeting was hosted by Radislav Sedlacek (chair, Institute of Molecular Genetics of the ASCR, Prague, Czech Republic) in association with the Czech Academy of Sciences. This meeting assembled more participants than any of the past TT meetings with a total of more than 700 researchers, students and technicians from close to 40 countries around the world. The venue for the meeting was the very modern Clarion Congress Hotel Prague and was organized by Guarant International who did a superlative job and who were continuously available to be of service to delegates, speakers and vendors resulting in a smooth, well-run conference. CRISPR/Cas technology continues to be a major focus of our meetings as evidenced by its inclusion in a number of talks in several of the 16 varied sessions over the course of the three plus day conference. Other topics under the umbrella of transgenic technology ranged from new approaches in designing CRISPR/ Cas reagents to nanoinjection of nucleases into hundreds of cells at once to large animal technology. Presentations covered the use of the epigenome to target the ‘‘regulome’’; examination of non-coding regions of the genome; phenotypic analysis by large consortia; methods for increasing the number of ovulated mouse oocytes; gene drive advances; noninjection techniques; and the history and ethics of using guided nuclease technology. Overall, the scientific program was exceptional! There were a number of new initiatives at TT2016. We had orbis pictus lectures—lectures designed to use pictures and clear descriptions to demonstrate answers to a problem. Also, for the first time, we had concurrent sessions where delegates chose whether to hear about ethics in animal use, or new injection and superovulation techniques. Introduced this year, the Opening S. Tamowski (&) J. Luo University of Utah, Salt Lake City, UT, USA e-mail: tamowski@genetics.utah.edu