http://repub.eur.nl/res/aut/14659/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/38538/ 2012-11-22T00:00:00Z Regulatory T (Treg) cells, characterized by expression of the transcription factor forkhead box P3 (Foxp3), maintain immune homeostasis by suppressing self-destructive immune responses. Foxp3 operates as a late-acting differentiation factor controlling Tregcell homeostasis and function, whereas the early Treg-cell-lineage commitment is regulated by the Akt kinase and the forkhead box O (Foxo) family of transcription factors. However, whether Foxo proteins act beyond the Treg-cell- commitment stage to control Tregcell homeostasis and function remains largely unexplored. Here we show that Foxo1 is a pivotal regulator of Tregcell function. Tregcells express high amounts of Foxo1 and display reduced T-cell-receptor-induced Akt activation, Foxo1 phosphorylation and Foxo1 nuclear exclusion. Mice with Treg-cell- specific deletion of Foxo1 develop a fatal inflammatory disorder similar in severity to that seen in Foxp3-deficient mice, but without the loss of Tregcells. Genome-wide analysis of Foxo1 binding sites reveals ∼300 Foxo1-bound target genes, including the pro-inflammatory cytokine Ifng, that do not seem to be directly regulated by Foxp3. These findings show that the evolutionarily ancient Akt-Foxo1 signalling module controls a novel genetic program indispensable for Tregcell function. http://repub.eur.nl/res/pub/26414/ 2011-07-01T00:00:00Z Resistance to the antiestrogen tamoxifen remains a major problem in the management of estrogen receptor-positive breast cancer. Knowledge on the resistance mechanisms is needed to develop more effective therapies. Breast cancer antiestrogen resistance 4 (BCAR4) was identified in a functional screen for genes involved in tamoxifen resistance. BCAR4 is expressed in 27% of primary breast tumors. In patients treated with tamoxifen for metastized disease high BCAR4 mRNA levels are associated with reduced clinical benefit and progression-free survival. Regarding tumor aggressiveness high BCAR4 mRNA levels are associated with a shorter metastasis free survival and overall survival. In the present study, we investigated the role of BCAR4 in endocrine resistance. Forced expression of BCAR4 in human ZR-75-1 and MCF7 breast cancer cells resulted in cell proliferation in the absence of estrogen and in the presence of various antiestrogens. Inhibition of estrogen receptor 1 (ESR1) expression with small interfering RNA (siRNA), implied that the BCAR4-induced mechanism of resistance is independent of ESR1. Highly conserved BCAR4 homologues of rhesus monkey, green monkey, and the less conserved common marmoset gene induced tamoxifen-resistant cell proliferation, in contrast to the distant BCAR4 homologues of bovine and rabbit. Injection of BCAR4-expressing ZR-75-1 cells into nude mice resulted in rapidly growing tumors. In silico analysis showed that BCAR4 mRNA is highly expressed in human placenta and oocyte, and absent in other normal tissues. In conclusion, BCAR4 is a strong transforming gene causing estrogen-independent growth and antiestrogen resistance, and induces tumor formation in vivo. Due to its restricted expression, BCAR4 may be a good target for treating antiestrogen-resistant breast cancer. http://repub.eur.nl/res/pub/16422/ 2009-04-06T00:00:00Z During development, Schwann cells (SCs) interpret different extracellular cues to regulate their migration, proliferation, and the remarkable morphological changes associated with the sorting, ensheathment, and myelination of axons. Although interactions between extracellular matrix proteins and integrins are critical to some of these processes, the downstream signaling pathways they control are still poorly understood. Integrin-linked kinase (ILK) is a focal adhesion protein that associates with multiple binding partners to link integrins to the actin cytoskeleton and is thought to participate in integrin and growth factor-mediated signaling. Using SC-specific gene ablation, we report essential functions for ILK in radial sorting of axon bundles and in remyelination in the peripheral nervous system. Our in vivo and in vitro experiments show that ILK negatively regulates Rho/Rho kinase signaling to promote SC process extension and to initiate radial sorting. ILK also facilitates axon remyelination, likely by promoting the activation of downstream molecules such as AKT/protein kinase B. http://repub.eur.nl/res/pub/18227/ 2009-03-16T00:00:00Z Background. Members of the calcium-activated chloride channel (CLCA) gene family have been suggested to possess a variety of functions including cell adhesion and tumor suppression. Expression of CLCA family members has mostly been analyzed in non-neural tissues. Here we describe the expression of mouse and human CLCA genes in the nervous system. Results. We show that from the six mouse CLCA family members only Clca1, Clca2 and Clca4 mRNAs are expressed in the adult brain, predominantly in olfactory ensheathing cells. During mouse nervous system development Clca1/2 is more widely expressed, particularly in cranial nerves, the diencephalon and in the cerebral cortex. While human CLCA2 and CLCA4 genes are widely expressed in brain, and at particularly high levels in the optic nerve, human CLCA3, the closest homologue of mouse Clca1, Clca2 and Clca4, is not expressed in the brain. Furthermore, we characterize the expression pattern of mouse Clca1/2 genes during embryonic development by in situ hybridization. Conclusion. The data published in this article indicate that within the nervous system mouse Clca1/2 genes are highly expressed in the cells ensheathing cranial nerves. Human CLCA2 and CLCA4 mRNAs are expressed at high level in optic nerve. High level expression of CLCA family members in mouse and human glial cells ensheathing nerves suggests a specific role for CLCA proteins in the development and homeostasis of these cells. http://repub.eur.nl/res/pub/12294/ 2008-05-14T00:00:00Z Breast cancer is one of the leading causes of death of women in western countries. It affects one out of eight females in the USA (1) and one out of nine females in The Netherlands (www.kankerregistratie.nl) during their lifetime. Many risk factors for breast cancer have been identified including gender, familial susceptibility, age, and exposure to hormones i.e. use of exogenous hormones, young age at menarge, and high age at menopause and first pregnancy (2). Familial breast cancer accounts for 5-10% of total breast cancer. The remaining 90-95% are called “sporadic”. Occasionally breast cancer also affects males (1% of the breast-cancer incidence in women). In The Netherlands there are approximately 12000 new cases and about 3300 deaths yearly as a result of the disease. Since 1994, the mortality has slightly decreased due to earlier detection, following the introduction of the national breast cancer-screening program, and better treatment strategies (http://www.rivm.nl). Breast cancer patients may be subjected to various treatments including surgery, radiation, chemotherapy, molecular targeted therapy, or endocrine (hormonal) therapy. Often treatment strategies are combined. Surgery forms a part of nearly every patient’s treatment for breast cancer, resulting in partial removal (lumpectomy) or total removal of the breast (mastectomy). Radiation may be used before or after surgery, and may accompany chemotherapy. In molecular targeted therapy, compounds like monoclonal antibodies or small tyrosine kinase inhibitors inhibit a specific target molecule. In contrast to conventional chemotherapy, which acts on all dividing cells generating toxic effects and damage of normal tissues, targeted drugs allow to hit, in a more specific manner, subpopulations of cells directly involved in tumor progression. Endocrine therapy works by interfering with the estrogen pathway that enhances cell-proliferation. It is applied for prevention, adjuvant therapy, and for treatment of metastatic cancers in patients with hormone receptorpositive tumors (3, 4). http://repub.eur.nl/res/pub/13163/ 2003-01-01T00:00:00Z The genetic hierarchy that controls myelination of peripheral nerves by Schwann cells includes the POU domain Oct-6/Scip/Tst-1and the zinc-finger Krox-20/Egr2 transcription factors. These pivotal transcription factors act to control the onset of myelination during development and tissue regeneration in adults following damage. In this report we demonstrate the involvement of a third transcription factor, the POU domain factor Brn-2. We show that Schwann cells express Brn-2 in a developmental profile similar to that of Oct-6 and that Brn-2 gene activation does not depend on Oct-6. Overexpression of Brn-2 in Oct-6-deficient Schwann cells, under control of the Oct-6 Schwann cell enhancer (SCE), results in partial rescue of the developmental delay phenotype, whereas compound disruption of both Brn-2 and Oct-6 results in a much more severe phenotype. Together these data strongly indicate that Brn-2 function largely overlaps with that of Oct-6 in driving the transition from promyelinating to myelinating Schwann cells. http://repub.eur.nl/res/pub/12878/ 2000-01-01T00:00:00Z The POU domain transcription factor Oct-6 is a major regulator of Schwann cell differentiation and myelination. During nerve development and regeneration, expression of Oct-6 is under the control of axonal signals. Identification of the cis-acting elements necessary for Oct-6 gene regulation is an important step in deciphering the complex signalling between Schwann cells and axons governing myelination. Here we show that a fragment distal to the Oct-6 gene, containing two DNase I-hypersensitive sites, acts as the Oct-6 Schwann cell-specific enhancer (SCE). The SCE is sufficient to drive spatially and temporally correct expression, during both normal peripheral nerve development and regeneration. We further demonstrate that a tagged version of Oct-6, driven by the SCE, rescues the peripheral nerve phenotype of Oct-6-deficient mice. Thus, our isolation and characterization of the Oct-6 SCE provides the first description of a cis-acting genetic element that responds to converging signalling pathways to drive myelination in the peripheral nervous system.