Verhandelingen - Koninklijke Academie voor Geneeskunde van Belgie最新文献

Viruses in general, HIV in particular, use cellular proteins or cofactors to achieve their replication cycle. Our recent research efforts resulted in the identification and validation of two new cellular cofactors of HIV replication: LEDGF/p75 and transportin-SR2. LEDGF/p75 is a cellular transcriptional coactivator used by the virus to tether the preintegration complex onto the chromosome; transportin-SR2 is a cellular import factor used by the virus for nuclear import into the nucleus. After validation of LEDGF/p75 as an antiviral target, we initiated a drug discovery program to develop small molecule inhibitors of integrase-LEDGF/p75 interaction. Using molecular modeling, medicinal chemistry, crystallography and virology, our team developed LEDGINs, the first-in-class small molecule inhibitors of HIV targeting integrase/LEDGF/p75 interaction. As for transportin-SR2, this protein was identified by yeast-two-hybrid screening and validated as a nuclear import factor for HIV. A drug discovery program for inhibitors of nuclear import is ongoing. Together our research results provide a paradigm shift in antiviral research. Yes, small molecules can be developed inhibiting the protein-protein interaction between a viral protein and a cellular cofactor. In a broader perspective our research strongly supports the development of protein-protein interaction inhibitors as drugs.

While genetic factors play a role in the development of obesity, the dramatic increase of its prevalence in the past years strongly suggests that environmental factors are largely responsible. The wealth and variety of food supply available 24h/day and throughout the year, the change in dietary habits due to time constraints and the change in physical activity due to technological advances all create a 'toxic' environment responsible for obesity and eating habit disorders. This manuscript describes and discusses the results of a systematic review of environmental opportunities & obstacles for physical activity and dietary intake influencing the obesity epidemic among children and adolescents. Although evidence clearly shows the impact of the environment on obesity related lifestyle factors, evidence for effective strategies combating this obesogenic environment is very scarce. Interventions aiming to change environmental factors in order to reduce obesity may include taxes/subsidies encouraging healthy eating or physical activity, extra provision of sporting facilities, efforts to improve safety and accessibility of walking, cycling or play areas or attempting to influence social meanings/values attached to weight, food or physical activity. It is clear that some level of institutionalization of systems that support the desired changes is required to sustain environmental and social changes in the long-term. At last, it is important to note that better-designed and -conducted research on the true importance of the interaction between environmental factors and psychosocial factors, including the micro- and the macro-level, for obesogenic behavioral change is needed to reassure the success of large-scale environmental change interventions.

Infertility is a problem affecting many couples with a child wish. In about half of these couples a male factor is (co-) responsible for the fertility concern. For part of these patients a genetic factor will be the underlying cause of the problems. This paper gives an overview of the studies performed in the Department of Embryology and Genetics of the Vrije Universiteit Brussel and the Centre for Medical Genetics of UZ Brussel in order to gain more insight into the genetic causes of male infertility. The studies, focusing on men with fertility problems, can be subdivided into three groups: studies on deletions on the long arm of the Y chromosome, studies on X-linked genes and studies on autosomal genes. It is obvious that Yq microdeletions should be considered as a cause of male infertility. Only for patients with a complete AZFc deletion, a small number of spermatozoa can be retrieved. However, even for these patients assisted reproductive technologies are necessary. Complete AZF deletions are found in 4.6% of the patients visiting the centres for Reproductive Medicine and Medical Genetics of the UZ Brussel and for whom no other cause of the fertility problems have been detected. Taken into consideration this low prevalence of Yq microdeletions, it is obvious that also other factors, including genetic factors, must be causing fertility problems. Potentially, gr/gr deletions (partial deletions of the AZFc region) might influence the fertility status of the patients. It remains, however, unclear which of the genes located in the deleted regions are important for the progression of spermatogenesis, in case of partial or complete AZF deletions. In our studies we have also investigated mutations in genes located on the X chromosome. In analogy to the Y chromosome, the X chromosome is interesting in view of studying male infertility since men only have a single copy of the sex chromosomes. As a consequence, mutations in genes crucial for spermatogenesis will have an immediate impact on the sperm production. The genes NXF2, USP26 and TAF7L were investigated for the presence of mutations. All observed single nucleotide changes were also present in control samples, questioning their relationship with male infertility. We also studied five autosomal genes: SYCP3, MSH4, DNMT3L, STRA8 and ETV5. Only for the genes STRA8 and ETV5, changes were detected that were absent in a control population existing of men with normozoospermia. Functional analysis of the changes in ETV5 and the localization of the change observed in STRA8 showed that also these alterations were probably not the cause of the fertility problems in these men. It can be concluded that mutations are rarely detected in men with fertility problems. This low frequency of mutations has also been confirmed in several published studies. Therefore, further research is necessary to determine the impact of genetic causes on male infertility.

This research project aimed at evaluating the clinical and prognostic value of different molecules involved in signalling transduction pathways involved in melanoma progression. Vascular endothelial growth factor-C or VEGF-C induces lymphangiogenesis. This study showed high VEGF-C expression to be associated with the presence of a positive sentinel lymph node. The presence of VEGF-C expression in melanoma cells was associated with reduced disease free and overall survival. RhoC is important in the organization of the actin filamental system. We observed RhoC mRNA and protein expression to be upregulated in a highly metastatic melanoma cell line (DX3aza), whereas only low expression levels were found in a melanoma cell line with low proliferative and invasive capacity (MeWo). RhoC immunoreactivity in melanoma tissue was associated with high Breslow tumour thickness and the presence of ulceration. C-Ski and SnoN have been identified as negative regulators in the TGF-beta pathway. We found a significant association between the presence of nuclear c-Ski and thicker, ulcerated melanomas. SnoN expression was associated with the presence of ulceration and a positive sentinel lymph node. Epidermal Growth Factor Receptor (EGFR) expression has been associated with tumour progression and poor outcome in a variety of solid tumours, EGFR immunoreactivity was more frequently present in patients with a positive sentinel lymph node. EGFR gene amplification was not observed; however, the presence of polysomy was associated with higher Breslow tumour thickness. Treating BLM melanoma cells with different concentrations of cetuximab reduced the invasive capacity of the melanoma cells, without impact on cell viability and growth.

Development of obesity is associated with extensive modifications in adipose tissue involving adipogenesis, angiogenesis and extracellular matrix proteolysis. The fibrinolytic (plasminogen/plasmin) system contributes to these processes. The main physiological inhibitor of the fibrinolytic system, plasminogen activator inhibitor-1 (PAI-1), is expressed in murine and human adipose tissues, and high PAI-1 levels predispose to thrombotic complications. The potential role of PAI-1 in development of adipose tissue remains, however, enigmatic. We have used nutritionally induced obesity models in wild-type and transgenic mice to study the role of the fibrinolytic system in the development of obesity. Our main findings are: 1) Obesity is associated with markedly enhanced plasma levels of PAI-1; 2) The effect of PAI-1 on in vivo adipose tissue development is concentration-dependent; 3) PAI-1 does not play a significant role in adipogenesis but may affect angiogenesis; 4). Tissue-type plasminogen activator (t-PA), the main target of PAI-1, impairs adipose tissue development; 5) PAI-1 contributes to the deleterious effect of obesity on the outcome of thrombotic ischemic stroke; and 6) The use of synthetic low Mr inhibitors of PAI-1 may have the potential to reduce obesity. These studies thus support a role for fibrinolytic activity and suggest that its modulation may allow to affect development of adipose tissue.

Notch signalling is a critical mediator of T cell development. However, while this signalling pathway is essential, it is not sufficient to induce T cell fate into multipotent hematopoietic precursor cells. Although Notch signalling events are crucial at all of the initial stages of T-lineage differentiation, T cell development also depends on other regulatory factors that are required at precise levels in order to preserve the well-balanced network that drives this process. Miss-expression of one of the factors profoundly perturbs this balance and results in alternative lineage cell fate. In this process, Notch plays an essential role as a gate-keeper of T-lineage fidelity by either enforcing the T cell fate or by inducing cell death if alternative lineages are induced in its presence. Notch also plays a critical role in the further lineage choices that occur within the T cell lineage. Importantly however, this seems to be different between mouse and human. While in the mouse it is clear that TCR-alphabeta T cells are much more dependent on Notch signalling compared to TCR-gammadelta T cells, the requirement for Notch signalling during human T cell development seems to be the opposite for both T cell lineages. Thus, while it is clear that Notch signalling plays a critical role during the early stages of T cell development, further work is essential to delineate the precise molecular network that controls T cell differentiation and this might be different between mouse and human.

The progressive degeneration of motor neurons in amyotrophic lateral sclerosis (ALS) is a complex and multifactorial process. Both excitotoxicity (excessive stimulation of glutamate receptors) and a shortage of the vascular endothelial growth factor (VEGF) have been implicated in the disease pathogenesis. In this study, both disease mechanisms were further characterized and their therapeutic potential was evaluated. Motor neurons were found to be particularly vulnerable to AMPA receptor stimulation (one subtype of glutamate receptors) and the toxicity was initiated by the influx of calcium ions through the AMPA receptors. Only AMPA receptors that lack a certain subunit (GluR2) are permeable to calcium ions, and compared to other neurons motor neurons had low GluR2 levels. Reducing GluR2 levels aggravated motor neuron death in culture and accelerated the process of motor neuron degeneration in vivo. The regulation of GluR2 expression was investigated further. Astrocytes were found to influence neuronal GluR2 expression and thus their vulnerability to excitotoxicity. In addition, the growth factor VEGF, which could slow down motor neuron degeneration in rats, stimulated GluR2 expression in motor neurons and protected against excessive AMPA receptor stimulation, providing a link between two important disease mechanisms in ALS. Clinical trials with AMPA receptor antagonists and VEGF will hopefully lead to a better treatment of patients with ALS.

Marfan syndrome (MFS) is a systemic disorder of connective tissue with autosomal dominant inheritance. The diagnosis of MFS is based on the identification of a combination of clinical manifestations in the ocular, musculoskeletal, and cardiovascular organ systems defined in the Ghent Nosology (De Paepe et al, 1996). Confirmation of the diagnosis in an individual requires the presence of major clinical manifestations in at least two organ systems associated with involvement of a third organ system. In relatives of an affected proband, major involvement of one organ system and involvement of a second organ system confirms the diagnosis. Major clinical criteria are very specific for MFS and include a combination of (4 out of 8) skeletal manifestations, ectopia lentis, dural ectasia and dilatation or dissection of the ascending aorta. The prevalence of- and the guidelines for the assessment of each of these major criteria are well established. Minor clinical criteria are less typical, but their importance in the diagnostic process should not be underestimated. Unfortunately, figures on the prevalence as well as practical guidelines for the assessment of most minor criteria are lacking, especially for those involving the cardiovascular system. The major cardiovascular manifestation in MFS is a progressive dilatation of the ascending aorta, leading to aortic aneurysm formation and eventually to fatal aortic rupture or dissection. Aortic dissection in early adult life is the leading cause of death in MFS. Early diagnosis of individuals at risk of the disease is extremely important as timely treatment of cardiovascular complications has greatly improved life expectancy in MFS. Despite progress in medical and surgical treatment of aortic aneurysms, MFS continues to be associated with significant morbidity and mortality. This may be related to inadequate diagnosis or treatment, but also to the occurrence of cardiovascular problems in ageing MFS patients that were unrecognised until now, such as left ventricular (LV) dysfunction.This thesis is focused on the study of cardiovascular manifestations of MFS which localize beyond the aortic root and on the presently unknown relationship between the severity of the cardiovascular phenotype and the genotype. In the first part, we have studied the prevalence and diagnostic value of the following cardiovascular manifestations of MFS: mitral valve prolapse (MVP) and calcification of the mitral valve annulus, dilatation of the main pulmonary artery (MPA) and dilatation or dissection of the descending aorta. We found a significantly higher prevalence of MVP in MFS patients compared to normal controls, indicating that this feature is useful in the diagnostic evaluation of the condition. In contrast, calcification of the mitral valve annulus appears to be very uncommon, difficult to quantify and therefore not useful in the diagnosis of MFS. We also studied the dimension of the MPA in a series of MFS patients and de

In 1963 I started the Laboratory of Molecular Biology (LMB) at the University of Ghent. Molecular Biology was then a new scientific discipline. Nucleic acids (NA) could be sequenced, manipulated, and recombined to form genetic information which never before had existed. Cloning of DNA-segments allowed multiplying a single molecule a billion-fold. By 1975 recombinant DNA-technology had sufficiently progressed that one could start the pursuit of a medically important goal. Our choice was to go for Interferon, a mysterious substance which could protect against viral infection, and might possibly be used as an anti-cancer agent if available in unlimited quantities. Fortunately, Piet De Somer, then Rector of the KUL, was one of the pioneers in interferon research. He encouraged his young colleague Erik De Clercq to collaborate with us. Erik brought extensive interferon expertise and reagents to the collaboration. But molecular biologists work with NA and interferon is a protein. There was a missing link which was provided by Jean Content of the Brussels Pasteur Institute. Jean had developed a system to convert interferon mRNA into protein, which was send to Leuven for quantification. This close collaboration between 3 laboratories led in January 1980 to the cloning of the human fibroblast, now interferon-beta, gene, and to the primary structure of the protein. However, 2 months earlier, Tadatsugu Taniguchi had succeeded already to obtain such a clone. But we were the first to express the clone in E. coli, and this was the definite proof that the cloned gene coded for human interferon-beta.