Bulletin et memoires de l'Academie royale de medecine de Belgique最新文献

The possibilities for testing and screening for genes involved in inherited diseases or susceptibility to diseases have increased spectacularly. Combined with a revolution in the availability of sophisticated new technologies for testing, the question arises how will we be able to continue to provide quality services to our customers ? Who will provide these ? Will it be the centres, as we know them today, or will DTC take gradually over this service ? Will the quality criteria, as established today before tests are made available, still be applicable and how will these new services be able to contribute to an increasing and coordinated collection of global information on genetic diversity and on the pathogenic changes in the human genome? As stated in the Bioethics Convention of the European Council and explicited in the recent recommendations from the House of Lords of the UK on Genomic Medicine, we will need a major effort of the European Commission/of our governments, to implement a series of measures which will allow the correct and quality assured introduction into practice of the genetic knowledge that is being generated. Only then will all individuals and the scientific community be able to benefit from our services.

Mitochondria are not only the cell's powerhouse; they also constitute the weapon store for cellular suicide. In response to multiple distinct insults, mitochondrial membranes are permeabilized in a highly regulated fashion. Mitochondrial outer membrane permeabilization results in the cytosolic release of several factors that are normally secluded within the mitochondrial intermembrane space. Once in the cytosol, these factors act as (or activate) catabolic hydrolases that digest of the cell's content, thus causing cell death and facilitating the subsequent corpse removal. Multiple lethal signal transduction molecules, toxins and experimental anticancer agents can induce mitochondrial membrane permeabilization, a property that is taken advantage for tumour therapy. Conversely, some pharmacological agents have been designed to inhibit mitochondrial membrane permeabilization and can be used for the experimental avoidance of unwarranted cell death, for instance in stroke or myocardial infarction. Altogether, it appears that mitochondrial cell death control has wide physiological, pathological and pharmacological implications.

These past years, we focused our researches on the identification of novel, potential peptide targets for cancer immunotherapy. Amongst the peptides we identified, two are composed of fragments originally distant in the parental protein and are produced by a novel mechanism termed peptide splicing. The peptide splicing reaction takes place in the proteasome and occurs by transpeptidation. Here, we describe the discovery of this new mechanism of production of antigenic peptides.

The function of glandular organs (mammary and salivary glands, exocrine pancreas) depends on their branched tubular epithelial architecture. During pancreas and salivary glands development, we have shown the succession of two opposite epithelial transitions (monolayer --> mass --> tubulo-glandular monolayers). These transitions are controlled by paracrine interactions via mesenchymal cells (SDF-1) and endothelial cells (VEGF), and coordinated by transcriptional networks. The transcription factor HNF-6 is indispensable for tube formation; ZONAB is an actor of the proliferation/differentiation switch, highly expressed in the proliferating epithelial mass. Understanding the mechanisms that control branched glandular differentiation is important for developmental biology and could shed light on polykystic diseases and in situ carcinomas.

Peritoneal dialysis involves diffusive and convective transports and osmosis through the highly vascularized peritoneal membrane. Several lines of evidence have demonstrated that the water channel aquaporin-1 (AQP1) corresponds to the ultrasmall pore predicted by the modelization of peritoneal transport. Proof-of-principle studies have shown that upregulation of the expression of AQP1 in peritoneal capillaries is reflected by increased water permeability and ultrafiltration, without affecting the osmotic gradient and the permeability for small solutes. Inversely, studies in Aqp1 mice have shown that haplo-insufficiency in AQP1 is reflected by significant attenuation of water transport. Recent studies have identified lead compounds that could act as agonists of aquaporins, as well as putative binding sites and potential mechanisms of gating the water channel. By modulating water transport, these pharmacological agents could have clinically relevant effects in targeting specific tissues or disease states. These studies on the peritoneal membrane also provide an experimental framework to investigate the role of water channels in the endothelium and various cell types.

The Escherichia coli periplasm contains several proteins from the thioredoxin family. DsbA and Dsbc interact with unfolded proteins to catalyze disulfide bond formation or isomerisation, respectively. The function of a third protein, DsbG, had remained elusive. By trapping DsbG attached to three of its substrates, we made the intriguing discovery that DsbG interacts with folded proteins possessing only one cysteine residue in their sequence. This residue is vulnerable to oxidation and forms a sulfenic acid in vitro. We sought to determine whether this cysteine is also sulfenylated in vivo, which led us to observe extensive sulfenic acid formation in the periplasm, especially in dsbcdsbG strains. Thus, by chasing the substrates of DsbG, we uncovered a new reducing system that is involved in sulfenic acid reduction on a global level (Depuydt et al., Science 326 (2009), 1109-1111). DsbG appears to be a key player in that system. Our work reveals one potentially widespread mechanism whereby the very reactive sulfenic acid modification can be controlled in the cellular environment.

The skin is a complex organ composed by two essential components, the epidermis and the dermis. It is developed to protect the organism against all external damage e.g. infectious agents, uv and contains a number of different specialized cell types with distinct functions. The skin is also built up by extracellular matrix constituents, which are either arranged into basement membrane structures or form the interstitial connective tissue. There is extensive communication between and within the cellular compartments and the extracellular matrix at different levels to establish, maintain and restore skin homeostasis. It is the aim of our group to understand the mechanisms, how these different cellular and structural components communicate and to dissect the molecular basis of diseases resulting from disturbances of this balance. These include chronic inflammatory diseases, fibrosis and defective regulation of wound healing. This will allow the identification of new therapeutic targets that can be used to specifically interfere with defined steps leading to these diseases.

The fundamental role of the thyroid gland is to ensure the biosynthesis of thyroid hormones whose primary role during embryonic development and the maintenance of homeostasis after birth is well known. The challenge here is double, as the hormone synthesis depends on both potentially toxic biochemical processes, as long as they are not fully contained, and the availability of a trace element, iodine, whose uptake may be extremely variable depending on the geographical location and the physiological status of individuals. The squaring of the circle has been resolved by the thyroid gland during its phylogenetic maturation by setting up angiofollicular units, morphological entities whose the perfect functional coherence between the different compartments within them (epithelial, endothelial and interstitial) results from a high level three-dimensional assemblage. This morphological and functional integration warrants adequate supplies of thyroid hormones whose mobilization must be triggered at any time when necessary. This functional requirement finds its expression in the morphological heterogeneity that ultimately culminates in the formation of nodules. Each angiofollicular unit is an individualized entity with its own genotypic and phenotypic asset that runs on the extrinsic control of TSH and a host of autocrine and paracrine factors. But subtle intrinsic mechanisms of self-regulation, operating out of any outside influences, constantly adjust the availability of players involved in the hormonal synthesis (iodine, thyroglobulin) within a biochemical entity (the thyroxisome) that is perfectly suited for this synthesis taking place without prejudice to the thyrocyte. The hormonal synthesis generates oxygen-derived substances as oxidative load or stress, though perfectly controlled in healthy thyrocytes. Any injury related to the nature, the amount, or where in the cell oxygen-derived substances are produced, may lead to morphological and functional breakdowns responsible for various disease processes, including those of autoimmune or even neoplastic nature.

Bone tissue is a marvellous material. Basic bone function is to be structurally stiff and strong. Stiffness allows vertebrates to maintain their shape, to protect the organs and to move. Being strong, bone only breaks in exceptional circumstances. Osteoporosis is a disease where fractures happen too often, because of abnormal bone fragility. In this situation, bone--especially cancellous bone--does not take up its first duty. Trabeculae are scarce and thin, leading to very low tissue density. Biomechanical tests and clinical evidence have shown that some subjects have, with equal bone density, stronger or weaker bone tissue. This led to the concept of bone quality. Even if other hypotheses have been systematically explored, it seems that bone collagen chemical nature, especially its cross-link profile, significantly influences human bone quality.