Hans A. Büller

Gastrointestinal expression and partial cDNA cloning of murine Muc2

To help us investigate the role of mucin in the protection of the colonic epithelium in the mouse, we aimed to identify the murine colonic mucin (MCM) and its encoding gene. We isolated MCM, raised an anti-MCM antiserum, and studied the biosynthesis of MCM in the gastrointestinal tract. Isolated MCM resembled other mucins in physicochemical properties. Anti-MCM recognized MCM as well as rat and human MUC2 on Western blots, interacting primarily with peptide epitopes, indicating that MCM was identical to murine Muc2. Using anti-MCM and previously characterized anti-human and anti-rat MUC2 antibodies, we identified a murine Muc2 precursor in the colon of approximately 600 kDa, which appeared similar in size to rat and human MUC2 precursors. Western blotting, immunoprecipitation of metabolically labeled mucins, and immunohistochemistry showed that murine Muc2 was expressed in the colon and the small intestine but was absent in the stomach. To independently identify murine Muc2, we cloned a cDNA fragment from murine colonic mRNA, encoding the 302 NH2-terminal amino acids of murine Muc2. The NH2 terminus of murine Muc2 showed 86 and 75% identity to the corresponding rat and human MUC2 peptide sequences, respectively. Northern blotting with a murine Muc2 cDNA probe showed hybridization to a very large mRNA, which was expressed highly in the colon and to some extend in the small intestine but was absent in the stomach. In situ hybridization showed that the murine Muc2 mRNA was confined to intestinal goblet cells. In conclusion, by two independent sets of experiments we identified murine Muc2, which appears homologous to rat and human MUC2. Because Muc2 is prominently expressed in the colon, it is most likely to be the predominant mucin in the colonic mucus layer.To help us investigate the role of mucin in the protection of the colonic epithelium in the mouse, we aimed to identify the murine colonic mucin (MCM) and its encoding gene. We isolated MCM, raised an anti-MCM antiserum, and studied the biosynthesis of MCM in the gastrointestinal tract. Isolated MCM resembled other mucins in physicochemical properties. Anti-MCM recognized MCM as well as rat and human MUC2 on Western blots, interacting primarily with peptide epitopes, indicating that MCM was identical to murine Muc2. Using anti-MCM and previously characterized anti-human and anti-rat MUC2 antibodies, we identified a murine Muc2 precursor in the colon of ∼600 kDa, which appeared similar in size to rat and human MUC2 precursors. Western blotting, immunoprecipitation of metabolically labeled mucins, and immunohistochemistry showed that murine Muc2 was expressed in the colon and the small intestine but was absent in the stomach. To independently identify murine Muc2, we cloned a cDNA fragment from murine colonic mRNA, encoding the 302 NH2-terminal amino acids of murine Muc2. The NH2 terminus of murine Muc2 showed 86 and 75% identity to the corresponding rat and human MUC2 peptide sequences, respectively. Northern blotting with a murine Muc2 cDNA probe showed hybridization to a very large mRNA, which was expressed highly in the colon and to some extend in the small intestine but was absent in the stomach. In situ hybridization showed that the murine Muc2 mRNA was confined to intestinal goblet cells. In conclusion, by two independent sets of experiments we identified murine Muc2, which appears homologous to rat and human MUC2. Because Muc2 is prominently expressed in the colon, it is most likely to be the predominant mucin in the colonic mucus layer.

Sulphation and secretion of the predominant secretory human colonic mucin MUC2 in ulcerative colitis

BACKGROUND Decreased synthesis of the predominant secretory human colonic mucin (MUC2) occurs during active ulcerative colitis. AIMS To study possible alterations in mucin sulphation and mucin secretion, which could be the cause of decreased mucosal protection in ulcerative colitis. METHODS Colonic biopsy specimens from patients with active ulcerative colitis, ulcerative colitis in remission, and controls were metabolically labelled with [35S]-amino acids or [35S]-sulphate, chase incubated and analysed by SDS-PAGE, followed by quantitation of mature [35S]-labelled MUC2. For quantitation of total MUC2, which includes non-radiolabelled and radiolabelled MUC2, dot blotting was performed, using a MUC2 monoclonal antibody. RESULTS Between patient groups, no significant differences were found in [35S]-sulphate content of secreted MUC2 or in the secreted percentage of either [35S]-amino acid labelled MUC2 or total MUC2. During active ulcerative colitis, secretion of [35S]-sulphate labelled MUC2 was significantly increased twofold, whereas [35S]-sulphate incorporation into MUC2 was significantly reduced to half. CONCLUSIONS During active ulcerative colitis, less MUC2 is secreted, because MUC2 synthesis is decreased while the secreted percentage of MUC2 is unaltered. Furthermore, sulphate content of secreted MUC2 is unaltered by a specific compensatory mechanism, because sulphated MUC2 is preferentially secreted while sulphate incorporation into MUC2 is reduced.

Epithelial proliferation, cell death, and gene expression in experimental colitis: alterations in carbonic anhydrase I, mucin MUC2, and trefoil factor 3 expression

AbstractAbstractn Background and aims. To gain insight in intestinal epithelial proliferation, cell death, and gene expression during experimental colitis rats were treated with dextran sulfate sodium (DSS) for 7xa0days.n Materials and methods. Proximal and distal colonic segments were excised on days 2, 5, 7, and 28. Epithelial proliferation, cell death, enterocyte gene expression (carbonic anhydrase I (CAxa0I) and goblet cell gene expression (mucin, MUC2; trefoil factor 3, TFF3) were studied immunohistochemically and biochemically.n Results. Proliferative activity was decreased in the proximal and distal colon at the onset of disease (day 2). However, during active disease (days 5–7) epithelial proliferation was increased in the entire proximal colon and in the proximity of ulcerations in the distal colon. During DSS treatment the number of apoptotic cells in the epithelium of both colonic segments was increased. In the entire colon surface enterocytes became flattened and CAxa0I negative during active disease (day 5–7). Additionally, CAxa0I levels in the distal colon significantly decreased during this phase. In contrast, during the regenerative phase (day 28) CAxa0I levels were restored in the distal colon and up-regulated in the proximal colon. During all disease phases increased numbers of goblet cells were observed in the surface epithelium of the entire colon. In the distal colon TFF3 expression extended to the bottom of the crypts during active disease. Finally, MUC2 and TFF3 expression was increased in the proximal colon during disease.n Conclusion. DSS affected the epithelium by inhibiting proliferation and inducing apoptosis. DSS-induced inhibition of CAxa0I expression indicates down-regulation of specific enterocyte functions. Accumulation of goblet cells in the surface epithelium and up-regulation of MUC2 and TFF3 expression in the proximal colon underline the importance of goblet cells in epithelial protection and repair, respectively.

Translation of rare disease research into orphan drug development: disease matters

More than 25 years of orphan drug regulations have yielded several new treatments for patients with rare diseases. Here, we show that successful translation of rare disease research into an orphan drug discovery and development programme is dependent on the disease class, its prevalence and the disease-specific scientific output. Our findings indicate that current orphan drug legislation alone is not sufficient to stimulate orphan drug development for diseases with a very low prevalence. Consequently, additional incentives should focus on stimulating the specific needs of rare disease research at disease class level.

Interleukin 10-Deficient Mice Exhibit Defective Colonic Muc2 Synthesis Before and After Induction of Colitis by Commensal Bacteria

Germ-free (GF) interleukin 10-deficient (IL-10−/−) mice develop chronic colitis after colonization by normal enteric bacteria. Muc2 is the major structural component of the protective colonic mucus. Our aim was to determine whether primary or induced aberrations in Muc2 synthesis occur in GF IL-10−/− mice that develop colitis after bacterial colonization. GF IL-10−/− and wild-type mice were colonized with commensal bacteria for various intervals up to 6 weeks. Colitis was quantified by histologic score and IL-12 secretion. Muc2 synthesis, total level of Muc2, and Muc2 sulfation were measured quantitatively. GF IL-10−/− mice showed 10-fold lower Muc2 synthesis and Muc2 levels compared with GF wild-type mice, but Muc2 sulfation was not different. When bacteria were introduced, IL-10−/− mice developed colitis, whereas wild-type mice remained healthy. Muc2 synthesis was unchanged in wild-type mice, but IL-10−/− mice showed a peak increase in Muc2 synthesis 1 week after bacterial introduction, returning to baseline levels after 2 weeks. Total Muc2 levels decreased 2-fold in wild-type mice but remained at stable low levels in IL-10−/− mice. Upon introducing bacteria, Muc2 sulfation increased 2-fold in wild-type mice, whereas in IL-10−/− mice Muc2 sulfation decreased 10-fold. In conclusion, a primary defect in colonic Muc2 synthesis is present in IL-10−/− mice, whereas bacterial colonization and colitis in these mice led to reduced Muc2 sulfation. These quantitative and structural aberrations in Muc2 in IL-10−/− mice likely reduce the ability of their mucosa to cope with nonpathogenic commensal bacteria and may contribute to their susceptibility to develop colitis.

Predictors of orphan drug approval in the European Union

ObjectiveTo encourage the development of drugs for rare diseases, orphan drug legislation has been introduced in the USA (1983) and in the EU (2000). Recent literature discusses factors that may influence the development of new orphan medicinal products in the EU. This study aims to identify predictors for successful marketing authorisation of potential orphan drugs in the EU.MethodsA comparison between randomly selected authorised and a matched sample of not-yet-authorised orphan drug designations has been performed. Determinants in the study included characteristics of the indication, of the product and of the sponsor. Data were collected from the public domain only.ResultsOrphan drug approval was strongly associated with previous experience of the sponsor in obtaining approval for another orphan drug (ORu2009=u200917.3, 95% CIu2009=u20095.6–53.1). Furthermore, existing synthetic entities compared to biotechnology products tended to have a higher likelihood of reaching approval status (ORu2009=u20093.9, 95% CIu2009=u20090.9–16.6).ConclusionThis study showed that experience of a company in developing orphan drugs is an important predictor for subsequent authorisation of other orphan drugs. The same applies for existing (synthetic) molecules, for which much knowledge is available. Further research should be directed towards studying the quality of the clinical development program of those designated orphan medicinal products not reaching approval status.

Transcriptional activation of the murine Muc5ac mucin gene in epithelial cancer cells by TGF-beta/Smad4 signalling pathway is potentiated by Sp1.

The nucleotide sequence of the pMS1 clone was submitted to the GenBank Nucleotide Sequence Database under accession number AF288076. Changes in the expression of mucin genes in gastrointestinal cancers is thought to contribute to the development of the disease. In our laboratory we have shown previously that MUC5AC is aberrantly expressed in rectosigmoid villous adenomas. However, the regulatory mechanisms underlying that altered profile of expression is unknown. In order to study its regulation at the transcriptional level, we have isolated and characterized 5.5 kb of the 5-flanking region of the mouse Muc5ac mucin gene. The promoter is flanked by a TATA box and a transcriptional start site is located 22 bp downstream of the TATA box. Analysis of the sequence showed a high density of binding sites for Smad4, an essential factor in the signalling cascade activated by TGF-beta (transforming growth factor-beta), and Sp1, an important factor in the regulation of MUC5AC. This led us to study Muc5ac regulation by TGF-beta. We show that exogenous addition of TGF-beta to the cells induces Muc5ac endogenous expression, promoter activity and Smad4 binding to the promoter. By co-transfection studies we show that Smad4 is essential for Muc5ac promoter activation and that it does not synergize with Smad2 or Smad3. By gel-retardation and co-transfection assays, we identified Sp1 and Sp3 as important regulators of Muc5ac expression and showed that Smad4 and Sp1 act in a co-operative manner to transactivate Muc5ac promoter activity. Altogether these results bring new insights into the molecular mechanisms of TGF-beta-mediated up-regulation of Muc5ac and enhance our understanding as to how Muc5ac is regulated in certain pathologies of the gastrointestinal tract.

Lactose and fructose malabsorption in children with recurrent abdominal pain: results of double-blinded testing

Aim:u2002 To investigate malabsorption of lactose and fructose as causes of recurrent abdominal pain (RAP).

Recurrent abdominal pain in 200 children: Somatic causes and diagnostic criteria

Aim:u2002 To establish to what extent somatic causes can be found in children referred to secondary care with recurrent abdominal pain.

Clinical and laboratory findings in 220 children with recurrent abdominal pain.

Aim:u2002 To investigate the clinical and laboratory findings in children with recurrent abdominal pain (RAP).