Diffuse alveolar haemorrhage (DAH) is a catastrophic pulmonary complication of systemic lupus erythematosus. It can result in refractory hypoxaemia despite mechanical ventilation. Increasing lung compliance and worsening pulmonary hypertension can potentiate cardiogenic shock from acute right ventricular failure. In such patients with cardiopulmonary collapse, veno-arterial (V-A) ECMO maybe a viable option that can provide the required haemodynamic support. However, the use of V-A ECMO in such patients is limited due to an associated increased risk of bleeding. Our case report describes the successful use of V-A ECMO without the use of systemic anticoagulation in a patient with DAH. Despite the absence of systemic anticoagulation, no thrombotic complications within the circuit were noted.

Lymphangioleiomyomatosis (LAM) is a rare cystic lung disease, commonly affecting women in the reproductive age group. Exacerbation of pre-existing disease is common during pregnancy likely due to the up-regulation of estrogen and progesterone receptors present within the proliferating smooth muscle cells. This case highlights a dramatic presentation of LAM for the first time in pregnancy, its rapid progression during gestation, and a partial resolution with delivery. The unusual radiographic imaging in this patient, lacked the characteristic cystic lesions commonly associated with LAM, but instead demonstrated a dense interstitial pattern with micronodular expansion of the interlobular septa suggesting severe lymphatic obstruction.

Clathrin, a cytosolic protein composed of heavy and light chain subunits, assembles into a vesicle coat, controlling receptor-mediated endocytosis. To establish clathrin light chain (CLC) function in vivo, we engineered mice lacking CLCa, the major CLC isoform in B lymphocytes, generating animals with CLC-deficient B cells. In CLCa-null mice, the germinal centers have fewer B cells, and they are enriched for IgA-producing cells. This enhanced switch to IgA production in the absence of CLCa was attributable to increased transforming growth factor β receptor 2 (TGFβR2) signaling resulting from defective endocytosis. Internalization of C-X-C chemokine receptor 4 (CXCR4), but not CXCR5, was affected in CLCa-null B cells, and CLC depletion from cell lines affected endocytosis of the δ-opioid receptor, but not the β2-adrenergic receptor, defining a role for CLCs in the uptake of a subset of signaling receptors. This instance of clathrin subunit deletion in vertebrates demonstrates that CLCs contribute to clathrin's role in vivo by influencing cargo selectivity, a function previously assigned exclusively to adaptor molecules.

The clathrin light chain (CLC) subunits participate in several membrane traffic pathways involving both clathrin and actin, through binding the actin-organizing huntingtin-interacting proteins (Hip). However, CLCs are dispensable for clathrin-mediated endocytosis of many cargoes. Here we observe that CLC depletion affects cell migration through Hip binding and reduces surface expression of β1-integrin by interference with recycling following normal endocytosis of inactive β1-integrin. CLC depletion and expression of a modified CLC also inhibit the appearance of gyrating (G)-clathrin structures, known mediators of rapid recycling of transferrin receptor from endosomes. Expression of the modified CLC reduces β1-integrin and transferrin receptor recycling, as well as cell migration, implicating G-clathrin in these processes. Supporting a physiological role for CLC in migration, the CLCb isoform of CLC is upregulated in migratory human trophoblast cells during uterine invasion. Together, these studies establish CLCs as mediating clathrin–actin interactions needed for recycling by G-clathrin during migration. Clathrin light chain (CLC) subunits are dispensable for clathrin-mediated endocytosis of a number of cargoes. Majeed et al. report that CLCs are however required for gyrating-clathrin-dependent recycling of inactive β1-integrins, the absence of which impairs cell migration.

Clathrin depletion by ribonucleic acid interference (RNAi) impairs mitotic spindle stability and cytokinesis. Depletion of several clathrin-associated proteins affects centrosome integrity, suggesting a further cell cycle function for clathrin. In this paper, we report that RNAi depletion of CHC17 (clathrin heavy chain 17) clathrin, but not the CHC22 clathrin isoform, induced centrosome amplification and multi-polar spindles. To stage clathrin function within the cell cycle, a cell line expressing SNAP-tagged clathrin light chains was generated. Acute clathrin inactivation by chemical dimerization of the SNAP-tag during S phase caused reduction of both clathrin and ch-TOG (colonic, hepatic tumor overexpressed gene) at metaphase centrosomes, which became fragmented. This was pheno-copied by treatment with Aurora A kinase inhibitor, suggesting a centrosomal role for the Aurora A-dependent complex of clathrin, ch-TOG, and TACC3 (transforming acidic coiled-coil protein 3). Clathrin inactivation in S phase also reduced total cellular levels of ch-TOG by metaphase. Live-cell imaging showed dynamic clathrin recruitment during centrosome maturation. Therefore, we propose that clathrin promotes centrosome maturation by stabilizing the microtubule-binding protein ch-TOG, defining a novel role for the clathrin-ch-TOG-TACC3 complex.

BACKGROUND:Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant disease with a varying range of phenotypes involving abnormal vasculature primarily manifested as arteriovenous malformations in various organs, including the nose, brain, liver, and lungs. The varied presentation and involvement of different organ systems makes the choice of potential treatment medications difficult.RESULTS:A patient with a mixed-clinical presentation and presumed diagnosis of HHT, severe exertional dyspnea, and diffuse pulmonary shunting at the microscopic level presented for treatment. We sought to analyze her metabolomic plasma profile to assist with pharmacologic treatment selection. Fasting serum samples from 5 individuals (4 healthy and 1 with HHT) were metabolomically profiled. A global metabolic network reconstruction, Recon 1, was used to help guide the choice of medication via analysis of the differential metabolism between the patient and healthy controls using metabolomic data. Flux Balance Analysis highlighted changes in metabolic pathway activity, notably in nitric oxide synthase (NOS), which suggested a potential link between changes in vascular endothelial function and metabolism. This finding supported the use of an already approved medication, bevacizumab (Avastin). Following 2 months of treatment, the patient's metabolic profile shifted, becoming more similar to the control subject profiles, suggesting that the treatment was addressing at least part of the pathophysiological state.CONCLUSIONS:In this 'individualized case study' of personalized medicine, we carry out untargeted metabolomic profiling of a patient and healthy controls. Rather than filtering the data down to a single value, these data are analyzed in the context of a network model of metabolism, in order to simulate the biochemical phenotypic differences between healthy and disease states; the results then guide the therapy. This presents one approach to achieving the goals of individualized medicine through Systems Biology and causal models analysis.

The Hedgehog family of secreted morphogens specifies the fate of a large number of different cell types within invertebrate and vertebrate embryos, including the muscle cell precursors of the embryonic myotome of zebrafish. Formation of Hedgehog-sensitive muscle fates is disrupted within homozygous zebrafish mutants of the "you"-type class, the majority of which disrupt components of the Hedgehog (HH) signal transduction pathway. We have undertaken a phenotypic and molecular characterisation of one of these mutants, you, which we show results from mutations within the zebrafish orthologue of the mammalian gene scube2. This gene encodes a member of the Scube family of proteins, which is characterised by several protein motifs including EGF and CUB domains. Epistatic and molecular analyses position Scube2 function upstream of Smoothened (Smoh), the signalling component of the HH receptor complex, suggesting that Scube2 may act during HH signal transduction prior to, or during, receipt of the HH signal at the plasma membrane. In support of this model we show that scube2 has homology to cubilin, which encodes an endocytic receptor involved in protein trafficking suggesting a possible mode of function for Scube2 during HH signal transduction.

The spatial organization of organelles within a cell is dependent on microtubules. Recently, members of the Hook family of proteins have been proposed to function in linking organelles to microtubules. We report the identification of a completely novel protein family, the Hook‐related protein (HkRP) family, from which the Hook proteins have diverged. Bioinformatic analysis of the HkRP family revealed several conserved domains, including a unique C‐terminal HkRP domain. The central region of each protein is comprised of an extensive coiled‐coil domain, and the N‐terminus contains a putative microtubule‐binding domain. This domain has been shown to bind microtubules in the Hook protein and show that the HkRP1 protein is microtubule‐associated. While endogenous HkRP1 has no distinct organelle association, expression of the C‐terminal membrane‐binding domain suggests a function of the HkRP1 in early endosome. Ultrastructural studies reveal that expression of the C‐terminal HkRP1 domain causes an accumulation of internal membranes with an electron‐dense coat. Co‐localization studies show a concomitant redistribution of the early endosome marker sorting‐nexin 1 but not the early endosome antigen‐1 (EEA1). The steady‐state distribution of the epidermal growth factor receptor is also specifically disrupted by expression of the C‐terminal domain. We propose that HkRP1 is involved in the process of tubulation of sorting nexin‐1 positive membranes from early endosome subdomains.

The hedgehog signaling pathway is indispensable in embryogenesis, being responsible for the development of a wide array of vertebrate organs. Given its importance in embryogenesis, the precise regulation of hedgehog signaling is crucial. Aberrant activation of this pathway in postnatal life has been associated with a number of tumor types, reinforcing the role of developmental signaling pathways in tumorigenesis. The small GTPase Rab23 acts as a negative regulator of the hedgehog signaling pathway, most notably in the vertebrate neural system. By analogy with studies of other Rab proteins, analysis of the localization of wild-type and constitutively active and inactive forms of Rab23 provides the potential to shed light on the role of Rab23 at the cellular level. We previously produced expression constructs encoding these proteins for analysis in mammalian cell cultures at both the light and the electron microscopy level. This revealed that both wild-type and active Rab23 localizes to the plasma membrane and to endocytic vesicles (T. M. Evans et al. [2003] Traffic4, 869-884). We describe the methods used to design and make the Rab23 expression constructs, and to assess their localization relative to key hedgehog pathways and endocytic markers in both transiently and stably transfected cell cultures.

The regulation of hedgehog signaling by vesicular trafficking was exemplified by the finding that Rab23, a Rab‐GTPase vesicular transport protein, is mutated in open brain mice. In this study, the localization of Rab23 was analyzed by light and immunoelectron microscopy after expression of wild‐type (Rab23‐GFP), constitutively active Rab23 (Rab23Q68L‐GFP), and inactive Rab23 (Rab23S23N‐GFP) in a range of mammalian cell types. Rab23‐GFP and Rab23Q68L‐GFP were predominantly localized to the plasma membrane but were also associated with intracellular vesicular structures, whereas Rab23S23N‐GFP was predominantly cytosolic. Vesicular Rab23‐GFP colocalized with Rab5Q79L and internalized transferrin‐biotin, but not with a marker of the late endosome or the Golgi complex. To investigate Rab23 with respect to members of the hedgehog signaling pathway, Rab23‐GFP was coexpressed with either patched or smoothened. Patched colocalized with intracellular Rab23‐GFP but smoothened did not. Analysis of patched distribution by light and immunoelectron microscopy revealed it is primarily localized to endosomal elements, including transferrin receptor‐positive early endosomes and putative endosome carrier vesicles and, to a lesser extent, with LBPA‐positive late endosomes, but was excluded from the plasma membrane. Neither patched or smoothened distribution was altered in the presence of wild‐type nor mutant Rab23‐GFP, suggesting that despite the endosomal colocalization of Rab23 and patched, it is likely that Rab23 acts more distally in regulating hedgehog signaling.

American Journal of Medical GeneticsVolume 103, Issue 4 p. 344-347 Letter to the Editor Novel mutation in the Δ7-dehydrocholesterol reductase gene in an Australian patient with Smith-Lemli-Opitz syndrome Timothy Evans, Timothy Evans Institute for Molecular Bioscience, University of Queensland, St Lucia, Australia Cooperative Research Centre for the Discovery of Genes for Common Human Diseases, Cerylid, Richmond, AustraliaSearch for more papers by this authorAlisa Poh, Alisa Poh Institute for Molecular Bioscience, University of Queensland, St Lucia, Australia Cooperative Research Centre for the Discovery of Genes for Common Human Diseases, Cerylid, Richmond, AustraliaSearch for more papers by this authorCharlotte Webb, Charlotte Webb Institute for Molecular Bioscience, University of Queensland, St Lucia, Australia Cooperative Research Centre for the Discovery of Genes for Common Human Diseases, Cerylid, Richmond, AustraliaSearch for more papers by this authorBrandon Wainwright, Brandon Wainwright Institute for Molecular Bioscience, University of Queensland, St Lucia, Australia Cooperative Research Centre for the Discovery of Genes for Common Human Diseases, Cerylid, Richmond, AustraliaSearch for more papers by this authorCarol Wicking, Corresponding Author Carol Wicking [email protected] Institute for Molecular Bioscience, University of Queensland, St Lucia, Australia Cooperative Research Centre for the Discovery of Genes for Common Human Diseases, Cerylid, Richmond, AustraliaInstitute for Molecular Bioscience, The University of Queensland, St Lucia 4072 Queensland, Australia.Search for more papers by this authorIan Glass, Ian Glass Queensland Clinical Genetics Service, Herston, Brisbane, AustraliaSearch for more papers by this authorWilliam F. Carey, William F. Carey Department of Chemical Pathology, Women's and Children's Hospital, Adelaide, AustraliaSearch for more papers by this authorMichael Fietz, Michael Fietz Department of Chemical Pathology, Women's and Children's Hospital, Adelaide, AustraliaSearch for more papers by this author Timothy Evans, Timothy Evans Institute for Molecular Bioscience, University of Queensland, St Lucia, Australia Cooperative Research Centre for the Discovery of Genes for Common Human Diseases, Cerylid, Richmond, AustraliaSearch for more papers by this authorAlisa Poh, Alisa Poh Institute for Molecular Bioscience, University of Queensland, St Lucia, Australia Cooperative Research Centre for the Discovery of Genes for Common Human Diseases, Cerylid, Richmond, AustraliaSearch for more papers by this authorCharlotte Webb, Charlotte Webb Institute for Molecular Bioscience, University of Queensland, St Lucia, Australia Cooperative Research Centre for the Discovery of Genes for Common Human Diseases, Cerylid, Richmond, AustraliaSearch for more papers by this authorBrandon Wainwright, Brandon Wainwright Institute for Molecular Bioscience, University of Queensland, St Lucia, Australia Cooperative Research Centre for the Discovery of Genes for Common Human Diseases, Cerylid, Richmond, AustraliaSearch for more papers by this authorCarol Wicking, Corresponding Author Carol Wicking [email protected] Institute for Molecular Bioscience, University of Queensland, St Lucia, Australia Cooperative Research Centre for the Discovery of Genes for Common Human Diseases, Cerylid, Richmond, AustraliaInstitute for Molecular Bioscience, The University of Queensland, St Lucia 4072 Queensland, Australia.Search for more papers by this authorIan Glass, Ian Glass Queensland Clinical Genetics Service, Herston, Brisbane, AustraliaSearch for more papers by this authorWilliam F. Carey, William F. Carey Department of Chemical Pathology, Women's and Children's Hospital, Adelaide, AustraliaSearch for more papers by this authorMichael Fietz, Michael Fietz Department of Chemical Pathology, Women's and Children's Hospital, Adelaide, AustraliaSearch for more papers by this author First published: 13 September 2001 https://doi.org/10.1002/ajmg.1573Citations: 7Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat REFERENCES Carstea ED, Morris JA, Coleman KG, Loftus SK, Zhang D, Cummings C, Gu J, Rosenfeld MA, Pavan WJ, Krizman DB, Nagle J, Polymeropoulos MH, Sturley SL, Ioannou YA, Higgins ME, Comly M, Cooney A, Brown A, Kaneski CR, Blanchette-Mackie EJ, Dwyer NK, Neufeld EB, Chang TY, Liscum L, Strauss JF, Ohno K, Zeigler M, Carmi R, Sokol J, Markie D, O'Neill RR, van Diggelen OP, Elleder M, Patterson MC, Brady RO, Vanier MT, Pentehey PG. 1997. Niemann-Pick C1 disease gene: homology to mediators of cholesterol homeostasis. Science 277: 228–231. 10.1126/science.277.5323.228 CASPubMedWeb of Science®Google Scholar Chiang C, Litingtung Y, Lee E, Young KE, Corden JL, Westphal H, Beachy PA. 1996. Cyclopia and defective axial patterning in mice lacking sonic hedgehog gene function. Nature 383: 407–413. 10.1038/383407a0 CASPubMedWeb of Science®Google Scholar Craig JE, Savage V, Cowley D, Clague A, Glass IA. 1999. Low maternal serum oestriol at mid-trimester may indicate a fetal disorder of cholesterol biosynthesis. Aust N Z J Obstet Gynaecol 39: 249–251. 10.1111/j.1479-828X.1999.tb03384.x CASPubMedWeb of Science®Google Scholar Fitzky BU, Witsch-Baumgartner M, Erdel M, Lee JN, Paik YK, Glossmann H, Utermann G, Moebius FF. 1998. Mutations in the δ7-sterol reductase gene in patients with the Smith-Lemli-Opitz syndrome. Proc Natl Acad Sci USA 95: 8181–8186. 10.1073/pnas.95.14.8181 CASPubMedWeb of Science®Google Scholar Fitzky BU, Glossmann H, Utermann G, Moebius FF. 1999. Molecular genetics of the Smith-Lemli-Opitz syndrome and postsqualene sterol metabolism. Curr Opin Lipidol 10: 123–131. 10.1097/00041433-199904000-00006 CASPubMedWeb of Science®Google Scholar Kelley RI, Hennekam RC. 2000. The Smith-Lemli-Opitz syndrome. J Med Genet 37: 321–335. 10.1136/jmg.37.5.321 CASPubMedWeb of Science®Google Scholar Kelley RL, Roessler E, Hennekam RC, Feldman GL, Kosaki K, Jones MC, Palumbos JC, Muenke M. 1996. Holoprosencephaly in RSH/Smith-Lemli-Opitz syndrome: does abnormal cholesterol metabolism affect the function of sonic hedgehog? Am J Med Genet 66: 478–484. 10.1002/(SICI)1096-8628(19961230)66:4<478::AID-AJMG22>3.0.CO;2-Q CASPubMedWeb of Science®Google Scholar Kolf-Clauw M, Chevy F, Siliart B, Wolf C, Mulliez N, Roux C. 1997. Cholesterol biosynthesis inhibited by BM15.766 induces holoprosencephaly in the rat. Teratology 56: 188–200. 10.1002/(SICI)1096-9926(199709)56:3<188::AID-TERA2>3.0.CO;2-Y CASPubMedWeb of Science®Google Scholar Lanoue L, Dehart DB, Hinsdale ME, Maeda N, Tint GS, Sulik KK. 1997. Limb, genital, CNS, and facial malformations result from gene/environment-induced cholesterol deficiency: further evidence for a link to sonic hedgehog. Am J Med Genet 73: 24–31. 10.1002/(SICI)1096-8628(19971128)73:1<24::AID-AJMG6>3.0.CO;2-P CASPubMedWeb of Science®Google Scholar Loftus SK, Morris JA, Carstea ED, Gu JZ, Cummings C, Brown A, Ellison J, Ohno K, Rosenfeld MA, Tagle DA, Pentchev PG, Pavan WJ. 1997. Murine model of Niemann-Pick C disease: mutation in a cholesterol homeostasis gene. Science 277: 232–235. 10.1126/science.277.5323.232 CASPubMedWeb of Science®Google Scholar Moebius FF, Fitzky BU, Lee JN, Paik YK, Glossmann H. 1998. Molecular cloning and expression of the human δ7-sterol reductase. Proc Natl Acad Sci USA 95: 1899–1902. 10.1073/pnas.95.4.1899 CASPubMedWeb of Science®Google Scholar Porter JA, Young KE, Beachy PA. 1996. Cholesterol modification of hedgehog signaling proteins in animal development. Science 274: 255–259. 10.1126/science.274.5285.255 CASPubMedWeb of Science®Google Scholar Repetto M, Maziere JC, Citadelle D, Dupuis R, Meier M, Biade S, Quiec D, Roux C. 1990. Teratogenic effect of the cholesterol synthesis inhibitor AY 9944 on rat embryos in vitro. Teratology 42: 611–618. 10.1002/tera.1420420605 CASPubMedWeb of Science®Google Scholar Roessler E, Belloni E, Gaudenz K, Jay P, Berta P, Scherer SW, Tsui LC, Muenke M. 1996. Mutations in the human sonic hedgehog gene cause holoprosencephaly. Nat Genet 14: 357–360. 10.1038/ng1196-357 CASPubMedWeb of Science®Google Scholar Roux C, Aubry M. 1966. Teratogenic action in the rat of an inhibitor of cholesterol synthesis, AY 9944. C R Seances Soc Biol Fil 160: 1353–1357. CASPubMedWeb of Science®Google Scholar Roux C, Wolf C, Mulliez N, Gaoua W, Cormier V, Chevy F, Citadelle D. 2000. Role of cholesterol in embryonic development. Am J Clin Nutr 71 ( Suppl): 1270s–1279s. CASPubMedWeb of Science®Google Scholar Wassif CA, Maslen C, Kachilele-Linjewile S, Lin D, Linck LM, Connor WE, Steiner RD, Porter FD. 1998. Mutations in the human sterol δ7-reductase gene at 11q12-13 cause Smith-Lemli-Opitz syndrome. Am J Hum Genet 63: 55–62. 10.1086/301936 CASPubMedWeb of Science®Google Scholar Waterham HR, Wanders RJ. 2000. Biochemical and genetic aspects of 7-dehydrocholesterol reductase and Smith-Lemli-Opitz syndrome. Biochim Biophys Acta 1529: 340–356. 10.1016/S1388-1981(00)00159-1 CASPubMedWeb of Science®Google Scholar Witsch-Baumgartner M, Fitzky BU, Ogorelkova M, Kraft HG, Moebius FF, Glossmann H, Seedorf U, Gillessen-Kaesbach G, Hoffmann GF, Clayton P, Kelley RI, Utermann G. 2000. Mutational spectrum in the δ7-sterol reductase gene and genotype–phenotype correlation in 84 patients with Smith-Lemli-Opitz syndrome. Am J Hum Genet 66: 402–412. 10.1086/302760 CASPubMedWeb of Science®Google Scholar Yu H, Lee MH, Starck L, Elias ER, Irons M, Salen G, Patel SB, Tint GS. 2000. Spectrum of δ(7)-dehydrocholesterol reductase mutations in patients with the Smith-Lemli-Opitz (RSH) syndrome. Hum Mol Genet 9: 1385–1391. 10.1093/hmg/9.9.1385 CASPubMedWeb of Science®Google Scholar Citing Literature Volume103, Issue41 November 2001Pages 344-347 ReferencesRelatedInformation

Crack, the free-base form of cocaine, causes pulmonary, cardiac, obstetric, neurologic, muskuloskeletal, and gastrointestinal complications. As the popularity for crack use increases, it follows that the number of cocaine-related emergency department (ED) visits, hospitalizations, and deaths should increase. We report 3 cases of patients arriving to the ED with acute onset of abdominal pain after smoking crack. These patients required surgical correction of their intestinal perforations. Although the exact pathophysiology of intestinal ischemia is not known, cocaine blocks the reuptake of norepinephrine, which leads to mesenteric vasoconstriction and focal tissue ischemia that may lead to perforation. The chronologic relationship of crack consumption to gastrointestinal perforation leads us to surmise that a possible crack-related ischemic event is the cause of perforation in these patients. Physicians examining patients with abdominal pain should be aware of the potential gastrointestinal complications of crack and consider bowel ischemia whenever a cocaine abuser presents with abdominal pain. (Am J Emerg Med 2001; 19:61-63. Copyright © 2001 by W.B. Saunders Company)

Blastomycosis is an unusual fungal infection in children. It is often a chronic infection characterized by granulomatous and suppurative lesions. Clinical manifestations include either pulmonary findings or disseminated disease. Disseminated blastomycosis usually begins with a lung infection that spreads to the skin, bones, and central nervous system. This is a case report of a child with chronic blastomycosis presenting with chronic paronychia, fever, cough, malaise, and back pain. The child underwent surgical drainage of a paravertebral abscess and administration of intravenous amphotericin B. He was discharged in good condition on oral therapy with ketoconazole. The literature on blastomycosis, with particular emphasis on clinical presentations and management, is reviewed. When the history and physical examination suggest a chronic granulomatous or disseminated disease, such as tuberculosis, the physician must include blastomycosis in the differential.

Mutations of the human Patched gene ( PTCH ) have been identified in individuals with the nevoid basal cell carcinoma syndrome (NBCCS) as well as in sporadic basal cell carcinomas and medulloblastomas. We have isolated a homologue of this tumour suppressor gene and localized it to the short arm of chromosome 1 (1p32.1-32.3). Patched 2 ( PTCH2 ) comprises 22 coding exons and spans approximately 15 kb of genomic DNA. The gene encodes a 1203 amino acid putative transmembrane protein which is highly homologous to the PTCH product. We have characterized the genomic structure of PTCH2 and have used single-stranded conformational polymorphism analysis to search for mutations in PTCH2 in NBCCS patients, basal cell carcinomas and in medulloblastomas. To date, we have identified one truncating mutation in a medulloblastoma and a change in a splice donor site in a basal cell carcinoma, suggesting that the gene plays a role in the development of some tumours.

The Cdx2 gene is one of three murine homologues of the Drosophila homeobox gene caudal. Mice heterozygous for a null mutation in Cdx2 exhibit a variable phenotype including tail abnormalities, stunted growth and a homeotic shift of vertebrae. Most strikingly, however, 90% of heterozygous mice were reported to develop multiple intestinal adenomatous polyps, most notably in the proximal colon (). These observations led us to propose that mutation of CDX2 may be involved in the genesis of some human colorectal tumours. A survey of DNA from 85 colorectal tumours revealed that one with extensive microsatellite instability (RER+ phenotype) has mutations in both alleles of CDX2. Both mutations occur in coding regions which contain repetitive elements and are consistent with those found in RER+ tumours.

The human homologue of the Drosophila segment polarity gene patched is mutated in the cancer predisposition syndrome naevoid basal cell carcinoma syndrome (NBCCS), as well as in several types of tumour associated with the disorder. It was recently reported that a single recurrent mutation in the SONIC HEDGEHOG gene, which encodes the PATCHED ligand, was found in one of 43 basal cell carcinomas (BCCs), one of 14 medulloblastomas and one of six breast carcinomas analysed (. We have searched extensively for this same mutation in a large collection of BCCs, medulloblastomas and carcinomas of the breast, ovary and colorectum and have failed to detect the mutation in any sample analysed.