Polymorphisms near TBX5 and GDF7 are associated with increased risk for Barrett's esophagus

BACKGROUND & AIMS

Barrett's esophagus (BE) increases the risk of esophageal adenocarcinoma (EAC). We found the risk to be BE has been associated with single nucleotide polymorphisms (SNPs) on chromosome 6p21 (within the HLA region) and on 16q23, where the closest protein-coding gene is FOXF1. Subsequently, the Barrett's and Esophageal Adenocarcinoma Consortium (BEACON) identified risk loci for BE and esophageal adenocarcinoma near CRTC1 and BARX1, and within 100 kb of FOXP1. We aimed to identify further SNPs that increased BE risk and to validate previously reported associations.

METHODS

We performed a genome-wide association study (GWAS) to identify variants associated with BE and further analyzed promising variants identified by BEACON by genotyping 10,158 patients with BE and 21,062 controls.

RESULTS

We identified 2 SNPs not previously associated with BE: rs3072 (2p24.1; odds ratio [OR] = 1.14; 95% CI: 1.09-1.18; P = 1.8 × 10(-11)) and rs2701108 (12q24.21; OR = 0.90; 95% CI: 0.86-0.93; P = 7.5 × 10(-9)). The closest protein-coding genes were respectively GDF7 (rs3072), which encodes a ligand in the bone morphogenetic protein pathway, and TBX5 (rs2701108), which encodes a transcription factor that regulates esophageal and cardiac development. Our data also supported in BE cases 3 risk SNPs identified by BEACON (rs2687201, rs11789015, and rs10423674). Meta-analysis of all data identified another SNP associated with BE and esophageal adenocarcinoma: rs3784262, within ALDH1A2 (OR = 0.90; 95% CI: 0.87-0.93; P = 3.72 × 10(-9)).

CONCLUSIONS

We identified 2 loci associated with risk of BE and provided data to support a further locus. The genes we found to be associated with risk for BE encode transcription factors involved in thoracic, diaphragmatic, and esophageal development or proteins involved in the inflammatory response.

Purpura fulminans: recognition, diagnosis and management

Purpura fulminans (PF) is a haematological emergency in which there is skin necrosis and disseminated intravascular coagulation. This may progress rapidly to multi-organ failure caused by thrombotic occlusion of small and medium-sized blood vessels. PF may complicate severe sepsis or may occur as an autoimmune response to otherwise benign childhood infections. PF may also be the presenting symptom of severe heritable deficiency of the natural anticoagulants protein C or protein S. Early recognition and treatment of PF is essential to reduce mortality and to prevent major long-term health sequelae. However, management strategies require accurate identification of the underlying cause. This review focuses on the clinical features, differential diagnosis and laboratory features of the range of PF disorders and includes expert consensus opinion about immediate and on-going management.

Tyr346-->Cys mutation results in factor VIII:C assay discrepancy and a normal bleeding phenotype - is this mild haemophilia A?

Patients with mild haemophilia A may have a discrepancy in the factor VIII (FVIII) level when measured with a one-stage assay (FVIII:C1) compared with a two-stage assay (FVIII:C2). This discrepancy usually results in the one-stage level being higher than the two-stage level. A F8 mutation resulting in a Tyr346-->Cys substitution within the a1 interdomain region has been described which results in the converse assay discrepancy. We report four individuals (three families) who have this mutation. Mean FVIII:C1 level was 25 IU dL(-1) compared with a mean FVIII:C2 level of 63 IU dL(-1). These individuals had presented opportunistically and did not have a clinically significant bleeding disorder. The bleeding phenotype correlated with the two-stage assay result rather than the one-stage result. FVIII replacement therapy does not appear to be required for these individuals.

Insulin-like growth factor expression in human cancer cell lines

The insulin-like growth factors (IGFs), IGF-I and IGF-II, are potent mitogens for human lung and other epithelial cancer cell lines. Previous studies in defined medium lacking added IGF or insulin suggest that an IGF-related ligand can act as an autocrine growth factor for many cancer cell lines through action via the type I IGF receptor (IGF-R). Analysis of RNA isolated from human lung and breast cancer cell lines by reverse transcription of mRNA and polymerase chain reaction reveal that IGF-I and IGF-II mRNAs were co-expressed with IGF-R in the majority of cell lines. IGF-I mRNA was detected in 11/12 small cell lung cancer cell lines (SCLC), 13/14 nonsmall cell lung cancer (NSCLC) cell lines, and 1/2 breast cancer cell lines. IGF-II mRNA was detected in 8/10 SCLC, 11/12 NSCLC cell lines, and 2/2 breast lines. All cell lines expressed IGF-R. For analysis of IGF peptide secretion, cell lines were adapted to growth in serum/hormone-free culture medium (R0), and to avoid interference by IGF-binding proteins, secreted IGF peptides were isolated under acidic conditions and analyzed by Western blotting. Based upon measurement of the sensitivity of the anti-IGF antibodies for detection of recombinant human IGFs, IGF peptides accumulated in conditioned medium at greater than picomolar concentrations should have been readily detected. In three cell lines (two lung and one breast) secreted IGF immunoreactivity was detected as three molecular mass species of 23, 14, and 6 kDa. Isolation and NH2-terminal sequencing of each of these species definitively identified them as differentially processed forms of the IGF-II prohormone. Despite the high frequency of IGF-I gene expression detected by reverse transcription-polymerase chain reaction analysis, only one lung cancer cell line, NCI-N417d, was found that unequivocally secreted IGF-I peptide. This direct sequence determination unambiguously identifies IGF-II as the predominant IGF involved in the autocrine growth stimulation of human lung and breast epithelial tumor cell lines and supports a growing body of literature that implicates IGF-II/IGF-R autocrine loops as a common growth mechanism in epithelial carcinogenesis.

The limbic system-associated membrane protein is an Ig superfamily member that mediates selective neuronal growth and axon targeting

The formation of brain circuits requires molecular recognition between functionally related neurons. We report the cloning of a molecule that participates in these interactions. The limbic system-associated membrane protein (LAMP) is an immunoglobulin (Ig) superfamily member with 3 Ig domains and a glycosyl-phosphatidylinositol anchor. In the developing forebrain, lamp is expressed mostly by neurons comprising limbic-associated cortical and subcortical regions that function in cognition, emotion, memory, and learning. The unique distribution of LAMP reflects its functional specificity. LAMP-transfected cells selectively facilitate neurite outgrowth of primary limbic neurons. Most striking, administration of anti-LAMP in vivo results in abnormal growth of the mossy fiber projection from developing granule neurons in the dentate gyrus of the hippocampal formation, suggesting that LAMP is essential for proper targeting of this pathway. Rather than being a general guidance cue, LAMP likely serves as a recognition molecule for the formation of limbic connections.

Lead poisoning from Asian traditional remedies in the West Midlands--report of a series of five cases

1. Traditional remedies are an unusual, but recognised cause of lead poisoning. Only two cases have previously been reported in this country. 2. We report a series of five cases of lead poisoning due to traditional remedies in the West Midlands. All developed typical clinical features. 3. Blood lead and zinc protoporphyrin (ZPP) concentrations were elevated 2-10 times the upper limit of normal. The remedies contained up to 60% lead by weight. One also contained traces of mercury, another arsenic, and a third aluminium and tin. 4. Confirmation of the medicines as the cause of the poisoning was made in one patient by measurement of lead isotopic ratios. 5. The present morbidity from traditional remedies may be far greater than is realised, and will continue until such time as the supply of harmful preparations can be effectively limited. There needs to be increased awareness of their dangers amongst doctors and the communities at risk. This will best be achieved by appropriately targeted education.

Identifying proteins from two-dimensional gels by molecular mass searching of peptide fragments in protein sequence databases

A rapid method for the identification of known proteins separated by two-dimensional gel electrophoresis is described in which molecular masses of peptide fragments are used to search a protein sequence database. The peptides are generated by in situ reduction, alkylation, and tryptic digestion of proteins electroblotted from two-dimensional gels. Masses are determined at the subpicomole level by matrix-assisted laser desorption/ionization mass spectrometry of the unfractionated digest. A computer program has been developed that searches the protein sequence database for multiple peptides of individual proteins that match the measured masses. To ensure that the most recent database updates are included, a theoretical digest of the entire database is generated each time the program is executed. This method facilitates simultaneous processing of a large number of two-dimensional gel spots. The method was applied to a two-dimensional gel of a crude Escherichia coli extract that was electroblotted onto poly(vinylidene difluoride) membrane. Ten randomly chosen spots were analyzed. With as few as three peptide masses, each protein was uniquely identified from over 91,000 protein sequences. All identifications were verified by concurrent N-terminal sequencing of identical spots from a second blot. One of the spots contained an N-terminally blocked protein that required enzymatic cleavage, peptide separation, and Edman degradation for confirmation of its identity.

Evidence supporting a role for cathepsin B in the generation of T cell antigenic epitopes of human growth hormone

The elucidation of the enzymatic processing mechanism associated with the formation of antigenic peptide fragments that combine with MHC class II molecules is fundamental to our understanding of the immune system. We have investigated a structurally well defined protein, recombinant human growth hormone (rhGH), as an antigen, and present data supporting the hypothesis that the enzyme cathepsin B can produce peptide fragments bearing T cell epitopes associated with lymphocyte proliferative response to hGH in Balb/c (H-2dhaplotype) mice. Minimal T cell epitopes are not generated; rather the cathepsin cleavage sites flank the three antigenic peptide regions, amino acid residues 31-41, 81-100, and 166-181.

An endothelial ligand for L-selectin is a novel mucin-like molecule

The adhesive interaction between circulating lymphocytes and the high endothelial venules (HEV) of lymph nodes (LN) is mediated by lymphocyte L-selectin, a member of the selectin family of cell adhesion proteins. Previous work has identified a sulfated 50 kd glycoprotein (Sgp50) as an HEV ligand for L-selectin. We now report the purification of this glycoprotein and the utilization of the derived N-terminal amino acid sequence to clone a cDNA. The predicted sequence reveals a novel, mucin-like molecule containing two serine/threonine-rich domains. The mRNA encoding this glycoprotein is preferentially expressed in LN. Antibodies against predicted peptides immunoprecipitate Sgp50 and stain the apical surface of LN HEV. These results thus define a tissue-specific mucin-like endothelial glycoprotein that appears to function as a scaffold that presents carbohydrates to the L-selectin lectin domain.

Transcription termination factor rho activity is altered in Escherichia coli with suA gene mutations

Rho factor has been purified from a strain of E. coli containing the Su78 mutation in the suA gene and assayed in another strain with an amber mutation in the suA gene. The rho from the Su78 mutant strain is present in normal amounts but has altered termination function; it does not terminate transcription at some sites that are recognized effectively by the rho factor from the isogenic wild-type strain. Rho in cells with an amber mutation in the suA gene has been assayed by its RNA-dependent ATPase activity. Extracts of cells of this strain have only 9% as much of this rho activity as extracts of cells of the isogenic wild-type strain. These results suggest that rho is the product of the suA gene. Since mutations in the suA gene are known to decrease polar effects of mutations in other genes, it is also suggested that rho factor is at least partially responsible for polar effects.