Pilot series of radiofrequency ablation of Barrett's esophagus with or without neoplasia.

BACKGROUND AND STUDY AIMS: Radiofrequency ablation is a rapidly evolving therapeutic modality for Barrett's esophagus. The aim of this ongoing 12-month trial is to assess Barrett's esophagus eradication after radiofrequency ablation using a balloon-based (HALO-360) and a plate-based (HALO-90) device. We report here our experience with the first 10 patients (out of 40) who have completed 12 months of follow-up. PATIENTS AND METHODS: Following radiofrequency ablation using the HALO-360 device all patients were maintained on double-dose proton pump inhibitor therapy. Endoscopic evaluation was performed at 3 and 12 months postablation. Patients with residual Barrett's esophagus at 3 months underwent repeat ablation. Ten patients, seven with nondysplastic Barrett's esophagus, two with low-grade and one with high-grade dysplasia have completed the study to date. RESULTS: Complete Barrett's esophagus eradication was achieved in seven patients, and partial eradication was achieved in three. There were no major complications. One case of buried Barrett's metaplasia was encountered and successfully re-ablated, with complete Barrett's esophagus eradication achieved at 12 months. CONCLUSIONS: In this study, Barrett's eradication rates were comparable to previously published reports. One case of buried Barrett's metaplasia was identified out of 247 biopsies and was eradicated with repeat ablation.

Ligand-induced signaling in the absence of furin processing of Notch1.

Notch is a conserved cell surface receptor that is activated through direct contact with neighboring ligand-expressing cells. The primary 300-kDa translation product of the Notch1 gene (p300) is cleaved by a furin-like convertase to generate a heterodimeric, cell-surface receptor composed of 180- (p180) and 120- (p120) kDa polypeptides. Heterodimeric Notch is thought to be the only form of the receptor which is both present on the cell surface and able to generate an intracellular signal in response to ligand. Consistent with previous reports, we found that disruption of furin processing of Notch1, either by coexpression of a furin inhibitor or by mutation of furin target sequences within Notch1 itself, perturbed ligand-dependent signaling through the well-characterized mediator of Notch signal transduction, CSL (CBF1, Su(H), and LAG-1). Yet contrary to these reports, we could detect the full-length p300 Notch1 product on the cell surface. Moreover, this uncleaved form of Notch1 could suppress the differentiation of C2C12 myoblasts in response to ligand. Taken together, these data support our previous studies characterizing a CSL-independent Notch signaling pathway and identify this uncleaved isoform of Notch as a potential mediator of this pathway. Our results suggest a novel paradigm in signal transduction, one in which two isoforms of the same cell-surface receptor could mediate two distinct signaling pathways in response to ligand.

Fringe differentially modulates Jagged1 and Delta1 signalling through Notch1 and Notch2.

Proteins encoded by the fringe family of genes are required to modulate Notch signalling in a wide range of developmental contexts. Using a cell co-culture assay, we find that mammalian Lunatic fringe (Lfng) inhibits Jagged1-mediated signalling and potentiates Delta1-mediated signalling through Notch1. Lfng localizes to the Golgi, and Lfng-dependent modulation of Notch signalling requires both expression of Lfng in the Notch-responsive cell and the Notch extracellular domain. Lfng does not prevent binding of soluble Jagged1 or Delta1 to Notch1-expressing cells. Lfng potentiates both Jagged1- and Delta1-mediated signalling via Notch2, in contrast to its actions with Notch1. Our data suggest that Fringe-dependent differential modulation of the interaction of Delta/Serrate/Lag2 (DSL) ligands with their Notch receptors is likely to have a significant role in the combinatorial repertoire of Notch signalling in mammals.

Notch receptor activation inhibits oligodendrocyte differentiation.

In this study, we show that oligodendrocyte differentiation is powerfully inhibited by activation of the Notch pathway. Oligodendrocytes and their precursors in the developing rat optic nerve express Notch1 receptors and, at the same time, retinal ganglion cells express Jagged1, a ligand of the Notch1 receptor, along their axons. Jagged1 expression is developmentally regulated, decreasing with a time course that parallels myelination in the optic nerve. These results suggest that the timing of oligodendrocyte differentiation and myelination is controlled by the Notch pathway and raise the question of whether localization of myelination is controlled by this pathway.

Expression patterns of Jagged, Delta1, Notch1, Notch2, and Notch3 genes identify ligand-receptor pairs that may function in neural development.

Notch genes encode receptors for a signaling pathway that regulates neurogenesis. The DSL (Delta/Serrate/lag-2) genes encode ligands that bind and activate Notch. In situ hybridization was used to determine the spatiotemporal expression of Notch1, Notch2, and Notch3, and the DSL ligands, Jagged and Delta 1, in an effort to identify potential ligand-receptor pairs that function during development of the rat nervous system. Here we describe both distinct and overlapping expression patterns for these genes in neural progenitors that form both the central and the peripheral nervous systems. The punctate expression patterns we detected for Jagged and Delta 1 are consistent with their role in mediating lateral inhibition, a process proposed to regulate neural determination. Furthermore, within the ventricular zone of the neural tube and retina, Jagged and Delta 1 were expressed in complementary regions, suggesting that different DSL-Notch combinations may direct the development of distinct neural subtypes.

The development of sequence-tagged sites for human chromosome 4.

As part of our efforts to construct a high-resolution physical map of human chromosome 4, we developed a systematic approach for efficiently generating large numbers of chromosome-specific sequence-tagged sites (STSs). In this paper, we describe how rate-limiting steps in our STS development were identified and overcome, and detail our current development strategy. We present information for 822 new human chromosome 4-specific STSs, including PCR amplification conditions and subchromosomal localization data, obtained by analysis of the STS with somatic cell hybrids containing different portions of human chromosome 4. Although most STSs presented here were developed from anonymous clones whose sequences were determined in this laboratory, several STSs were developed for genes and other DNA sequences that were previously mapped to chromosome 4. Our data indicate that the availability of DNA sequence for an STS locus, in addition to the sequences of the two PCR oligonucleotides, significantly increases the transfer of that STS by allowing investigators to select new oligonucleotides best suited to the standard conditions used in their laboratories.

Identification of polymorphisms by genomic denaturing gradient gel electrophoresis: application to the proximal region of human chromosome 21.

Genomic Denaturing Gradient Gel Electrophoresis (gDGGE) provides an alternative to the standard method of restriction fragment length polymorphism (RFLP) analysis for identifying polymorphic sequence variation in genomic DNA. For gDGGE, genomic DNA is cleaved by restriction enzymes, separated in a polyacrylamide gel containing a gradient of DNA denaturants, and then transferred by electroblotting to nylon membranes. Unlike other applications of DGGE, gDGGE is not limited by the size of the probe and does not require probe sequence information. gDGGE can be used in conjunction with any unique DNA probe. Here we use gDGGE with probes from the proximal region of the long arm of human chromosome 21 to identify polymorphic DNA sequence variation in this segment of the chromosome. Our screening panel consisted of DNA from nine individuals, which was cleaved with five restriction enzymes and submitted to electrophoresis in two denaturing gradient conditions. We detected at least one potential polymorphism for nine of eleven probes that were tested. Two polymorphisms, one at D21S4 and one at D21S90, were characterized in detail. Our study demonstrates that gDGGE is a fast and efficient method for identifying polymorphisms that are useful for genetic linkage analysis.