Evolution of oesophageal adenocarcinoma from metaplastic columnar epithelium without goblet cells in Barrett's oesophagus.

Objective: Barrett's oesophagus commonly presents as a patchwork of columnar metaplasia with and without goblet cells in the distal oesophagus. The presence of metaplastic columnar epithelium with goblet cells on oesophageal biopsy is a marker of cancer progression risk, but it is unclear whether clonal expansion and progression in Barrett's oesophagus is exclusive to columnar epithelium with goblet cells.

Design: We developed a novel method to trace the clonal ancestry of an oesophageal adenocarcinoma across an entire Barrett's segment.

The Barrett's Gland in Phenotype Space.

Barrett's esophagus is characterized by the erosive replacement of esophageal squamous epithelium by a range of metaplastic glandular phenotypes. These glandular phenotypes likely change over time, and their distribution varies along the Barrett's segment. Although much recent work has addressed Barrett's esophagus from the genomic viewpoint-its the fact that the phenotype of Barrett's esophagus is nonstatic points to conversion between phenotypes and suggests that Barrett's esophagus also exists in .

The stem cell organisation, and the proliferative and gene expression profile of Barrett's epithelium, replicates pyloric-type gastric glands.

Objective: Barrett's oesophagus shows appearances described as 'intestinal metaplasia', in structures called 'crypts' but do not typically display crypt architecture. Here, we investigate their relationship to gastric glands.

Methods: Cell proliferation and migration within Barrett's glands was assessed by Ki67 and iododeoxyuridine (IdU) labelling.

sfrp1 promotes cardiomyocyte differentiation in Xenopus via negative-feedback regulation of Wnt signalling.

Wnt signalling is a key regulator of vertebrate heart development, yet it is unclear which specific Wnt signalling components are required to regulate which aspect of cardiogenesis. Previously, we identified Wnt6 as an endogenous Wnt ligand required for controlling heart muscle differentiation via canonical Wnt/β-catenin signalling. Here we show for the first time a requirement for an endogenous Wnt signalling inhibitor for normal heart muscle differentiation.

Inducible gene expression in transient transgenic Xenopus embryos.

Xenopus laevis has for many years been successfully used to study Wnt signaling during early development. However, because loss of function and gain of function experiments generally involve injecting RNA, DNA, or morpholinos into early embryos (1- to 32-cell), major phenotypes are often observed before the embryo has reached later stages of development. The combined use of transgenics and a heat shock inducible system has overcome these problems and enables investigations of Wnt signaling at later stages of Xenopus embryonic development, including organogenesis.

Gain-of-function and loss-of-function strategies in Xenopus.

Xenopus embryos are particularly suited for functional experiments to investigate vertebrate embryonic development. Due to the large size of embryos and their development outside of the mother organism, they are very accessible, easy to manipulate, and allow for immediate observation of developmental phenotypes. Powerful methods have been established for both gain- and loss-of-function strategies, which build on these inherent advantages.

Analysis of gene expression in Xenopus embryos.

Determining the expression pattern of a gene of interest is critical to understanding when, where, and how it may function during development. This chapter describes methods for determining the localization and expression levels for both mRNA and protein. Some of these methods can be described as quantitative or semi-quantitative while others are considered more qualitative in nature.

Wnt6 signaling regulates heart muscle development during organogenesis.

Mesodermal tissue with heart forming potential (cardiogenic mesoderm) is induced during gastrulation. This cardiogenic mesoderm later differentiates into heart muscle tissue (myocardium) and non-muscular heart tissue. Inhibition of Wnt/beta-catenin signaling is known to be required early for induction of cardiogenic mesoderm; however, the identity of the inhibiting Wnt signal itself is still elusive.

Wnt6 expression in epidermis and epithelial tissues during Xenopus organogenesis.

Here, we report the localization within embryonic tissues of xWnt6 protein; together with the temporal and spatial expression of Xenopus laevis Wnt6 mRNA. Wnt6 expression in Xenopus embryos is low until later stages of neurulation, when it is predominantly found in the surface ectoderm. Wnt6 expression increases during early organogenesis in the epidermis overlaying several developing organs, including the eye, heart, and pronephros.