Anti-TCF3 (N-terminal) polyclonal antibody

Phenotype driven genetic screens allow unbiased exploration of the genome to discover new biological regulators. Bloom syndrome gene (Blm) deficient embryonic stem (ES) cells provide an opportunity for recessive screening due to frequent loss of heterozygosity. We describe a strategy for isolating regulators of mammalian pluripotency based on conversion to homozygosity of PiggyBac gene trap insertions combined with stringent selection for differentiation resistance. From a screen of 2000 mutants we obtained a disruptive integration in the Tcf3 gene. Homozygous Tcf3 mutants showed impaired differentiation and enhanced self-renewal. This phenotype was reverted in a dosage sensitive manner by excision of one or both copies of the gene trap. These results provide new evidence confirming that Tcf3 is a potent negative regulator of pluripotency and validate a forward screening methodology to identify modulators of pluripotent stem cell biology.

Epithelial-mesenchymal transition (EMT) is a feature of migratory cellular processes in all stages of life, including embryonic development and wound healing. Importantly, EMT features cluster with disease states such as chronic fibrosis and cancer. The dissolution of the E-cadherin-mediated adherens junction (AJ) is a key preliminary step in EMT and may occur early or late in the growing epithelial tumour. This is a first step for tumour cells towards stromal invasion, intravasation, extravasation and distant metastasis. The AJ may be inactivated in EMT by directed E-cadherin cleavage; however, it is increasingly evident that the majority of AJ changes are transcriptional and mediated by an expanding group of transcription factors acting directly or indirectly to repress E-cadherin expression. A review of the current literature has revealed that these factors may regulate each other in a hierarchical pattern where Snail1 (formerly Snail) and Snail2 (formerly Slug) are initially induced, leading to the activation of Zeb family members, TCF3, TCF4, Twist, Goosecoid and FOXC2. Within this general pathway, many inter-regulatory relationships have been defined which may be important in maintaining the EMT phenotype. This may be important given the short half-life of Snail1 protein. We have investigated these inter-regulatory relationships in the mesenchymal breast carcinoma cell line PMC42 (also known as PMC42ET) and its epithelial derivative, PMC42LA. This review also discusses several newly described regulators of E-cadherin repressors including oestrogen receptor-alpha and new discoveries in hypoxia-and growth factor-induced EMT. Finally, we evaluated how these findings may influence approaches to current cancer treatment. Copyright (C) 2010 S. Karger AG, Basel