.... Polarity is anchored to tissues through organisers located at boundaries. We show how this intracellular partitioning-based framework can be applied to both plant and animal systems, allowing different processes to be placed in a common evolutionary and mechanistic context. To illustrate how...

... and cerebellum. Positioning of the mid-hindbrain boundary (MHB) within the neuroepithelium is dependent on the interface of Otx2 and Gbx2 expression domains, yet in the absence of either or both of these genes, organiser genes are still expressed, suggesting that other, as yet unknown mechanisms are also...

... that feedback upon these pathways. The homeodomain protein Hex, an early marker of anterior positional information, acts as a transcriptional repressor, suppressing induction and propagation of the Spemman organiser while specifying anterior identity. We show that Hex promotes anterior identity by amplifying...

... suggest patterning roles for anterior visceral endoderm (AVE) and ADE. Based on similarity of gene expression patterns, fate and a dual role in`protecting' the prospective forebrain from caudalising influences of the organiser, the chick hypoblast has been suggested to be the homologue of the mouse...

...Carol Irving; Amar Malhas; Sarah Guthrie; Ivor Mason Formation of the trochlear nerve within the anterior hindbrain provides a model system to study a simple axonal projection within the vertebrate central nervous system. We show that trochlear motor neurons are born within the isthmic organiser...

... and molecular characteristics. The medial region of the floor plate (MFP) is formed by cells originating from the avian organiser, Hensen’s node. During its rostrocaudal movement, which is concomitant with the posterior elongation of the embryo, the node leaves in its wake two closely associated axial...

... by the down-regulation of Goosecoid and Chordin , while induction of dorsal mesoderm by Hex-λVP2 results in activation of these genes. Transient transfection experiments in ES cells suggest that Goosecoid is a direct target of Hex. Together, our results support a model in which Hex suppresses organiser...

... of the Wnt dorsalisation pathway and triggers organiser activity in the absence of mesoderm . Development 122 , 3055 – 3065 10.1242/dev.122.10.3055 Conlon , F. L. , Sedgwick , S. G. , Weston , K. M. and Smith , J. C. ( 1996 ). Inhibition of Xbra transcription activation...

... mesendoderm which lacks dorsalising activity, can only be activated by the VCC/ Siamois pathway in vegetal cells. We propose that the regionalisation of the organiser during gastrulation proceeds from the differential interpretation along the animal-vegetal axis of the activation of the VCCβ-catenin/ Siamois...

... generate a well organised notochord ( Waddington, 1933 ; Gallera, 1971 ; Nieuw-koop et al. 1985 ; Dias and Schoenwolf, 1990 ). Our previous work revealed that somites are composed of cells from two separate regions of the definitive streak-stage embryo: the rostral part of the primitive streak...

... plan when grafted to the ventral marginal zone of a similarly aged host embryo ( Cooke et al . 1987 ). This replicates the natural control of this phase of development by the dorsal blastoporal lip when similarly grafted; the classical ‘organiser’ phenomenon. I have explored systematically the effect...