Ephrin-B1 controls the columnar distribution of cortical pyramidal neurons by restricting their tangential migration.

Neurons of the cerebral cortex are organized in layers and columns. Unlike laminar patterning, the mechanisms underlying columnar organization remain largely unexplored. Here, we show that ephrin-B1 plays a key role in this process through the control of nonradial steps of migration of pyramidal neurons.

Mechanism of primitive duct formation in the pancreas and submandibular glands: a role for SDF-1.

Background: The exocrine pancreas is composed of a branched network of ducts connected to acini. They are lined by a monolayered epithelium that derives from the endoderm and is surrounded by mesoderm-derived mesenchyme. The morphogenic mechanisms by which the ductal network is established as well as the signaling pathways involved in this process are poorly understood.

Temporal regulation of ephrin/Eph signalling is required for the spatial patterning of the mammalian striatum.

Brain structures, whether mature or developing, display a wide diversity of pattern and shape, such as layers, nuclei or segments. The striatum in the mammalian forebrain displays a unique mosaic organization (subdivided into two morphologically and functionally defined neuronal compartments: the matrix and the striosomes) that underlies important functional features of the basal ganglia. Matrix and striosome neurons are generated sequentially during embryonic development, and segregate from each other to form a mosaic of distinct compartments.

An intrinsic mechanism of corticogenesis from embryonic stem cells.

The cerebral cortex develops through the coordinated generation of dozens of neuronal subtypes, but the mechanisms involved remain unclear. Here we show that mouse embryonic stem cells, cultured without any morphogen but in the presence of a sonic hedgehog inhibitor, recapitulate in vitro the major milestones of cortical development, leading to the sequential generation of a diverse repertoire of neurons that display most salient features of genuine cortical pyramidal neurons. When grafted into the cerebral cortex, these neurons develop patterns of axonal projections corresponding to a wide range of cortical layers, but also to highly specific cortical areas, in particular visual and limbic areas, thereby demonstrating that the identity of a cortical area can be specified without any influence from the brain.

Eph receptors and their ephrin ligands are expressed in developing mouse pancreas.

Pancreas development involves branching morphogenesis concomitantly to differentiation of endocrine, exocrine and ductal cell types from a single population of pancreatic precursors. These processes depend on many signals and factors that also control development of the central nervous system. In the latter, Eph receptors and their class-A (GPI-anchored) and class-B (transmembrane) ephrin ligands control cell migration and axon-pathfinding, help establish regional patterns and act as labels for cell positioning.

Ephrin signalling controls brain size by regulating apoptosis of neural progenitors.

Mechanisms controlling brain size include the regulation of neural progenitor cell proliferation, differentiation, survival and migration. Here we show that ephrin-A/EphA receptor signalling plays a key role in controlling the size of the mouse cerebral cortex by regulating cortical progenitor cell apoptosis. In vivo gain of EphA receptor function, achieved through ectopic expression of ephrin-A5 in early cortical progenitors expressing EphA7, caused a transient wave of neural progenitor cell apoptosis, resulting in premature depletion of progenitors and a subsequent dramatic decrease in cortical size.

Area specificity and topography of thalamocortical projections are controlled by ephrin/Eph genes.

The mechanisms generating precise connections between specific thalamic nuclei and cortical areas remain poorly understood. Using axon tracing analysis of ephrin/Eph mutant mice, we provide in vivo evidence that Eph receptors in the thalamus and ephrins in the cortex control intra-areal topographic mapping of thalamocortical (TC) axons. In addition, we show that the same ephrin/Eph genes unexpectedly control the inter-areal specificity of TC projections through the early topographic sorting of TC axons in an intermediate target, the ventral telencephalon.