Regulation of Hox activity: insights from protein motifs.

Deciphering the molecular bases of animal body plan construction is a central question in developmental and evolutionary biology. Genome analyses of a number of metazoans indicate that widely conserved regulatory molecules underlie the amazing diversity of animal body plans, suggesting that these molecules are reiteratively used for multiple purposes. Hox proteins constitute a good example of such molecules and provide the framework to address the mechanisms underlying transcriptional specificity and diversity in development and evolution.

Fluorescence imaging techniques for studying Drosophila embryo development.

This unit describes fluorescence-based techniques for noninvasive imaging of development in living Drosophila embryos, discussing considerations for fluorescent imaging within living embryos and providing protocols for generation of flies expressing fluorescently tagged proteins and for preparation of embryos for fluorescent imaging. The unit details time-lapse confocal imaging of live embryos and discusses optimizing image acquisition and performing three-dimensional imaging. Finally, the unit provides a variety of specific methods for optical highlighting of specific subsets of fluorescently tagged proteins and organelles in the embryo, including fluorescence recovery after photobleaching (FRAP), fluorescence loss in photobleaching (FLIP), and photoactivation techniques, permitting analysis of specific movements of fluorescently tagged proteins within cells.

In vitro migration assays of neural stem cells.

We describe three rapid procedures for the in vitro investigation of molecular factors influencing the migration of neural precursors derived from embryonic or postnatal neural stem cells. In the first assay, factors influencing chain migration from the anterior subventricular zone of perinatal mice can be analyzed after explantation and embedding in Matrigel, a three-dimensional substrate mimicking the in vivo extracellular matrix. The second assay enables to assess soluble factors influencing radial migration away from adherent neurospheres in which embryonic stem cells have been expanded.

Characterization of heterogeneous glial cell populations involved in dehydration-induced proliferation in the adult rat neurohypophysis.

The adult neurohypophysis (NH) is a well-established site of CNS plasticity: its glial cells, the pituicytes, reorganize their structure and undergo increased proliferation in response to stimulations such as dehydration. However, it remains to be clarified whether the newly-formed cells derive from pituicytes re-entering the cell cycle or from glial precursors or stem cells. Here, we first analyze the expression of several glial markers in the adult rat NH and demonstrate that the pituicytes constitute a heterogeneous population.

LIFR beta plays a major role in neuronal identity determination and glial differentiation in the mouse facial nucleus.

In the hindbrain, generation of the facial nucleus involves complex developmental processes that will lead to the formation of a structure composed of motor neurons, astrocytes and oligodendrocytes. The implication of LIF-related cytokines in the development of this nucleus came to light with the analysis of mice mutant for the receptor of these cytokines, LIFR beta, which exhibit a massive loss of facial branchiomotor (fbm) neurons at birth and a severe decrease in GFAP expression, a marker of astrocytes. To uncover the cellular mechanisms regulated by LIFR beta during facial nucleus development, we first analyzed its expression pattern in the hindbrain.

Control of planar divisions by the G-protein regulator LGN maintains progenitors in the chick neuroepithelium.

The spatio-temporal regulation of symmetrical as opposed to asymmetric cell divisions directs the fate and location of cells in the developing CNS. In invertebrates, G-protein regulators control spindle orientation in asymmetric divisions, which generate progeny with different identities. We investigated the role of the G-protein regulator LGN (also called Gpsm2) in spindle orientation and cell-fate determination in the spinal cord neuroepithelium of the developing chick embryo.

Cell surface mechanics and the control of cell shape, tissue patterns and morphogenesis.

Embryonic morphogenesis requires the execution of complex mechanisms that regulate the local behaviour of groups of cells. The orchestration of such mechanisms has been mainly deciphered through the identification of conserved families of signalling pathways that spatially and temporally control cell behaviour. However, how this information is processed to control cell shape and cell dynamics is an open area of investigation.