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Principal investigator Dr. Pujades
- Study of the molecular mechanisms involved in the patterning of the hindbrain
- Analysis of the molecular signals from the hindbrain involved in inner ear patterning

 

Study of the molecular mechanisms involved in the patterning of the hindbrain

C. Vázquez-Echeverría, F. Aragón, C. Pujades

The generation of distinct cell types in a precise number and location within the neural tube is essential for the formation of the circuits responsible for all animal behaviour. The first manifestation of this diversity is the regionalisation of the neural tube along the antero-posterior (AP) and dorso-ventral (DV) axis. AP patterning of the hindbrain involves segmentation, leading to the formation of morphological bulges called rhombomeres (r). They constitute cellular compartments and units of gene expression and cell lineage. Although the regulation of the gene network in the hindbrain has been partially elucidated, we know very little about the molecular players involved in early steps of hindbrain segmentation. We are interested in dissecting the molecular mechanisms underlying the AP patterning of the neural tube, the future Central Nervous System in the vertebrates.

  1. How each rhombomere can establish and maintain a specific segmental identity?
    During embryonic development, it is often the case that cells are specified or committed to different fates before morphological distinctions between cells or territories can be discerned. This commitment is presumably accompanied by changes in gene expression. However, as most transcriptional assays are performed on populations of cells, it has not been possible to determine whether all cells within a sample are expressing the same set of genes. We want therefore to explore the use of transcriptional profiling in single cells, in the context of hindbrain development, by analysing cells when rhombomeres first establishes and cell commitment is just beginning. We generated cDNA populations corresponding to the different presumptive rhombomeric territories and a differential hybridisation is carried out with mice microarrays (Agilent). Differentially expressed genes can have a role either in the segmentation process or in the specification of the identity of the segment. Finally, we plan to the investigate the function and regulation of those newly characterised genes.
  2. Which is the role of the homeodomain-containing gene variant Hepatocyte Nuclear Factor-1 (vHnf1) in early stages of neural development?
    We have previously described that misexpression of vHnf1 within the neural tube of chick embryos confers caudal identity to more anterior regions of the hindbrain through FGF signals (Aragón et al., 2005). We are currently dissecting the intracellular FGF-pathway involved in hindbrain development, and investigating other signalling pathways that could play a role in hindbrain patterning as mediators of vHnf1 action.

 

Publications

Lecaudey, V., Ulloa, E., Anselme , I., Stedman, A., Schneider-Maunoury, S., Pujades, C. (2006) Role of the hindbrain in patterning the otic vesicle: A study of the zebrafish vhnf1 mutant. Dev. Biol. 292(1), pp. 55-67, 2006

Pujades, C., Kamaid, A., Alsina, B., Giráldez, F. (2006) BMP-signaling regulates the generation of hair-cells . Dev. Biol. 303(1), pp. 134-43, 2006

Aragón, F., Vazquez-Echeverría, C., Ulloa, E., Reber, M., Cereghini, S., Alsina, B., Giráldez, F., Pujades, C. (2005) vHnf1 regulates specification of caudal rhombomere identity in the chick hindbrain. Dev. Dyn. 234(3), pp. 567-76, 2005

F. Mechta-Grigoriu, F. Giudicelli, C. Pujades, P. Charnay, M. Yaniv (2003) kreisler controls c-jun regulation and function in the developing hindbrain. Dev. Biol. 258, pp. 419-431

O. Voiculescu, E. Taillebourg, C. Pujades, C. Kress, S. Buart, P. Charnay, S. Schneider-Maunory (2001) Krox20 controls multiple steps in the specification of rhombomeres 3 and 5. Development 128, pp. 4967-4978

F. Helmbacher, C. Pujades, C. Desmarquet, M. Frain, F. Rijli, P. Chambon, P. Charnay (1998) Hoxa-1 and Krox-20 synergize in the patterning of rhombomere 3. Development 125, pp. 4739-4748

Lumsden, A., Krumlauf, R. (1996) Patterning the vertebrate neuraxis. Science 274, pp. 1109-15

 

Analysis of the molecular signals from the hindbrain involved in inner ear patterning

C. Vázquez-Echeverría. E. Ulloa, C. Pujades

Development of the inner ear requires interaction with adjacent hindbrain tissue that would provide inductive signals that specify positional information to the otic vesicle. Mice mutants with defects in the hindbrain region are often associated with inner ear malformations. The main focus of our research is the analysis of hindbrain molecular signals involved in axial specification of the inner ear.

  1. Analysis of otic patterning genes in mice embryos mutants for hindbrain specific genes
    There are few evidences showing how the inner ear sensory domains are established at early stages of otic development in mice embryos. In order to study whether the hindbrain signals are relevant in the regionalization of the otic vesicle, we have first carefully characterised the expression profile of otic patterning and neurogenic genes at early stages of otic development in mice embryos (Vazquez-Echeverria et al., in preparation), and established how the sensory and non-sensory regions are generated. We are currently investigating how otic patterning is affected in kreisler mutants.
  2. How hindbrain signals instruct the otic vesicle patterning in vhnf1hi2169 zebrafish mutants?
    The recent isolation of hypomorphic mutant alleles of vhnf1 gene in zebrafish, which embryos display otic vesicles reduced in size supports the idea that the otic anomaly results from patterning defects in the hindbrain. To explore that more deeply we study the patterning of the otic primordium in vhnf1hi2169 mutants (Sun and Hopkins, 2001). We have observed that reduction in size of the otic vesicle is due neither to smaller otic placodes nor apoptosis, but defects in AP patterning resulting in a misorganization of neurosensory elements of the sensory patches (Lecaudey et al., submitted).

 

Publications

Lecaudey, V., Ulloa, E., Anselme, I., Schneider-Maunoury, S., Pujades, C. Role of the hindbrain in patterning the otic vesicle: a study of the zebrafish vhnf1 mutant. Submitted, 2006

Sun, Z. and Hopkins (2002) vhnf1, the MODY5 and familial GCKD-associated gene, regulates regional specification of the zebrafish gut, pronephros and hindbrain. Gens and Dev. 15, 3217-3229

Torres, M. and Giraldez, F. (1998) The development of the vertebrate inner ear. Mech. Dev. 71, 5-21

Brigande, J., Kiernan, X. Gao, A. Iten, D. Fekete (2000) Molecular genetics of pattern formation in the inner ear: Do compartment boundaries play a role? PNAS 97, 11700-11706

Fekete, DM., Wu, DK. (2002) Revisiting cell fate specification in the inner ear. Cur. Op. in Neurobiol. 12, 35-42

 

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