MAIN RESEARCH PROJECTS
Role and mechanisms of the embryonic dorsal midline formation
in neural development. Molecular signalling, proliferation and cell
We have previously shown that the specification of the structures
that compose the embryonic dorsal midline (DML) in Xenopus laevis
is modulated by Delta-Notch signalling. By activating its target
gene hairy2a, Notch triggers a binary decision within the Spemann’s
organiser, favouring the floor plate fate at the expense of the
notochord (López et al., 2003; 2005). Recent evidences suggest
that neuralisation in Xenopus begins before the formation of the
Spemann’s organiser. The aims of this research topic are to
study neural induction, patterning, survival and proliferation in
the absence of DML structures after molecular ablation of the organiser.
We will also study the role of Numb, Sonic Hedgehog and retinoid
signalling in the molecular and cellular organisation of the floor
plate in Xenopus.
Role of Notch signaling in the early development of Xenopus
Preliminary results suggest that the control of Notch signalling
on the DML structures may be extensive to the entire marginal zone,
by promoting neural fates at the expense of mesoderm. In addition,
we have recently found that Notch is able to down-regulate the expression
of chordin in the BCNE center, suggesting earlier functions for
this signaling pathway that may be cross-talking with the Wnt/ß-catenin
cascade during dorsal determination.
We also described that overexpression of hairy-2a represses the
pan mesodermal marker brachyury in all locations and the dorsal
marker chordin in the Spemann-Mangold organiser. However, chordin
is ectopically activated in ventral and lateral locations, where
the normal expression of hairy-2a is lower or undetectable (López
et al., 2005). Preliminary results suggest that brachyury and hairy-2a
may be involved in a cross-regulatory network controlling dorsal
and ventral fates.
The aims of this research topic are to study: A) The role of Notch
in the development of the BCNE center and possible interactions
with the Wnt/ß-catenin pathway. B) Functional relationships
between brachyury and hairy-2a in the development of the dorsal-ventral
axis. C) The role of Notch in the marginal zone.