The Journal of Neuroscience, October 1, 2001, 21(19):7620-7629
The LIM-Homeodomain Gene Family in the Developing
Xenopus Brain: Conservation and Divergences with the
Mouse Related to the Evolution of the Forebrain
Isabelle
Bachy,
Philippe
Vernier, and
Sylvie
Rétaux
UPR 2197 "Développement, Evolution, Plasticité
du Système Nerveux," Institut de Neurobiologie Alfred Fessard,
Centre National de la Recherche Scientifique, 91198 Gif-sur-Yvette cedex, France
A comparative analysis of LIM-homeodomain (LIM-hd) expression
patterns in the developing stage 32 Xenopus brain is
presented. x-Lhx2, x-Lhx7, and
x-Lhx9 were isolated and their expression, together with that of x-Lhx1 and x-Lhx5,
was analyzed in terms of prosomeric brain development and LIM-hd
combinatorial code and compared with mouse expression data. The results
show an almost complete conservation of expression patterns in the
diencephalon. The Lhx1/5 and Lhx2/9
subgroups label the pretectum/ventral thalamus/zona limitans versus the dorsal thalamus, respectively, in
alternating stripes of expression in both species. Conversely, strong
divergences in expression patterns are observed between the
telencephalon of the two species for Lhx1/5 and
Lhx2/9. Lhx7 exhibits particularly conservative patterns
and is proposed as a medial ganglionic eminence marker. The
conservation of diencephalic segments is proposed to mirror the
conservative nature of diencephalic structures across vertebrates. In
contrast, the telencephalic divergences are proposed to reflect the
emergence of significant novelty in the telencephalon (connectivity
changes) at the anamniote/amniote transition. Moreover, the data allow
the new delineation of pallial and subpallial domains in the developing
frog telencephalon, which are compared with mouse subdivisions. In the
pallium, the mouse combinatorial expression of LIM-hd is notably richer
than in the frog, again possibly reflecting evolutionary changes in
cortical connectivity.
Key words:
LIM-homeodomain; Xenopus; mouse; pallium; subpallium; prosomere; homology; connectivity
Copyright © 2001 Society for Neuroscience 0270-6474/01/21197620-10$05.00/0