Retinoic Acid and Xenopus laevis Mesoderm Patterning

IBARRA M.A.; MONACO M.E.; VILLECCO E.I.; SANCHEZ S.S.

Carlos Paz, Córdoba, Argentina

Congreso; XLIV Reunion Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2008

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

During Xenopus laevis gastrulation different regions can be recognized in the mesodermal layer: head mesoderm, chordamesoderm, paraxial mesoderm and lateral plate mesoderm. Head mesoderm produces cephalic structures while paraxial mesoderm delivers somites. Although both mesoderm region give rise to the same tissue types (muscles and bones) they show distinct developmental programs. In order to elucidate the molecular setup of the head mesoderm and its relation to paraxial mesoderm we analyzed the expression of different molecular markers along the head-trunk patterning. We found head mesoderm is molecularly different from paraxial mesoderm. Only head mesoderm expresses Goosecoid, Tbx1 and Pitx2, while paraxial mesoderm molecular setup is represented by other markers as pMesogenin or Tbx6. Given that Retinoic Acid (RA) is involved in the patterning of the somitic mesoderm and considering that head mesoderm does not form somitic structures it is possible that head mesoderm is RA-free mesoderm. To prove this hypothesis we analyzed the expression pattern of RALDH2 (RA synthesis enzyme) and Cyp26 (RA hydroxylase). Cyp26 is expressed in head mesoderm and its overexpression produce alterations in the head-trunk mesoderm patterning. In avian embryos Cyp26 is also expressed only in head mesoderm. These findings led us to suggest that the head-trunk molecular pattern is evolutionary conserved