Synchronous and early activation of planarian Hox genes and the re-specification of body axes during regeneration in Dugesia (G.) tigrina (Turbellaria; Tricladida)
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Seven Hox cluster-related genes (Dthox-A to -G) have been isolated from the freshwater triclad Dugesia (G.) tigrina, their sequence compared to other Hox genes and their expression in intact and regenerating organisms analyzed by whole mount in situ hybridization. Sequence comparison analyses show high similarities of D. tigrina Hox genes to anterior and medial groups of coelomate Hox genes. Expression analyses show very early, synchronous, and overlapping expression of Dthox -A, -E, -G and -F in anterior, posterior and lateral regenerative tissues. At one hour of regeneration all Dthox genes studied showed a neat, clear expression at the wound boundary. Later, as the blastema grows, the expression area expands to more proximal regions covering the blastema and the distal postblastema regions. Blastemas formed by intercalary regeneration also show a synchronous expression of the same Hox genes though the onset of activation is much delayed. The finding that the same set of Hox genes is synchronously activated in anterior, posterior, intercalary and lateral regeneration is in sharp contrast to its well established role in specifying antero-posterior pattern during embryonic development. The implications of these results as regards ancestral versus co-opted roles of Hox genes in development and regeneration are discussed.
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- Baguñà, J., E. Saló & M. C. Auladell, 1989. Regeneration and pattern formation in planarians. III. Evidence that neoblasts are totipotent stem cells and the source of blastema cells. Development 107: 77–86.Google Scholar
- Baguñà, J., E. Saló, R. Romero, J. Garcia-Fernàndez, D. Bueno, A. Muñoz-Mármol, J. R. Bayascas-Ramírez & A. Casali, 1994. Regeneration and pattern formation in planarians: cells, molecules and genes. Zool. Sci. 11: 781–795.Google Scholar
- Balavoine G., 1997. The early emergence of platyhelminths is contradicted by the agreement between 18S rRNA and Hox genes data. C.r. Acad. Sci., Paris 320: 83–94.Google Scholar
- Brønsdted, H. V., 1969. Planarian Regeneration. Pergamon Press, London.Google Scholar
- Deveraux JP, P. Haeberli, O. Smithies, 1984. A comprehensive set of sequence analysis programs for the VAX. Nucl. Acids Res. 12: 387–395.Google Scholar
- Duboule, D., 1994. Temporal colinearity and the phylotypic progression: a basis for the stability of a vertebrate Bauplan and evolution of morphologies through heterochrony. Development Suppl., 135–142.Google Scholar
- Holland, P. W. H., 1993. Cloning genes using the polymerase chain reaction. In C. D. Stern & P. W. H. Holland (eds), Essential Developmental Biology. A Practical Approach. IRL Press, Oxford: 243–255.Google Scholar
- Saló, E. & J. Baguñà. 1989. Regeneration and pattern formation in planarians. II. Local origin and role of cell movements in blastema formation. Development 107: 69–76.Google Scholar