Turbellarian taxonomic database

Abstract / Notes

"In previous studies, we have shown that dorsoventral (DV) interaction evokes
not only blastema formation, but also morphogenetic events similar to those
that occur in regeneration. However, it is still unclear what kinds of signal
molecules are involved in the DV interaction. To investigate the signal systems
involved in the DV interaction, we focused on a noggin-like gene (Djnlg)
identified by the planarian EST project. Djnlg is the first noggin homologue
isolated from an invertebrate. In DjNLG, the positions of nine cysteine
residues which may be essential for dimer formation were well conserved, but
overall, the amino acid sequence of DjNLG did not show high similarity to the
sequences of vertebrate Noggins. Expression of Djnlg was observed only in the
proximal region of the branch structures in the brain of intact planarians,
suggesting that Djnlg may have a role in pattern formation in the brain.
Interestingly, transient strong expression of Djnlg was observed in the
amputated region of regenerating planarians. Djnlg-expressing cells were
detected beneath the muscle 9 h after amputation and were then detected in the
ventral subepidermal region of the blastema. The induction of Djnlg expression
by amputation was not affected by X-ray irradiation, even though the stem cells
were completely eliminated, implying the existence of signal-producing cells
which may provide a positional cue to the stem cells. In DV reversed grafting,
expression of Djnlg was strongly induced in the DV boundary between the host
and donor. These results suggest that ectopic DV interaction may induce
expression of Djnlg in the positional cue-producing cells, and that it might be
involved in stimulation of blastema formation as well as DV patterning of the
body."

Return to taxon listing