92
M. Maden
Fig. 4.2 The effects of RA on the regenerating axolotl limb showing a graded series of PD duplications. Red line marks the amputation plane. a a control limb which regenerated precisely what
was removed. b a low concentration of RA caused the radius and ulna to be longer than expected.
c a medium concentration of RA caused the distal humerus followed by the lower arm and hand to
regenerate. d a high concentration of RA caused the regenerate to begin from the proximal humerus
level thereby regenerating a complete limb from the distal amputation plane. Lower graph shown
the increasing concentration needed to generate a complete limb, only 2.5-fold
• Is development the same as regeneration?
• Do all vertebrate limb/fin buds develop the same way with regards to RA?
• Do the forelimb buds develop in the same way as the hindlimb buds with regard
to RA?
• Is localized administration of RA on a bead the same as whole body immersion?
• Is RA an endogenous component of developing and regenerating limbs?
• Where in the limb is RA generated?
• Is there a gradient of RA in the limb?
Zebrafish Fin Development
Is RA Required?
Several approaches inhibiting RA signaling soon after gastrulation (Vandersea et al.
1998; Begemann et al. 2004; Gibert et al. 2006) demonstrated that RA is required
for pectoral fin bud initiation. Therefore, RA was required between the end of
gastrulation and up to the six-somite stage, long before the pectoral fin bud itself
appears.
M. Maden
Fig. 4.2 The effects of RA on the regenerating axolotl limb showing a graded series of PD duplications. Red line marks the amputation plane. a a control limb which regenerated precisely what
was removed. b a low concentration of RA caused the radius and ulna to be longer than expected.
c a medium concentration of RA caused the distal humerus followed by the lower arm and hand to
regenerate. d a high concentration of RA caused the regenerate to begin from the proximal humerus
level thereby regenerating a complete limb from the distal amputation plane. Lower graph shown
the increasing concentration needed to generate a complete limb, only 2.5-fold
• Is development the same as regeneration?
• Do all vertebrate limb/fin buds develop the same way with regards to RA?
• Do the forelimb buds develop in the same way as the hindlimb buds with regard
to RA?
• Is localized administration of RA on a bead the same as whole body immersion?
• Is RA an endogenous component of developing and regenerating limbs?
• Where in the limb is RA generated?
• Is there a gradient of RA in the limb?
Zebrafish Fin Development
Is RA Required?
Several approaches inhibiting RA signaling soon after gastrulation (Vandersea et al.
1998; Begemann et al. 2004; Gibert et al. 2006) demonstrated that RA is required
for pectoral fin bud initiation. Therefore, RA was required between the end of
gastrulation and up to the six-somite stage, long before the pectoral fin bud itself
appears.