An amputation resets positional information to a proximal identity in the regenerating zebrafish caudal fin

Abstract

BackgroundZebrafish has emerged as a powerful model organism to study the process of regeneration. This teleost fish has the ability to regenerate various tissues and organs like the heart, spinal cord, retina and fins. In this study, we took advantage of the existence of an excellent morphological reference in the zebrafish caudal fin, the bony ray bifurcations, as a model to study positional information upon amputation. We investigated the existence of positional information for bifurcation formation by performing repeated amputations at different proximal-distal places along the fin.ResultsWe show that, while amputations performed at a long distance from the bifurcation do not change its final proximal-distal position in the regenerated fin, consecutive amputations done at 1 segment proximal to the bifurcation (near the bifurcation) induce a positional reset and progressively shift its position distally. Furthermore, we investigated the potential role of Shh and Fgf signalling pathways in the determination of the bifurcation position and observed that they do not seem to be involved in this process.ConclusionsOur results reveal that, an amputation near the bifurcation inhibits the formation of the regenerated bifurcation in the pre-amputation position, inducing a distalization of this structure. This shows that the positional memory for bony ray bifurcations depends on the proximal-distal level of the amputation.

Quantitative assessment of the regenerative and mineralogenic performances of the zebrafish caudal fin

“…Some are based on the number of newly mineralized segments in regenerating lepidotrichia2425, others have considered segment length or width1324, or the relative position or number of bifurcations1424. However, these measurements do not directly correlate with the rate of bone formation and mineralization; they are linked to the patterning and not to the extent of newly mineralized tissue.…”

“…For example, the total fin area or length of lepidotrichia 2 and 323, the length or width of segments1324, the number of newly mineralized segments within lepidotrichia2425 or the relative position or number of bifurcations1424. Also, transgenic tools have facilitated the study of osteogenesis by imaging fluorescent proteins expressed under the control of promoters or enhancers of bone marker genes like runx2, sp7 and osteocalcin 17.…”

Shh promotes direct interactions between epidermal cells and osteoblast progenitors to shape regenerated zebrafish bone

“…Shha is a candidate mediator of this signaling, as ptch2 ( previously called ptc1) is expressed in Obs adjacent to shha-expressing epidermal cells (Laforest et al, 1998;Murciano et al, 2007;Quint et al, 2002) and ectopic Shh promotes ray fusion and promiscuous bone formation (Quint et al, 2002). However, a role for Shha in ray branching has been questioned based on the suggestion that shha-expressing epidermal domains are constitutively split and that shha induction kinetics are inconsistent with Shha being the instructive ray bifurcation signal (Azevedo et al, 2012).…”

Autophagy is required for zebrafish caudal fin regeneration

“…It can replace up to one-fifth of its heart ventricle after injury, 5,6 and has a seemingly unlimited potential to regrow its caudal fin after amputation. 7,8 The zebrafish caudal fin has become a useful proxy to examine the paradigm of appendage regeneration. Similar to renewal of amphibian limbs, caudal fin regeneration starts from a highly proliferative tissue, the blastema, which is formed distal from the site of amputation via dedifferentiation and generates almost exclusively cells of the parent cell's type.…”