Maintenance of blastemal proliferation by functionally diverse epidermis in regenerating zebrafish fins

Abstract

Appendage regeneration in salamanders and fish occurs through formation and maintenance of a mass of progenitor tissue called the blastema. A dedicated epidermis overlays the blastema and is required for its proliferation and patterning, yet this interaction is poorly understood. Here, we identified molecularly and functionally distinct compartments within the basal epidermal layer during zebrafish fin regeneration. Proximal epidermal subtypes express the transcription factor lef1 and the blastemal mitogen shh, while distal subtypes express the Fgf target gene pea3 and wnt5b, an inhibitor of blastemal proliferation. Ectopic overexpression of wnt5b reduced shh expression, while pharmacologic introduction of a Hh pathway agonist partially rescued blastemal proliferation during wnt5b overexpression. Loss- and gain-of-function approaches indicate that Fgf signaling promotes shh expression in proximal epidermis, while Fgf/Ras signaling restricts shh expression from distal epidermis through induction of pea3 expression and maintenance of wnt5b. Thus, the fin wound epidermis spatially confines Hh signaling through the activity of Fgf and Wnt pathways, impacting blastemal proliferation during regenerative outgrowth.

Retinoic acid signaling spatially restricts osteoblasts and controls ray-interray organization during zebrafish fin regeneration

“…shha is expressed within the basal epidermal layer adjacent to pre-and differentiating osteoblasts (supplementary material Fig. S1) (Laforest et al, 1998;Lee et al, 2009;Quint et al, 2002;Zhang et al, 2012). We found a similar expression pattern for the RA-degrading enzyme cyp26a1 (Fig.…”

“…Proliferation of preosteoblasts has been suggested to be controlled by Shha (Laforest et al, 1998;Lee et al, 2009;Quint et al, 2002;Zhang et al, 2012). We found reduced osteoblast proliferation within 12 h of cyclopamine treatment (Fig.…”

“…We did not observe shha expression in interrays. We propose that this was due to the requirement for Fgfs (and putative other blastemaderived signals) for shha expression (Lee et al, 2009). …”

Transcriptional components of anteroposterior positional information during zebrafish fin regeneration

“…However, shha is expressed in epidermal cells at the distal tip of each uninjured and regenerating adult fin ray, regardless of whether that ray expresses hand2 (Quint et al, 2002;Lee et al, 2009). We examined our RNA-Seq dataset for possible alternative targets of hand2 during regeneration, with a focus on genes known to be involved in bone formation or homeostasis.…”

Investigation into the healing properties of walnut (Tetracarpidium conophorum) leaf and onion (Allium cepa) bulb residues in Clarias gariepinus

“…Onions contain many active compounds that appear to inhibit the growth of cancerous cells, lower blood pressure and cholesterol and stimulate immune response. Some studies have been carried out in the cyprinid species zebra fish (Danio rerio) and common carp (Cyprinus carpio) (Nakatani et al 2007, Yoshinari et al 2009, Lee et al 2009, Wister albino rats, Rattus novergicus (Omale and Isaac 2010) but research studies on African catfish, Clarias gariepinus have not been properly elucidated.…”