Phosphorylation of Junb family proteins by the Jun N-terminal kinase supports tissue regeneration in zebrafish

Abstract

Tissue regeneration is fundamental for multi-cellular organisms to maintain their integrity, but the competence of tissue restoration is different depending on tissues, species, and ages. In spite of the recent progresses of the molecular basis of regeneration, little is known about its regulative processes. We previously identified the junb and junb-like (junbl) as transcripts induced in response to tissue injury in zebrafish. It has been demonstrated that the mammalian JunB is not phosphorylated by the Jun N-terminal kinase (JNK) due to the absence of a target site. Here, we show that the zebrafish Junb proteins retain the target site and are phosphorylated by the JNK. Significantly, we found that the phosphorylated Junb proteins (pJunbs) are necessary for adult and larval tissue regeneration, suggesting that the regulation of Junb proteins by phosphorylation is one of the molecular bases for the higher regeneration ability in zebrafish. We also show that the prolonged expression of junbs and their protein phosphorylation by the JNK after the wound healing stage are the unique and necessary features for regeneration. Thus, our data suggest that the transcriptional and post-transcriptional controls of junbs and their protein products are the important regulative steps that enable tissue regeneration in zebrafish.

Fgf signalling controls diverse aspects of fin regeneration

“…5A,B). Significantly, the expression of junbl, an earlier blastema marker (Ishida et al, 2010), was strongly and ectopically upregulated in and around the blastema (Fig. 5C,D), suggesting that fgf20a overexpression causes mesenchymal cells to acquire the distal blastema identity.…”

“…Immunostaining was performed on tissue sections according to a standard protocol (Ishida et al, 2010). Polyclonal anti-DsRed antibody (632393, Invitrogen) and anti-p63 antibody (ab97865, Abcam) were used at 1:1000.…”

“…Using a celltransplantation experiment of mesenchymal cells with inducible expression of fgfr1, we showed that Fgf signalling is directly required for the fin ray mesenchyme to form the blastema at the early pre-blastema stage and to activate the regenerative cell proliferation at a later post-blastema stage. Furthermore, we explored the specific functions of Fgf ligands by gain-of-function analyses and demonstrated that Fgf20a does indeed induce the distal blastema marker junbl ( junbb) (Yoshinari et al, 2009;Ishida et al, 2010), and that Fgf3 promotes cell proliferation in the blastema explants. Our study reveals the diverse roles of Fgf signals during fin regeneration in zebrafish and how Fgfs in the wound epidermis and blastema cooperatively regulate regeneration.…”

Impaired caudal fin‐fold regeneration in zebrafish deficient for the tumor suppressor Pten

“…Amputated zebrafish embryos obtained from a ptena +/− ptenb −/− in‐cross were fixed at 3 h post amputation (hpa) and subjected to in situ hybridization for detection of mmp9 transcription, which is a marker for the wound epithelium (Yoshinari, Ishida, Kudo, & Kawakami, 2009), and junbb and and1 transcription, both of which have previously been shown to be upregulated in the blastema (Thorimbert et al., 2015; Yoshinari et al., 2009). In fact, junbb expression is maintained well into the initial stage of regenerative outgrowth, indicating that junbb is a definitive distal blastema marker (Ishida, Nakajima, Kudo, & Kawakami, 2010). Both mmp9 and junbb were clearly induced by amputation of the caudal fin‐fold, and ptena −/− ptenb −/− mutant embryos expressed mmp9 and junbb to a similar extent as their siblings (Fig.…”

Adenosine enhances progenitor cell recruitment and nerve growth via its A2B receptor during adult fin regeneration

“…In invertebrates, it has been shown that apoptotic cells release Wnt and BMP signals that are directly responsible for compensatory proliferation in injured Drosophila imaginal discs [18] and head regeneration in hydra [8]. In mammals, it has been shown that during the process of apoptosis, activated caspases stimulate Ca2+-independent phospholipase A2 (iPLA2) to trigger the production of prostaglandin (PGE2), which in turn induces compensatory proliferation [19,20]. This induction of cell proliferation, via apoptosis/PGE2, near the dying cells is essential for skin wound healing and liver regeneration in mice.…”