CgWnt-1 regulates haemocyte proliferation during immune response of oyster Crassostrea gigas

Recent findings regarding the immunomodulatory role of Wnt signaling suggest that it is significant in regulating the differentiation and proliferation of immune cells. In the present study, a Wnt-1 homolog (designated as CgWnt-1) with a conserved WNT1 domain was identified from oyster Crassostrea gigas. The transcripts of CgWnt1 were barely expressed in egg to gastrula stage during early embryogenesis, and up-regulated significantly in the trochophore to juvenile stage. The mRNA transcripts of CgWnt-1 were detected in different tissues of adult oyster, with an extremely high expression level in the mantle, which was 77.38-fold (p < 0.05) of that in labial palp. After Vibrio splendidus stimulation, the mRNA expression levels of CgWnt-1 and Cg8-catenin in haemocytes upregulated significantly at 3, 12, 24, and 48 h (p < 0.05). After injection of recombinant protein (rCgWnt-1) into oyster in vivo, the expressions of Cg8-catenin, cell proliferation related genes CgRunx-1 and CgCDK-2 in haemocytes significantly up-regulated, which were 4.86-fold (p < 0.05), 9.33-fold (p < 0.05), 6.09-fold (p < 0.05) of those in rTrx group, respectively. The percentage of EDU+ cells in haemocytes also significantly increased (2.88-fold of that in control group, p < 0.05) at 12 h after rCgWnt-1 treatment. When the Wnt signal inhibitor C59 was injected simultaneously with rCgWnt-1, the expressions of Cg8-catenin, CgRunx-1, and CgCDK2 were significantly reduced, which were 0.32-fold (p < 0.05), 0.16-fold (p < 0.05), and 0.25-fold (p < 0.05) of that in rCgWnt-1 group, respectively, and the percentage of EDU+ cells in haemocytes was also significantly inhibited (0.15-fold compared with that in rCgWnt-1 group, p < 0.05). These results suggested that the conserved CgWnt-1 could modulate haemocytes proliferation via regulating cell cycle related genes and involved in the immune response of oysters.

Automated summary

Recent findings show that Wnt signaling plays an important role in regulating the differentiation and proliferation of immune cells. In this study, a Wnt-1 homolog (CgWnt-1) was identified from oyster Crassostrea gigas, and its mRNA expression was found to be significantly up-regulated during the later stages of embryonic development. CgWnt-1 was highly expressed in the mantle of adult oyster. After stimulation with Vibrio splendidus, the mRNA expression levels of CgWnt-1 and Cg8-catenin in haemocytes were significantly increased. Injection of recombinant protein (rCgWnt-1) into oyster resulted in the up-regulation of cell proliferation related genes and an increase in the percentage of proliferating cells in haemocytes. The inhibitory effect of the Wnt signal inhibitor C59 on these responses was also demonstrated. These results indicate that CgWnt-1 plays a role in modulating haemocyte proliferation and immune response in oysters.