IGFBP7 promotes hemocyte proliferation in small abalone Haliotis diversicolor, proved by dsRNA and cap mRNA exposure

Insulin-like growth factor binding protein 7 (IGFBP7) binds IGFs with a low affinity, but in contrast, recognizes insulin with a high affinity. Many studies show that IGFBP7 involves several cellular processes of vertebrates and functions as a tumor suppressor gene in different tumors. However, the function of IGFBP7 in invertebrates is unclear. In this research, we studied the function of IGFBP7 in the proliferation of small abalone Haliotis diversicolor hemocytes by exposure to dsRNA or cap mRNA of saIGFBP7. We found that exposure to dsRNA or cap mRNA of saIGFBP7 could significantly affect the mRNA and protein expression of IGFBP7 in cultured small abalone hemocytes (p<0.05). There was a significant increase in hemocyte density and the number of adherent hemocytes after exposure to cap mRNA of saIGFBP7 (p<0.05). Similarly, exposure to dsRNA of saIGFBP7 could significantly decrease the hemocyte density and the number of adherent hemocytes (p<0.05). These findings suggest that IGFBP7 increases hemocyte growth. It is the first time to report the effect of IGFBP7 on the proliferation of marine invertebrate cells.