Regulatory role of ETS1 transcription factor in hemocytes proliferation in Anadara granosa

Abstract

The ETS1 transcription factor is crucial in the process of biological development. In vertebrate, ETS1 plays a pivotal role in promoting endothelial cell proliferation and angiogenesis. However, the identity and function of ETS1 remains unclear in mollusks. In this study, an ETS1 homolog (named as AgETS1) was identified in blood clam Anadara granosa (synonym: Tegillarca granosa). The full length of the AgETS1 transcription factor is 1569 bp, consisting of 539 amino acids, including the Sterile Alpha Motif (SAM) domain, which can recognize and bind to sequence of GGAA. Tissue expression analysis of A. granosa showed that AgETS1 exhibits the highest expression level in the gill tissues (51.5-fold of that in hemocyte, p < 0.05). AgETS1 mRNA transcripts were predominantly expressed during larval development, from zygote to trochophore stage. Moreover, the expression levels of AgETS1 in blood clams with high hemoglobin concentration (hemocyte count >1.75 × 108 cells/mL) were significantly higher than that in blood clams with low hemoglobin concentration (hemocyte count <8.5 × 107 cells/mL) (p < 0.05). RNA interfering (RNAi) of AgETS1 induced a corresponding decrease in the number of hemocytes in the hemolymph and a reduction in EdU-marked proliferating cells in the gill tissue. These results indicated that the ETS1 actively regulated the proliferation of hemocytes in A. granosa.