DNA-binding protein Ikaros is a major determinant of haematopoietic lineage, especially in the development, differentiation and proliferation of lymphocytes. In the present study, a Ikaros homologue (designed as CgIkaros-like) was identified and characterized as a vital determinant in the proliferation of haemocytes during haematopoiesis of Pacific oyster Crassostrea gigas. The complete coding sequence of CgIkaros-like was of 1329 bp encoding a predicted polypeptide of 442 amino acids with four ZnF regions, locating at the C-terminus and N-terminus respectively. The highest expression level of CgIkaros-like mRNA was found in gills, followed by haemocytes and gonad. The mRNA transcripts of CgIkaros-like could be detected in all the haemocytes with higher abundance in semi-granulocytes and agranulocytes. CgIkaros-like protein was localized in both of cytoplasm and nucleus with higher abundance in nucleus of oyster haemocytes. The mRNA and protein expression levels of agranulocyte marker CgCD9, granulocyte marker CgAATase, cell cycle related gene CgCDK2, Notch receptor CgNotch and Notch target gene CgHes1 all increased significantly (p < 0.05) after CgIkaros-like was interfered by siRNAs, which were about 27.33-, 2.63-, 24.34-, 4.45- and 6.08-fold of that in the siRNA-NC control group, respectively. While the transcripts of CgGATA3 and CgRunx did not change significantly after CgIkaros-like was interfered. These results demonstrated that CgIkaros-like functioned as a transcription factor combined with Notch pathway to mediate CgCDK2 and regulate the proliferation of oyster haemocytes.

DNA 结合蛋白 Ikaros 是造血谱系的主要决定因素，特别是在淋巴细胞的发育、分化和增殖中。在本研究中，Ikaros 同源物（设计为Cg Ikaros 样）被鉴定并表征为太平洋牡蛎巨牡蛎造血过程中血细胞增殖的重要决定因素。Cg Ikaros-like的完整编码序列为1329 bp，编码442个氨基酸的预测多肽，具有四个ZnF区，分别位于C端和N端。Cg Ikaros-like mRNA在鳃中的表达水平最高，其次是血细胞和性腺。Cg的 mRNA 转录本在半粒细胞和粒细胞中丰度较高的所有血细胞中均可检测到Ikaros样。Cg Ikaros样蛋白定位于细胞质和细胞核中，牡蛎血细胞细胞核中丰度较高。Cg后粒细胞标志物Cg CD9、粒细胞标志物Cg AATase、细胞周期相关基因Cg CDK2、Notch 受体Cg Notch 和 Notch 靶基因Cg Hes1的 mRNA 和蛋白表达水平均显着升高（ p  < 0.05）Ikaros-like受到siRNA的干扰，分别是siRNA-NC对照组的27.33-、2.63-、24.34-、4.45-和6.08-倍。而Cg Ikaros-like 干扰后Cg GATA3 和Cg Runx的转录本没有明显变化。这些结果表明，Cg Ikaros-like 作为转录因子与 Notch 途径相结合，介导Cg CDK2 并调节牡蛎血细胞的增殖。