Characterization of MACPF domain containing proteins in oyster Crassostrea gigas and their expression profile in response to immune stimulation

• Ten Cg MACPFs share highly conserved MACPF domains were identified in oyster genome. • Cg MACPFs were classified into MPEG1 (Macrophage-expressed gene 1) and PRF1 (Perforin-1) subfamily. • Cg MACPFs in MPEG1 subfamily functioned in embryonic development and were responsive for immune stimulation. • Cg MACPFs in PRF1 subfamily (especially Cg MACPF-7/8) were involved in immune priming response of oyster. Membrane attack complex/perforin (MACPF) domain containing proteins play crucial roles in the immune systems of various organisms, but their identification, classification and functions in oysters remain largely unknown. This study screened the MACPF domain containing proteins in the genome of oyster Crassostrea gigas , to identify and characterize MACPF containing proteins as well as explore their role in immune priming. In C. gigas , ten Cg MACPFs with highly conserved MACPF domains were identified in the oyster genome, and their genes were distributed in four chromosomes. Among these, Cg MACPF-1-7 contained only the MACPF domain and Cg MACPF-8/9/10 all contained an additional ApeC domain. A search on MEME program identified 12 conserved motifs in Cg MACPFs, with Cg MACPF-1-5 contained more conserved motif compared with those in Cg MACPF-6-10. Based on the phylogenetic analysis with MACPF proteins in other species and structure characteristics, Cg MACPF1-5 were classified into MPEG1 subfamily and Cg MACPF6-10 in Perforin-1 subfamily. By examining their expression patter during embryonic development and in response to immune stimulation, Cg MACPFs in MPEG1 subfamily was found to functioning in embryonic development and were responsive for immune stimulation. And Cg MACPFs in PRF1 subfamily (especially Cg MACPF-7/8) were involved in immune priming response of oyster. This research characterized the two subfamilies of MACPF domain containing proteins in oyster, and also determined their responsiveness to immune stimulation and involvement in immune priming, which can expand our understanding of MACPF containing proteins in invertebrate immunology.