Molecular characterizing and expression analysis of MCSF and its receptor in largemouth bass (Micropterus salmoides) and spotted sea bass (Lateolabrax maculatus).

Macrophage colony-stimulating factor (MCSF) is a key hematopoietic cytokine that regulates the proliferation, differentiation, and survival of mononuclear phagocytes through its receptor, MCSFR. In this study, we cloned and characterized the full-length cDNAs encoding MCSF and MCSFR from two commercially important perciform fish, largemouth bass (Micropterus salmoides) and spotted sea bass (Lateolabrax maculatus). The largemouth bass MCSF (MsMCSF) cDNA contains a 792-bp open reading frame (ORF) encoding 263 amino acids, whereas the spotted sea bass MCSF (LmMCSF) cDNA has an 813-bp ORF encoding 270 amino acids. Both MsMCSF and LmMCSF possess a signal peptide, a conserved CSF-1 domain, three cysteine residues required for homodimerization, and a transmembrane region. The corresponding MCSFR cDNAs encode proteins of 1050 (MsMCSFR) and 1025 (LmMCSFR) amino acids, each featuring a signal peptide, four immunoglobulin-like domains, and an intracellular tyrosine kinase domain. Phylogenetic analysis revealed that both MCSF and MCSFR cluster with their teleost counterparts, respectively. Tissue distribution profiling showed that MCSF and MCSFR transcripts are most abundant in the immune-related tissues, especially the headkidney (HK) and spleen. Upon challenge with Poly(I:C), Edwardsiella tarda, or Nocardia seriolae in largemouth bass, and with LPS, Poly(I:C), or E. tarda in spotted sea bass, all the four genes exhibited significant and tissue-specific transcriptional modulation from 6 to 48 h post-injection, suggesting that they may participate in the antiviral and antibacterial immune responses of largemouth bass and spotted sea bass. These results provide a basis for further functional studies on the immunoregulatory roles of MCSF/MCSFR signaling in teleost.