Molecular characterization and expression analysis of the TRAF gene family in the fourfinger threadfin (Eleutheronema tetradactylum)

Abstract

Originally characterized as adapter proteins linking TNF receptors to downstream signaling cascades, tumor necrosis factor receptor-associated factors (TRAFs) have since been recognized as pivotal signal transducers for multiple receptor families, regulating diverse biological processes. To date, seven mammalian TRAF members (TRAF1-7) have been identified, with well-documented roles in mediating innate immune responses. However, the functional significance of TRAFs in the innate immunity of the fourfinger threadfin (Eleutheronema tetradactylum) remains poorly understood. In this study, we identified and characterized eight TRAF genes in E. tetradactylum, designated EtTRAF2a, EtTRAF2b, EtTRAF2-like, EtTRAF3, EtTRAF4a, EtTRAF5, EtTRAF6, and EtTRAF7. Comprehensive sequence analysis revealed structural features conserved, including a C-terminal MATH domain and an N-terminal RING domain in all EtTRAFs, whereas EtTRAF7 uniquely contained seven WD40 repeat domains in its C-terminal region. Tissue distribution profiling via quantitative real-time PCR (qPCR) demonstrated constitutive expression of all eight EtTRAF genes across eight healthy tissues (skin, liver, brain, gill, spleen, kidney, heart, and intestine), with notably higher transcript levels in the liver and gill. Furthermore, the lipopolysaccharide (LPS) challenge induced significant temporal modulation of EtTRAF expression patterns. Collectively, our systematic investigation of TRAFs in E. tetradactylum provides critical insights into their putative roles in innate immune defense against pathogens and establishes a framework for future functional studies on TRAF-mediated signaling in teleost fishes.