Molecular structure, expression pattern and functional characterisation of APRIL in an aquatic mammal

The Yangtze finless porpoise (Neophocaena phocaenoides asiaorientalis) is listed on the First Order of Protected Animals in China and was identified as an endangered species by the International Union for Conservation of Nature and Natural Resources (IUCN) in 2011. A proliferation inducing ligand (APRIL), belonging to the tumour necrosis factor (TNF) family, is critical for immune regulation. In this study, we identified a finless porpoise APRIL cDNA (fAPRIL) by RACE (rapid amplification of cDNA ends) strategies, from the Yangtze finless porpoise (fAPRIL). This gene encodes 247 amino acids containing a predicted transmembrane domain and a TNF domain, and phylogenetic analysis of the APRIL sequence indicated that finless porpoises are closely related to Artiodactyla. In vitro, soluble fAPRIL (fsAPRIL) not only promoted the survival/proliferation of the mouse spleen lymphocytes, but also bound specifically to the surface of the B cells. The results of this study contribute to our understanding of the immune mechanisms in the finless porpoise and other aquatic mammals.