Molecular characterization and expression dynamics of Labeo rohita MDA5, its adaptor MAVS and pro-inflammatory...

Melanoma differentiation-associated gene 5 (MDA5) is a prime member of the RIG-I-like receptor (RLR) family that recognises viral RNA in the cytoplasm and triggers antiviral innate immunity mainly via the MAVS-dependent signalling cascade. This study reports the molecular cloning and characterization of MDA5 in Labeo rohita (LrMDA5), a commercially important major carp in India and Southeast Asia. The LrMDA5 has 3000bp open reading frame (ORF) encoding a 1000-amino acid protein of molecular weight (mw) 240.764 kDa and isoelectric point (pI) of ∼4.84. It's structural domain analysis identified two CARDs, a DEXDc, a helicase, and a C-terminal domain. Phylogenetically, LrMDA5 is closest to the Cyprinus carpio, and the ontogenic expression profiling revealed maximal expression at neurula stage {12h post-fertilization (h.p.f)}. It was ubiquitously expressed across all tested organs/tissues, and in specialised cells such as mucosal RBCs (red blood cells) and PBLs (peripheral blood leukocytes). LrMDA5 gene transcripts along with its adaptor molecule, MAVS, and the cytokines (IL-8 and IL-1β) gene expression were significantly upregulated both in-vivo and in-vitro against poly I:C and LPS-stimulations, and infections with Aeromonas hydrophila and Edwardsiella tarda. These data together highlight the important immune role of MDA5 in fish.