Cloning and characterization of a cDNA encoding walleye (Sander vitreum) beta-2 microglobulin

Beta2-microglobulin (β2m) is an essential component of the MHC class I antigen presentation pathway, necessary for heavy chain folding and peptide binding. In this study a β2m cDNA isolated from a walleye head kidney library was sequenced and found to be similar to other known β2m sequences. The clone encodes a predicted protein sequence of 116 residues, with a mature peptide 100 amino acids in length. This represents an inconsistency with other predicted β2m protein sequences as walleye contains an additional 3 residues at the N terminus of the mature protein. Southern blot analysis showed that β2m is present in one copy in the walleye genome and northern blot analysis showed expression of a 1.2 Kb transcript, with high expression in kidney, spleen, gills and intestine. Characterization of this gene will enable further studies of immune function in walleye, which comprises both an important fishery and an emerging aquaculture species in Canada.