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INCREASED CIRCULATING PLASMA MANNOSE BINDING LECTIN ASSOCIATED SERINE PROTEASE (MASP) AS A RESULT OF ENU-INDUCED MUTATION IN MASP-1

Aim: The study of immune responses in animal models has been paramount in guiding current understanding of human immune function. N-ethyl-N-nitrosourea (ENU) is a chemical mutagen that introduces a high rate of random point mutations into the mouse germline. ENU directed mutagenesis resulted in a C-T base change, (amino acid 550, E→K) in exon 13 of mannose-binding lectin associated serine protease (MASP) 1. MASP-1ENU mice were studied to assess changes in free MASP and other blood parameters. Methods: MASP-1 level was determined by ELISA (USCN Life Science) and blood physiology compared between affected and unaffected mice (unpaired T test, 95%CI). Differential blood count (RBC, platelet, neutrophil lymphocyte, monocyte, eosinophil, basophil, reticulocytes) and haematological parameters (haemoglobin, haematocrit, mean cell volume) were assessed (ADVIA). Results: The MASP-1ENU pedigree was viable. Both heterozygous and homozygous MASP-1ENU mice demonstrated significantly elevated levels of free MASP-1 in circulation (p < 0.05 for both heterozygotes and homozygotes compared to unaffected). Mutation in MASP-1 did not result in changes in any of the other blood parameters studied. Conclusions: The novel ENU-induced MASP-1 mutation resulted in increased circulating plasma MASP suggesting mutation in the peptidase-S1A region of MASP-1 may impact on binding of MASP to MBL. Dissociation of MASP/MBL may result in alterations in important MASP dependant pathways including complement and coagulation.