Phenotypic Evaluation of TREX1 Null Mice as a Model for Lupus-Like Autoimmune Disease

Abstract

Abstract TREX1 (DNase III) is the major mammalian 3’-5’ DNA exonuclease and thought to play a major role in cell death and genomic DNA degradation. Dysfunction of Trex1 has been suggested to activate immune response by self DNA, as TREX1 null mice develop inflammatory myocarditis similar to autoimmune cardiomyopathy and produce type 1 IFN. TREX1 D18N causes a monogenic cutaneous form of lupus called familial chilblain lupus and exhibits dysfunctioned dsDNA-degrading activity, providing a link between dsDNA degradation and nucleic acid-mediated autoimmune diseases. Using CRISPR-Cas9, we generated a Trex1 −/−mouse by knocking out exon 2 and performed comprehensive phenotypic analyses to evaluate the loss of function of TREX1 and its potential application in SLE research. Both female and male TREX1 null mice showed dramatically increased post-wean morbidity and significantly increased serum ALT, AST and LDH levels, compared to wildtype and heterozygotes from 6 to 24 weeks of age, indicating liver and heart injuries. Pathohistological analysis showed inflammatory immune cell infiltration in liver, heart, spleen, kidney, lung and skin among TREX1 null mice. Serum anti-dsDNA antibody levels were significantly increased and remained high from 7 to 25 weeks of age, consistent with Trex1’s being the major DNA exonuclease. Urine protein to creatinine ratio was dramatically increased at 28 weeks of age among TREX1 null mice. In conclusion, the Trex1 −/−mice we generated in this work showed lupus-like inflammatory autoimmune responses in multiple organs, providing an urgently needed tool to study Trex1-mediated autoimmunity and to evaluate potential therapeutic treatments for lupus.