Genetic variant in 3' untranslated region of the mouse pycard gene regulates inflammasome activity

Quantitative trait locus mapping for interleukin-1β release after inflammasome priming and activation was performed on bone-marrow-derived macrophages (BMDM) from an AKRxDBA/2 mouse strain intercross. The strongest associated locus mapped very close to the gene on chromosome 7, which codes for the inflammasome adaptor protein apoptosis-associated speck-like protein containing a CARD (ASC). The DBA/2 and AKR genes only differ at a single-nucleotide polymorphism (SNP) in their 3' untranslated region (UTR). DBA/2 vs. AKR BMDM had increased levels of mRNA expression and ASC protein, and increased inflammasome speck formation, which was associated with increased mRNA stability without an increased transcription rate. CRISPR/Cas9 gene editing was performed on DBA/2 embryonic stem cells to change the 3'UTR SNP from the DBA/2 to the AKR allele. This single base change significantly reduced expression and inflammasome activity after cells were differentiated into macrophages due to reduced mRNA stability.