TY - JOUR TI - Widespread discrepancy in Nnt genotypes and genetic backgrounds complicates granzyme A and other knockout mouse studies AU - Rawle, Daniel J AU - Le, Thuy T AU - Dumenil, Troy AU - Bishop, Cameron AU - Yan, Kexin AU - Nakayama, Eri AU - Bird, Phillip I AU - Suhrbier, Andreas A2 - Takayanagi, Hiroshi A2 - Isales, Carlos VL - 11 PY - 2022 DA - 2022/02/04 SP - e70207 C1 - eLife 2022;11:e70207 DO - 10.7554/eLife.70207 UR - https://doi.org/10.7554/eLife.70207 AB - Granzyme A (GZMA) is a serine protease secreted by cytotoxic lymphocytes, with Gzma-/- mouse studies having informed our understanding of GZMA’s physiological function. We show herein that Gzma-/- mice have a mixed C57BL/6J and C57BL/6N genetic background and retain the full-length nicotinamide nucleotide transhydrogenase (Nnt) gene, whereas Nnt is truncated in C57BL/6J mice. Chikungunya viral arthritis was substantially ameliorated in Gzma-/- mice; however, the presence of Nnt and the C57BL/6N background, rather than loss of GZMA expression, was responsible for this phenotype. A new CRISPR active site mutant C57BL/6J GzmaS211A mouse provided the first insights into GZMA’s bioactivity free of background issues, with circulating proteolytically active GZMA promoting immune-stimulating and pro-inflammatory signatures. Remarkably, k-mer mining of the Sequence Read Archive illustrated that ≈27% of Run Accessions and ≈38% of BioProjects listing C57BL/6J as the mouse strain had Nnt sequencing reads inconsistent with a C57BL/6J genetic background. Nnt and C57BL/6N background issues have clearly complicated our understanding of GZMA and may similarly have influenced studies across a broad range of fields. KW - granzyme A KW - nicotinamide nucleotide transhydrogenase KW - chikungunya KW - inflammation KW - C57BL/6J KW - C57BL/6N JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -