Widespread discrepancy ingenotypes and genetic backgrounds complicates granzyme A and other knockout mouse studies.

Abstract

Granzyme A (GZMA) is a serine protease secreted by cytotoxic lymphocytes, withmouse studies having informed our understanding of GZMA's physiological function. We show herein thatmice have a mixed C57BL/6J and C57BL/6N genetic background and retain the full-length nicotinamide nucleotide transhydrogenase () gene, whereasis truncated in C57BL/6J mice. Chikungunya viral arthritis was substantially ameliorated inmice; however, the presence ofand the C57BL/6N background, rather than loss of GZMA expression, was responsible for this phenotype. A new CRISPR active site mutant C57BL/6Jmouse 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 hadsequencing reads inconsistent with a C57BL/6J genetic background.and C57BL/6N background issues have clearly complicated our understanding of GZMA and may similarly have influenced studies across a broad range of fields.