Uccellini, M.B. et al. Cell Rep. 31, 107498 (2020)

Through studies of knockout mice, the protein sterile alpha and TIR motif containing 1 (SARM1) has been ascribed roles in mediating axon degeneration and in the susceptibility of the nervous system to various viral infections, including West Nile, La Cross encephalitis, and vesicular stomatitis. The mice used for much of that work were generated by knocking out Sarm1 in 129 embryonic stem cells and crossing those onto a C57BL/6 background. Those strain choices, however, may have been a bit confounding.

Using CRISPR, researchers at the Icahn School of Medicine at Mt. Sinai recently created SARM1-deficient mice on a pure black 6 background. The gene’s potential role in axon degeneration and West Nile Virus susceptibility held true, but many other immune-related phenotypes observed in the classic knockout animals were absent. Background beware.