Parkinson, J. E.; Baldwin, G. E.; Papotto, P. H.; Humphreys, N. E.; Adamson, A. D.; Allen, J. E.; Sutherland, T. E.

Chitinase-like proteins (CLPs) are of wide interest due to their significant roles during both biological and pathological processes. Human CLPs such as YKL-40 have been suggested as biomarkers of disease severity in many conditions. Murine CLPs include Brp39, Ym1, and Ym2 and these are similarly upregulated in multiple mouse models of pathology. Investigation of these molecules, particularly Ym1 and Ym2, is plagued by complexity in the genomic locus due to recent gene duplication events in the C57BL/6 strain. Using a novel CRISPR-Cas9 targeting approach involving CB6 mixed background embryos, we generated a Ym1 deficient mouse. Validation using flow cytometry, ELISA, and immunofluorescence confirmed no expression of mature Ym1 protein with no alteration in the expression of related chitinases/CLP genes including Chia and Chil4. This new transgenic mouse line will be key for investigating CLP functions and the genetic approach utilised may provide a useful strategy for other genes which show differences between inbred mouse strains.