Lyz2-IRES-CreERT2 Mouse

Lysozyme, encoded by the LYZ gene, is an integral component of the innate immune system. Its primary function is to disrupt bacterial cell walls by cleaving the β-1,4-glycosidic bond between N-acetylmuramic acid and N-acetylglucosamine in bacterial peptidoglycan, leading to bacterial lysis. Lysozyme is abundant in various secretions, including tears, saliva, human milk, and mucus, as well as in the cytoplasmic granules of macrophages and polymorphonuclear neutrophils. Cytoplasmic lysozyme expression is high in bone marrow cells, Paneth cells, and a subset of salivary gland cells ^[1-2].

Mice have two lysozyme-encoding genes, Lyz1 and Lyz2, which are highly homologous to the human LYZ gene. Lyz1 is primarily expressed in Paneth cells, while Lyz2 is mainly expressed in myeloid cells. Myeloid-specific expression of Lyz2 is associated with cell-type-specific demethylation of its downstream enhancer. The Lyz2 protein also has lysozyme activity and participates in defense responses against both Gram-negative and Gram-positive bacteria. Lyz2 is expressed in the hematopoietic system, liver, mesothelium, small intestine, and yolk sac of mice ^[3-4].

Lyz2-IRES-CreERT2 mice were generated using gene editing technology to integrate the tamoxifen-inducible CreERT2 recombinase expression element into the 3’UTR of the mouse Lyz2 gene. This mimics the expression pattern of the endogenous gene while maintaining Lyz2 expression. When bred with mice carrying a loxP site-flanked sequence, Cre recombinase-mediated recombination of the flanked sequence occurs in myeloid cells, including monocytes, mature macrophages, and granulocytes, following tamoxifen induction.