New Lyz1-CreERT2 Mouse Enables Paneth Cell Studies

Overview of Lysozyme and Its Role

Lysozyme is a critical antimicrobial enzyme widely found in animals, plants, and microorganisms. It protects the host through its bactericidal effect of hydrolyzing the glycosidic bonds in bacterial cell walls, making it an essential component of the body's defense system. The genes encoding lysozyme—and its expression patterns—vary between species. Humans possess a single lysozyme gene (LYZ), while mice have two genes (Lyz1 and Lyz2). The mouse genes are expressed in different cell types, with Lyz1 primarily in Paneth cells and Lyz2 in leukocytes. ^[1]

In mice, the Lyz1 gene encodes lysozyme C, which is primarily expressed in Paneth cells located in the small intestine. Variations in Paneth cells and abnormal lysozyme production are hallmarks of inflammatory bowel disease (IBD) pathology. Studies have shown that targeted deletion of lysozyme C in Paneth cells (Lyz1) protects mice from experimentally induced colitis. The absence of the Lyz1 gene weakens the immune response to bacterial molecular patterns in the gut, leading to the expansion & overgrowth of lysozyme-sensitive mucolytic bacteria—highlighting its role in gut homeostasis.^[2]

Lyz1-H2BmCherry-lRES-CreERT2 Mouse Model

To address research needs for specific investigations into Paneth cells, Cyagen has developed the Lyz1-H2BmCherry-IRES-CreERT2 mouse model (Product ID: C001567) using gene-editing techniques. This model integrates the H2BmCherry-IRES-CreERT2 cassette into the mouse Lyz1 gene locus, disrupting the endogenous Lyz1 gene expression in mice while driving the specific expression of the inserted components.

When Lyz1-H2BmCherry-IRES-CreERT2 mice are crossed with mice containing loxP sites, tamoxifen-induction on offspring results in recombination between loxP sites mediated by Cre recombinase in the small intestinal Paneth cells. Additionally, this model carries a red fluorescent protein (H2BmCherry) expression element, which can be used for lineage tracing of Lyz1-positive cells.

• CreERT2 recombinase: In the absence of tamoxifen, the CreERT2 recombinase is localized in the cytoplasm. After tamoxifen treatment, CreERT2 recombinase translocates to the nucleus to exert its recombination activity.
  ○ Note: Requires breeding with mice containing loxP sites.
• H2BmCherry fluorescent protein: Facilitates lineage tracing of Lyz1-positive cells.

Due to the inducible functionality of CreERT2, the Lyz1-H2BmCherry-IRES-CreERT2 mouse model may be used to generate both the control and study groups by breeding with loxP mice.

Validation of Cre Recombinase Activity in Paneth Cells

To confirm the specificity and functionality of Cre activity in Paneth cells, Lyz1-H2BmCherry-IRES-CreERT2 mice were crossed with Rosa26-LSL-tdTomato mice, which conditionally express tdTomato fluorescent protein. We evaluated the successful Cre recombinase-mediated deletion of the STOP cassette (LSL) results in tdTomato fluorescence expression in Cre-positive cells as below.

1. Tamoxifen Induction: Eight-week-old offspring were treated with tamoxifen, activating Cre recombinase.
2. Tissue Analysis: Ileal tissues were collected post-induction, cryosectioned, and observed for spontaneous fluorescence.
3. Results: Histological analysis revealed distinct tdTomato fluorescence was detected at the base of intestinal crypts in Paneth cells of Cre+TAM+ mice, confirming Cre-mediated recombination in Lyz1-positive cells.

Conclusion: Key Mouse Model for Research

The Lyz1-H2BmCherry-IRES-CreERT2 mouse model (Product ID: C001567) provides a robust platform for studying Paneth cell-specific gene expression and its role in intestinal immunity and disease. Due to the inducible functionality of CreERT2, the Lyz1-H2BmCherry-IRES-CreERT2 mouse model may be used to generate both the control and study groups by breeding with loxP mice.

Key Applications

This model can be used for tissue-specific studies targeting small intestinal Paneth cells and is particularly valuable for research in:

• Inflammatory bowel diseases (IBD), including Crohn’s disease and ulcerative colitis
• Host-microbiota interactions
• Intestinal inflammation and regeneration

Explore More from Cyagen’s Cre Mouse Line Library

Cyagen offers a comprehensive range of Cre and inducible CreERT2 mouse models tailored for targeted tissue-specific research, including:

• Adipoq-iCre Mice: Targeting adipose tissues
• Col1a2-iCre Mice: Specific to fibroblasts
• MerCreMer and CreERT2 Comparison: Detailed insights into inducible Cre systems
• ApoE KO Mice: Ideal for atherosclerosis studies
• NASH Mouse Models: HFD+CCl4-induced metabolic dysfunction research

References

[1] Markart P, Faust N, Graf T, Na CL, Weaver TE, Akinbi HT. Comparison of the microbicidal and muramidase activities of mouse lysozyme M and P. Biochem J. 2004 Jun 1;380(Pt 2):385-92./p>

[2] Yu S, Balasubramanian I, Laubitz D, Tong K, Bandyopadhyay S, Lin X, Flores J, Singh R, Liu Y, Macazana C, Zhao Y, Béguet-Crespel F, Patil K, Midura-Kiela MT, Wang D, Yap GS, Ferraris RP, Wei Z, Bonder EM, Häggblom MM, Zhang L, Douard V, Verzi MP, Cadwell K, Kiela PR, Gao N. Paneth Cell-Derived Lysozyme Defines the Composition of Mucolytic Microbiota and the Inflammatory Tone of the Intestine. Immunity. 2020 Aug 18;53(2):398-416.e8.