Psoriasis 2 (PSORS2) Cell Models for Research

Psoriasis is a chronic inflammatory skin disease affecting approximately 2-3% of the global population, with significant variation across regions (WHO, 2023). The disease imposes a substantial burden on quality of life and is associated with comorbidities such as cardiovascular disease, metabolic syndrome, and depression. Psoriasis 2 (PSORS2) is a genetic subtype characterized by familial inheritance and early onset. While not directly lethal, severe cases can lead to disability and increased mortality risk due to associated complications. The clinical impact is profound, with many patients requiring long-term systemic therapy. Research into PSORS2 is essential to develop targeted therapies that address the underlying genetic causes.

PSORS2 serves as an excellent model for studying the molecular mechanisms of psoriasis because it has a well-defined genetic basis, primarily involving mutations in the CARD14 gene. This allows for the creation of precise gene-edited cell models that recapitulate the disease phenotype. Public datasets, such as those from the Genotype-Tissue Expression (GTEx) project and the Human Cell Atlas, provide valuable resources for studying gene expression in relevant cell types. Open questions include the exact signaling pathways downstream of CARD14 and the interplay between keratinocytes and immune cells. Gene-edited models are invaluable for addressing these questions and for drug discovery.

Psoriasis is not a cancer, but it involves dysregulated cell proliferation and inflammation. The major pathways implicated in PSORS2 include:

• • NF-κB signaling: CARD14 mutations lead to constitutive activation of NF-κB, promoting inflammation and keratinocyte proliferation.
• • MAPK/ERK pathway: Activation of this pathway contributes to abnormal keratinocyte differentiation and proliferation.
• • JAK-STAT pathway: Cytokine signaling through JAK-STAT is enhanced, leading to chronic inflammation.
• • IL-23/Th17 axis: This immune pathway is central to psoriasis pathogenesis, with IL-23 promoting Th17 cell differentiation and IL-17 production.

Data from COSMIC and ClinVar.

The key deregulated networks in PSORS2 include:

• • NF-κB signaling: Central node, activated by CARD14 mutations, leading to pro-inflammatory cytokine production.
• • MAPK cascade: Involves RAS, RAF, MEK, ERK; contributes to keratinocyte hyperproliferation.
• • PI3K/AKT pathway: Promotes cell survival and proliferation.
• • JAK-STAT pathway: Mediates cytokine signaling, particularly IL-6, IL-22, and IL-23.
• • IL-23/Th17 axis: Key driver of psoriatic inflammation.

These networks interact to create a chronic inflammatory loop.

Organoids derived from patient biopsies or gene-edited keratinocytes offer a more physiologically relevant 3D model, allowing study of cell-cell interactions and drug responses.

• • PDX models: Patient-derived xenografts of psoriatic skin into immunodeficient mice, preserving the human disease phenotype.
• • GEMM (Genetically Engineered Mouse Models): Mice with inducible CARD14 mutations (e.g., CARD14E138A) that develop psoriasiform dermatitis.
• • Induced models: Imiquimod-induced psoriasis-like skin inflammation in mice, commonly used for drug testing.
• • Xenograft models: Injection of gene-edited keratinocytes into mice to study tumorigenesis (though psoriasis is not cancer).

CRISPR-Cas9 technology enables the creation of isogenic cell lines with precise genetic modifications. For PSORS2, we offer:

• • CARD14 knockout cell lines: Inactivate CARD14 to study loss-of-function effects.
• • CARD14 point-mutation knock-in lines: Introduce specific gain-of-function mutations (e.g., p.Gly117Ser) to mimic patient variants.
• • Reporter lines: GFP or luciferase under the control of NF-κB response elements to monitor pathway activation.

These models are sequence-verified and available from commercial sources, accelerating research by providing consistent, reproducible tools.

Gene-edited cells are used to validate the functional impact of genetic variants. For example, CARD14 knockout in keratinocytes reduces NF-κB activation and inflammatory cytokine production, confirming its role. Knock-in of disease-associated mutations can recapitulate the hyperinflammatory phenotype, enabling downstream mechanistic studies.

Isogenic pairs (wild-type vs. mutant) are ideal for high-throughput screening of compounds that specifically inhibit the mutant phenotype. For instance, screening for inhibitors of NF-κB signaling in CARD14-mutant cells can identify potential therapeutics. Resistance mechanisms can be studied by chronic exposure to drugs and analyzing adaptive changes.

CRISPR-based synthetic lethality screens can identify genes that, when knocked out, are lethal only in the context of CARD14 mutations. This can reveal novel therapeutic targets and biomarkers. Additionally, secretome analysis of gene-edited cells can identify soluble factors that serve as biomarkers for disease activity.