JAK Activation Drives MED15-Associated Melanocyte Dysfunction in Vitiligo Beyond Immune Cells

Area of Science:

• Dermatology
• Genetics
• Immunology

Background:

• Vitiligo is an autoimmune disorder causing melanocyte loss, driven by interferon-gamma (IFN-γ)-induced Janus kinase/signal transducers and activators of transcription (JAK-STAT) pathway activation.
• The precise downstream transcriptional mediators within melanocytes affected by JAK-STAT signaling in vitiligo are not fully understood.

Purpose of the Study:

• To identify causal JAK-responsive genes associated with vitiligo by integrating multi-omics data and functional assays.
• To elucidate the role of identified genes in melanocyte dysfunction and vitiligo pathogenesis.

Main Methods:

• Integrated multi-omics analyses including GWAS, TWAS, COJO, and SMR with 391 vitiligo cases and 465,673 controls.
• Single-cell RNA sequencing (scRNA-seq) of vitiligo lesions and healthy controls.
• In vitro functional assays and dual-luciferase reporter assays to validate gene function and regulatory relationships.

Main Results:

• Mediator complex subunit 15 (MED15) was identified as a gene significantly associated with increased vitiligo risk.
• MED15 was upregulated in melanocytes from vitiligo lesions, correlating with STAT1 expression and JAK-STAT pathway activity.
• MED15 overexpression inhibited melanocyte proliferation and melanin synthesis, effects reversed by JAK inhibition; MED15 is a direct STAT1 transcriptional target.

Conclusions:

• MED15 acts as a JAK-responsive cofactor, impairing melanocyte proliferation and melanogenesis in vitiligo.
• A direct STAT1-MED15 transcriptional axis contributes to melanocyte injury in vitiligo.
• MED15 represents a potential therapeutic target for vitiligo, complementary to JAK inhibition.