WNT9A is a secreted ligand that activates both canonical Wnt/β-catenin and non-canonical Wnt signaling pathways through binding to frizzled receptors 1. The protein functions as a critical regulator of cellular senescence and tissue fibrosis, particularly in renal disease, where elevated WNT9A expression promotes tubular epithelial cell senescence through upregulation of p16INK4A, p53, and p21, ultimately driving renal fibrosis progression 2. In cancer contexts, WNT9A variants contribute to hepatocellular carcinoma risk stratification in cirrhotic patients 3 and mediate neuroendocrine differentiation in prostate cancer through non-canonical FZD8/FYN/STAT3 pathway activation 4. During development, WNT9A exhibits asymmetric expression patterns that control cell fate specification, particularly in cochlear development where it influences hair cell differentiation and neural connectivity across the radial axis 5. In wound healing, WNT9A promotes fibroblast migration and collagen remodeling through non-canonical Wnt signaling pathways 6. Additionally, WNT9A genetic variants are associated with late-onset acute respiratory distress syndrome and patient survival outcomes 7. The protein demonstrates high evolutionary conservation among mammalian orthologs, though promoter regions show significant divergence 8.