KIRREL1 is a transmembrane cell adhesion molecule essential for glomerular filtration barrier integrity. Structurally, it belongs to the slit diaphragm protein family and contains immunoglobulin domains with conserved intrinsically unstructured regions 1. Functionally, KIRREL1 maintains stable podocyte architecture by connecting interdigitating foot processes through specialized slit diaphragm junctions 2. At the molecular level, KIRREL1 recruits SAV1 to cell-cell contact sites, promoting LATS1/2 activation by MST1/2 kinases to suppress YAP/TAZ oncoproteins, establishing a negative feedback loop in Hippo signaling 34. Clinically, KIRREL1 mutations cause steroid-resistant nephrotic syndrome through defective membrane trafficking and impaired podocyte function 2. Circulating anti-KIRREL1 autoantibodies, though rare, represent an emerging biomarker for autoimmune podocytopathies, though detection challenges persist due to transient serum levels and phase-dependent antibody dynamics 5. Beyond nephrology, KIRREL1 acts as a tumor suppressor in YAP/TAZ-active cancers; its expression positively correlates with favorable outcomes, and transgenic expression blocks hepatocellular carcinoma development 4. Recent epigenetic studies identify KIRREL1 dysregulation in colorectal cancer through methylation-sensitive enhancer elements 6. These findings position KIRREL1 as both a critical renal adhesion molecule and potential therapeutic target across glomerular and neoplastic diseases.