RASGEF1A encodes a guanine nucleotide exchange factor (GEF) with specific activity toward RAP2 proteins and broader activity toward KRAS, HRAS, and NRAS in vitro 12. The protein contains a C-terminal CDC25-Ras exchange motif domain and an N-terminal RasGEF-N domain that confer Rap2-specific nucleotide exchange activity 1. RASGEF1A functions in cell migration and Ras protein signal transduction 2, with elevated expression driving enhanced cellular motility and proliferation in cholangiocarcinoma cells 2. Clinically, RASGEF1A dysregulation associates with multiple disease contexts. Enhanced RASGEF1A expression promotes intrahepatic cholangiocarcinoma growth and progression, suggesting therapeutic potential for targeted suppression 2. Genome-wide association studies identify the RET-CSGALNACT2-RASGEF1A genomic region as a significant susceptibility locus for Hirschsprung disease, with differential effects across disease subgroups 34. RASGEF1A participates in chr10 rearrangements: novel RASGEF1A-RET and non-immunoglobulin/BCL6 fusions occur in breast cancer and diffuse large B-cell lymphoma respectively, with the latter associated with poor prognosis 56. Constitutional translocations disrupting RASGEF1A link to renal cell carcinoma predisposition 7. These findings establish RASGEF1A as a multifunctional GEF relevant to developmental and malignant disease pathways.