CHR3 (chordin) is a secreted dorsalizing protein essential for early vertebrate embryonic development. It functions as a negative regulator of bone morphogenetic protein (BMP) signaling by binding to ventralizing TGF-β family BMPs and sequestering them in latent, inactive complexes, thereby controlling dorsal-ventral axis patterning during gastrulation 1. While murine chordin expression is highest in 7-day postcoitum embryos and decreases substantially at later developmental stages, the gene remains expressed in adult tissues including liver and cerebellum, suggesting roles beyond early development 1. Clinical relevance of CHR3 extends beyond its developmental function. Mutations are associated with skeletal abnormalities including auriculocondylar syndrome 4, branchiogenic deafness syndrome, and cleft lip/palate. More recently, a 2023 study identified that CHR3 is amplified in the DNA of specific cancers such as lung squamous cell carcinoma, and in renal and stomach carcinomas, elevated CHR3 expression significantly correlated with poor survival 2. Additionally, CHR3 has emerged as a component of the BMP signaling pathway in reproductive biology; increased BMP1 binding to CHR3 releases sequestered BMP4, activating BMP/Smad signaling during endometrial decidualization, with reduced CHR3-BMP1 interactions observed in miscarriage cases 3. These findings establish CHR3 as both a developmental regulator and a gene with disease implications in cancer and pregnancy complications.