CDH9 (cadherin 9) is a calcium-dependent cell adhesion protein that plays critical roles in neural development and disease. As a type II cadherin, CDH9 mediates homophilic cell-cell adhesion and contributes to cell sorting during development 1. In the developing cerebellum, CDH9 exhibits segregated expression patterns in Purkinje cell subpopulations, with complementary expression to CDH11 in autism-relevant regions like lobules VI/VII of the vermis 2. This spatial expression pattern suggests distinct but coordinated functions in regulating autism-relevant neural circuit wiring 2. CDH9 has significant disease associations, particularly with neuropsychiatric disorders. Genome-wide association studies have linked CDH9 with autism spectrum disorders 13, though population-specific variations exist in these associations 3. Additionally, CDH9 variants are associated with lobar intracerebral hemorrhage through amyloid-related mechanisms, with differential expression in brain regions characteristically affected by cerebral amyloid angiopathy 4. In cancer biology, CDH9 functions as a metastasis suppressor, where its inhibition enhances cell migration in breast cancer models 5. The gene also shows altered expression in blastocysts from infertile patients and responds to microRNA regulation 67, indicating broader roles in development and cellular regulation.