KCTD1 (potassium channel tetramerization domain containing 1) is a nuclear transcriptional repressor that plays critical roles in developmental signaling and cellular regulation 1. The protein contains an N-terminal BTB (broad-complex, tramtrack, and bric-a-brac) domain that mediates both transcriptional repression and homomeric protein-protein interactions 1. KCTD1 functions as a general regulator of multiple developmental pathways, strongly inhibiting Wnt, Hedgehog, and Notch signaling cascades 2. Additionally, it modulates G protein-coupled receptor signaling by increasing adenylyl cyclase type 5 (AC5) abundance, thereby enhancing neuronal cAMP signaling in response to dopamine 23. KCTD1 forms multimeric complexes with KCTD15 and can compensate for each other's loss 4. Disease-causing mutations in KCTD1 are associated with scalp-ear-nipple syndrome, causing aplasia cutis congenita, ectodermal abnormalities, and kidney fibrosis 4. The protein exhibits oncosuppressive properties in colorectal cancer, with its downregulation associated with increased cell motility, stemness, and β-catenin overexpression 5. KCTD1's structural analysis reveals an unexpected pentameric assembly with ion-binding properties that contribute to its transcription factor binding capabilities 6.