TCTN1 (tectonic family member 1) is a ciliary transition zone protein with dual roles in developmental signaling and cancer progression. Structurally, TCTN1 functions as a component of the tectonic-like complex localized at the ciliary transition zone, where it acts as a barrier regulating transmembrane protein diffusion 1. TCTN1 regulates Hedgehog signaling, required for both pathway activation during neural tube patterning and repression in the absence of Hh signals, functioning downstream of SMO and RAB23. Beyond its developmental role, TCTN1 demonstrates oncogenic properties across multiple cancer types. In melanoma, TCTN1 promotes metastasis by acting as a protein scaffold facilitating binding of mitochondrial trifunctional protein subunits HADHA and HADHB, activating fatty acid oxidation and p38/MAPK signaling 2. High TCTN1 expression correlates with increased metastasis and shorter survival. In glioblastoma, elevated TCTN1 expression predicts poor prognosis and promotes cell proliferation through molecular subtype-dependent mechanisms 3. TCTN1 knockdown inhibits proliferation and induces apoptosis in thyroid cancer 4, colorectal cancer 5, and oral squamous cell carcinoma 6. Clinically, TCTN1 mutations cause Joubert syndrome type 13, characterized by cerebellar malformations and developmental delay 7. Unlike other ciliopathies, TCTN1-associated disease shows minimal ocular involvement 8.