CSPP1 (centrosome and spindle pole associated protein 1) is a microtubule-stabilizing protein with primary roles in ciliary and centrosomal function. Mechanistically, CSPP1 stabilizes microtubules by binding to polymerizing microtubule ends and depositing within the microtubule lumen, where it inhibits both growth and shortening through distinct molecular domains 1. CSPP1 additionally caps and stabilizes both plus and minus ends of static microtubules by suppressing catastrophe and restricting polymerization 2. The protein specifically recognizes and stabilizes damaged microtubule lattices 1, supporting the elongation and stability of ciliary axonemes and other microtubule-based structures. Disease relevance centers on Joubert syndrome 21, a neurodevelopmental ciliopathy characterized by hindbrain malformation and multi-systemic involvement including ocular and renal pathologies 3. CSPP1 functions within a ciliary protein module with ARMC9 and TOGARAM1; dysfunction of this module causes short cilia with decreased axonemal modifications and aberrant ciliary stability 4. Clinic significance extends beyond ciliopathies: circular RNA derived from CSPP1 (circ-CSPP1) regulates cancer progression in hepatocellular carcinoma, non-small cell lung cancer, and glioma through competing endogenous RNA mechanisms 567. Nuclear CSPP1 isoforms identify distinct breast cancer subtypes with prognostic implications 8.