TTC23 is a tetratricopeptide repeat domain protein that functions in ciliary Hedgehog signaling and cilium biology. TTC23 positively regulates smoothened signaling pathway and participates in protein binding within ciliary structures 1. As a ciliary protein, TTC23 variants are implicated in ciliopathies, a heterogeneous class of disorders affecting primary cilium function; functional assays on patient-derived fibroblasts support TTC23's role in ciliary pathology 1. Beyond ciliary function, TTC23 has been identified in cancer genomics contexts, including as part of a novel IGF1R/TTC23 fusion transcript in bladder cancer 2 and in alternative splicing changes during hypoxic stress in prostate cancer cells 3. Recent evidence indicates TTC23 functions downstream of BATF2 transcription factor in macrophages infected with Mycobacterium tuberculosis, where it regulates immune cell proliferation and antibacterial capacity through the Wnt/β-catenin pathway; elevated TTC23 expression correlates with pulmonary tuberculosis 4. Additionally, TTC23 methylation patterns associate with opioid medication use 5 and tinnitus 6, suggesting epigenetic regulation. The protein represents a multifunctional molecule with primary significance in ciliary Hedgehog signaling while showing emerging importance in immune response and disease-associated epigenetic modifications.