FAM149B1 is a DUF3719-domain-containing protein essential for primary cilium assembly and function 1. The protein regulates cilia architecture by promoting CCRK kinase activity to control the localization and function of MAK kinase, thereby modulating axonemal microtubule stability and ciliary length 1. FAM149B1 also participates in intraflagellar transport (IFT) turnaround at the ciliary tip through direct interactions with BROMI/TBC1D32 and CCRK/CDK20, which together regulate ICK/CILK1 kinase-dependent directional switching of the IFT machinery 2. Disruption of FAM149B1 results in ciliary dysfunction characterized by abnormally elongated cilia, accumulation of IFT machinery at the distal ciliary tip, dysregulated sonic hedgehog signaling, and bulbous ciliary morphology 3. Bi-allelic FAM149B1 mutations cause Joubert syndrome 36, a ciliopathy presenting with neurological features including developmental delay, oculomotor apraxia, hypotonia, and skeletal abnormalities 34. Clinical manifestations expand beyond the classic Joubert phenotype to include variable orofaciodigital features, progressive ophthalmoplegia, ataxia, polydactyly, and corpus callosal dysgenesis 4. FAM149B1 was also identified as a biomarker protein in distinguishing follicular thyroid carcinoma from benign follicular adenoma using proteomics analysis 5, though this association requires validation for clinical significance.