Ift20, initially discovered as the smallest component of the intraflagellar transport (IFT) system, is crucial for the assembly and maintenance of the primary cilium. It is also involved in vesicular trafficking of membrane receptors and signaling proteins, and regulates intracellular degradative and secretory pathways [1]. Genetic models, such as KO/CKO mouse models, have been instrumental in studying its functions.

In KO mouse models, Ift20 deficiency in early-stage mesenchymal stem cells (MSCs) led to shortened limbs, decreased bone mass, and increased marrow fat, indicating its role in regulating MSC lineage allocation through glucose metabolism [2]. Deletion of Ift20 in craniofacial osteoblasts caused bone defects and altered collagen cross-linking, showing its importance in collagen biosynthesis [3]. In breast cancer cells, Ift20 knockdown enhanced apoptosis in response to paclitaxel, suggesting its role in conferring paclitaxel resistance [4]. In condylar cartilage, deletion of Ift20 reduced cell proliferation, decreased Golgi size, and attenuated Hedgehog signaling, highlighting its requirement for maintaining cartilaginous matrix [5]. Exclusive deletion of Ift20 in the retinal pigment epithelium (RPE) ablated primary cilia, led to retinal degeneration, and impaired vision [6]. In kidney epithelial cells, Dlg1 regulates ciliary protein trafficking, with loss of Dlg1 reducing Ift20 and other proteins in cilia [7]. In breast cancer cells lacking primary cilia, knockout of Ift20 promoted epithelial-mesenchymal transitions and cell migration [8]. Genetic ablation of Ift20 in epidermal cells slowed keratinocyte migration during wound healing, affecting integrin recycling and focal adhesion dynamics [9]. In Caenorhabditis elegans, the Ift20 homolog is important for cilium assembly and cilia-mediated behavior [10].

In conclusion, Ift20 is essential for ciliogenesis, cell fate determination, metabolism, collagen biosynthesis, and cell migration. KO/CKO mouse models have revealed its significance in diseases such as bone marrow osteoblast-adipocyte imbalance, craniofacial bone defects, breast cancer chemoresistance, and retinal degeneration. These studies provide valuable insights into the biological functions of Ift20 and potential therapeutic targets for related diseases.