Abstract
Cilia are microtubule-based hair-like organelles that extend from the cell surface. However, the existence and distribution of cilia in each organ and tissue at the postnatal stage in vivo remain largely unknown. In this study, we defined cilia distribution and arrangement and measured the ciliary lengths and the percentage of ciliated cells in different organs and tissues in vivo by using cilium dual reporter-expressing transgenic mice. Cilia were identified by the presence of ARL13B with an mCherry+ signal, and the cilium basal body was identified by the presence of Centrin2 with a GFP+ signal. Here, we provide in vivo evidence that chondrocytes and cells throughout bones have cilia. Most importantly, we reveal that: 1. primary cilia are present in hepatocytes; 2. no cilia but many centrioles are distributed on the apical cell surface in the gallbladder, intestine, and thyroid epithelia; 3. cilia on the cerebral cortex are well oriented, pointing to the center of the brain; 4. ARL13B+ inclusion is evident in the thyroid and islets of Langerhans; and 5. approximately 2% of cilia show irregular movement in nucleus pulposus extracellular fluid. This study reveals the existence and distribution of cilia and centrioles in different tissues and organs, and provides new insights for further comprehensive study of ciliary function in these organs and tissues.
Highlights
Cilia are microtubule-based organelles that were first discovered by Leeuwenhoek in approximately 1675
Using the described genetic mouse model, we first confirmed that mCherry marks cilia in mouse tissues (Figures S1 and S2) via immunofluorescence staining of ARL13B and acetylated tubulin in tracheal tissue
MCherry+ primary cilia were detected in 72.2 ± 1% of chondrocytes, and the length of primary cilia varied between 3 and 5 μm, consistent with the number and length of primary cilia in chondrocytes of articular cartilage [11] (Figure 1A) (Table 1)
Summary
Cilia are microtubule-based organelles that were first discovered by Leeuwenhoek in approximately 1675. To further identify cells with cilia, we tested for the presence of cilia and characterized the distribution of cilia in different organs and tissues by using a unique cilium double-reporter transgenic mouse model [1]. In this model, the ciliary protein ARL13B is fused with the monomeric red fluorescent protein mCherry, and the centriolar protein Centrin is fused with GFP to mark the cilium basal body. The ARL13B-mCherry;Centrin2-GFP cilium dual-reporter transgenic mouse line has been proven to exhibit successful labeling of cilia with mCherry and labeling of basal bodies with GFP, and the mice are viable and fertile without disruption of normal ciliary function [1]
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