Figure 7.
Deficiency of Kif6, but not Kif9, impairs the rotational polarity of BBs in ependymal tissues. Quantification results were pooled together (mean ± SD plus sample dots) and subjected to unpaired two-tailed student’s t test. Se, Severe hydrocephalus. Mi, Mild hydrocephalus. (A) Schematic diagrams of a motile cilium and an array of rotationally polarized BBs. (B)Kif6 deficiency did not alter the overall axonemal ultrastructure. Shown are typical transverse views of ependymal cilia, representing transmission electron microscopic results from two wild-type and two Kif6−/− mice. (C and D) BB polarities assessed using transmission electron microscopy. Arrows indicate BB polarities in the representative electron micrographs (C), based on the BF orientation. At least ten full-size electron micrographs, each containing at least 6 BBs with clear BFs, were used for quantification. The extent of the rotational polarity in each micrograph was calculated as the mean vector length of all the BBs by considering each arrow marking their polarities as a unit vector (D). (E and F) BB polarities assessed using 3D-SIM. Ependymal tissues from the indicated mice were immunostained for Cep164 to visualize BBs and γ-tubulin to visualize BFs. Framed regions in E were magnified to show detailed BB polarities (arrows). The extent of the rotational polarity for a BB patch (BBs in a cell) was calculated as the mean vector length of all the BBs with clear BFs by considering each arrow marking their polarities as a unit vector. Quantification results (F) were from two P34 and one P43 Kif6−/− mice with severe (Se) hydrocephalus, one P62 Kif6−/− mouse with mild (Mi) hydrocephalus, and three of their wild-type littermates; and two 6-month-old (6 M) and one 7-month-old Kif9−/− mice and three wild-type littermates. 20 multiciliated ependymal cells were scored for each mouse. (G) Representative 3D-SIM images of ependymal tissues from the indicated mice. BB patches magnified from the framed regions are presented in E. Arrows indicate directions of the rotational polarity of BB patches, based on the major polarities of the BBs. Note that the arrows in each micrograph point to similar directions. No arrows are drawn for the Kif6−/− BB patches due to their lack of the rotational polarity (F). (H) A summarization model. Kif6 may act as an accessory motor to assist anterograde IFT or be transported by the IFT machinery as a cargo for speedy delivery. It may also function as an independent motor on DMTs to transport cargos into motile cilia to facilitate the establishment of rotational polarity. On the other hand, Kif9 localizes on the C2 MT to fine-tune ciliary or flagellar beat by inducing conformational changes in the central apparatus, similar to its Chlamydomonas counterpart KLP1 (Han et al., 2022). TZ, transition zone.

Deficiency of Kif6, but not Kif9, impairs the rotational polarity of BBs in ependymal tissues. Quantification results were pooled together (mean ± SD plus sample dots) and subjected to unpaired two-tailed student’s t test. Se, Severe hydrocephalus. Mi, Mild hydrocephalus. (A) Schematic diagrams of a motile cilium and an array of rotationally polarized BBs. (B)Kif6 deficiency did not alter the overall axonemal ultrastructure. Shown are typical transverse views of ependymal cilia, representing transmission electron microscopic results from two wild-type and two Kif6−/− mice. (C and D) BB polarities assessed using transmission electron microscopy. Arrows indicate BB polarities in the representative electron micrographs (C), based on the BF orientation. At least ten full-size electron micrographs, each containing at least 6 BBs with clear BFs, were used for quantification. The extent of the rotational polarity in each micrograph was calculated as the mean vector length of all the BBs by considering each arrow marking their polarities as a unit vector (D). (E and F) BB polarities assessed using 3D-SIM. Ependymal tissues from the indicated mice were immunostained for Cep164 to visualize BBs and γ-tubulin to visualize BFs. Framed regions in E were magnified to show detailed BB polarities (arrows). The extent of the rotational polarity for a BB patch (BBs in a cell) was calculated as the mean vector length of all the BBs with clear BFs by considering each arrow marking their polarities as a unit vector. Quantification results (F) were from two P34 and one P43 Kif6−/− mice with severe (Se) hydrocephalus, one P62 Kif6−/− mouse with mild (Mi) hydrocephalus, and three of their wild-type littermates; and two 6-month-old (6 M) and one 7-month-old Kif9−/− mice and three wild-type littermates. 20 multiciliated ependymal cells were scored for each mouse. (G) Representative 3D-SIM images of ependymal tissues from the indicated mice. BB patches magnified from the framed regions are presented in E. Arrows indicate directions of the rotational polarity of BB patches, based on the major polarities of the BBs. Note that the arrows in each micrograph point to similar directions. No arrows are drawn for the Kif6−/− BB patches due to their lack of the rotational polarity (F). (H) A summarization model. Kif6 may act as an accessory motor to assist anterograde IFT or be transported by the IFT machinery as a cargo for speedy delivery. It may also function as an independent motor on DMTs to transport cargos into motile cilia to facilitate the establishment of rotational polarity. On the other hand, Kif9 localizes on the C2 MT to fine-tune ciliary or flagellar beat by inducing conformational changes in the central apparatus, similar to its Chlamydomonas counterpart KLP1 (Han et al., 2022). TZ, transition zone.

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