Figure 8.
Figure 8. Amphid cilia are shortened and have abnormal microtubule structure in nphp-4 mutants. TEM of amphid channel cilia in the wild type (a–c, h, and j) and nphp-4 (d–f, i, and k–m). In nphp-4, some distal segments are shortened; panel d shows 6 out of the normal 10 distal segments that should be present. Middle segments (e, i, and m) are sometimes swollen or withered. Because of slight cilia bending, views of individual microtubules within a cilium are sometimes seen obliquely and seem distorted; when tilted in the microscope, those distortions go away. Occasionally the channel contains <10 cilia; in panel e, nine are present, suggesting that at least one cilium is completely absent past the TZ. Some middle segments have microtubule doublets abnormally converting prematurely to singlets lacking B tubules (e and i, arrowhead) or abnormal doublets with an inner seam break of the B tubule (i, arrows), whereas others appear normal. Such inner seam breaks are also found in wild-type cilia of ADL and ASI (h, arrows) but become much more common in other cilia in nphp-4 (i, k, and l). Schematic cartoon (g) displays the region of the middle segment where seam breaks are common in ADL (wild type and mutant) and in ASJ mutant cilia, seen from a lateral aspect. In wild-type and nphp-4 ADL cilia, all microtubules tend to have long continuous seam breaks. In ASJ, shorter, discontinuous seam breaks are scattered along the middle segment, but only in nphp-4 animals. Small spurs can also be seen on the outer surface of many A tubules within the middle segment, looking vaguely similar to Y-link features of the axoneme (compare c with k–m). Panel m shows a nphp-4 ADL cilium, just distal to the axoneme, where an increased number of microtubule doublets surround the outer edge (13 rather than 8–9), most showing B tubule seam breaks; some inner “singlets” even have partial B tubules. This represents a fused cilium (seen in 2/6 amphids in nphp-4); ADL normally forms two separate cilia (g). (i) An electron-dense mass that may represent jammed IFT particles. TZs are typically well-formed in nphp-4 mutants (f). Bars: (a) 0.5 μm; (h) 0.5 μm; (j) 100 nm.

Amphid cilia are shortened and have abnormal microtubule structure in nphp-4 mutants. TEM of amphid channel cilia in the wild type (a–c, h, and j) and nphp-4 (d–f, i, and k–m). In nphp-4, some distal segments are shortened; panel d shows 6 out of the normal 10 distal segments that should be present. Middle segments (e, i, and m) are sometimes swollen or withered. Because of slight cilia bending, views of individual microtubules within a cilium are sometimes seen obliquely and seem distorted; when tilted in the microscope, those distortions go away. Occasionally the channel contains <10 cilia; in panel e, nine are present, suggesting that at least one cilium is completely absent past the TZ. Some middle segments have microtubule doublets abnormally converting prematurely to singlets lacking B tubules (e and i, arrowhead) or abnormal doublets with an inner seam break of the B tubule (i, arrows), whereas others appear normal. Such inner seam breaks are also found in wild-type cilia of ADL and ASI (h, arrows) but become much more common in other cilia in nphp-4 (i, k, and l). Schematic cartoon (g) displays the region of the middle segment where seam breaks are common in ADL (wild type and mutant) and in ASJ mutant cilia, seen from a lateral aspect. In wild-type and nphp-4 ADL cilia, all microtubules tend to have long continuous seam breaks. In ASJ, shorter, discontinuous seam breaks are scattered along the middle segment, but only in nphp-4 animals. Small spurs can also be seen on the outer surface of many A tubules within the middle segment, looking vaguely similar to Y-link features of the axoneme (compare c with k–m). Panel m shows a nphp-4 ADL cilium, just distal to the axoneme, where an increased number of microtubule doublets surround the outer edge (13 rather than 8–9), most showing B tubule seam breaks; some inner “singlets” even have partial B tubules. This represents a fused cilium (seen in 2/6 amphids in nphp-4); ADL normally forms two separate cilia (g). (i) An electron-dense mass that may represent jammed IFT particles. TZs are typically well-formed in nphp-4 mutants (f). Bars: (a) 0.5 μm; (h) 0.5 μm; (j) 100 nm.

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