Photoreceptor disc incisures form as an adaptive mechanism ensuring the completion of disc enclosure
- Department of Ophthalmology, Duke University Medical Center, United States
- National Center for Microscopy and Imaging Research, School of Medicine, University of California, San Diego, United States
- Eugene Bell Center for Regenerative Biology and Tissue Engineering and National Xenopus Resource, United States
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, United States
Figures
Figure 1
Schematic illustration of incisure arrangements.
(A) Cartoon illustrating the structure of rod photoreceptors in mice and frogs. In each species, the outer segment contains hundreds of disc membranes in a stack. For simplicity, the connecting …
Figure 2
Incisures are observed only in fully enclosed discs of mouse rods.
(A–G) Representative TEM images of longitudinally sectioned WT mouse rods contrasted with a combination of tannic acid and uranyl acetate, which stains newly forming ‘open’ discs more intensely than …
Figure 3 with 1 supplement
Representative z-section from a STEM tomogram of a 750-nm-thick tangential section of a WT mouse retina.
The retina was contrasted with tannic acid/uranyl acetate. Full tomogram is shown in Figure 3—video 1. Because individual rods in the mouse retina are not perfectly aligned, adjacent cells are …
Figure 3—video 1
Tomogram associated with Figure 3.
Field of view: 12.0 µm x 12.0 µm.
Figure 4 with 4 supplements
Disc incisures are observed in mature but not newly forming discs.
(A) Representative z-sections at the depths of 0 (left),+168 (middle) and +244 nm (right) from a reconstructed electron tomogram of a 750 nm-thick WT mouse retinal section. Full tomogram is shown in …
Figure 4—video 1
Tomogram associated with Figure 4A.
Field of view: 1.91 µm x 1.91 µm.
Figure 4—video 2
Tomogram associated with Figure 4B.
Field of view: 1.91 µm x 1.91 µm.
Figure 4—video 3
Tomogram associated with Figure 4C.
Field of view: 1.91 µm x 1.91 µm.
Figure 4—video 4
Tomogram associated with Figure 4D.
Field of view: 1.91 µm x 1.91 µm.
Figure 5 with 1 supplement
Ultrastructure of mature disc incisures.
(A) Representative z-section from a reconstructed electron tomogram of a 750-nm-thick WT mouse retinal section. Full tomogram of the boxed area is shown in Figure 5—video 1. (B) Representative …
Figure 5—video 1
Tomogram associated with Figure 5.
Field of view: 0.63 µm x 0.84 µm.
Figure 6 with 1 supplement
Reduction in peripherin-2 level prevents incisure formation in mouse rods.
(A) Representative TEM images of tangentially sectioned WT outer segments and rds/+ outer segments preserving their cylindrical shape. Yellow asterisks indicate the ciliary axoneme; yellow …
Figure 6—figure supplement 1
Reduction in the level of peripherin-2 but not rhodopsin causes gross abnormalities in outer segment structure.
Representative TEM images of longitudinally sectioned WT, rds/+ and Rho+/- mouse retinas. Scale bar: +/- µm.
Figure 7
Increase in relative peripherin-2 level produces long incisures of varying shape.
(A–C) Representative TEM images of tangentially sectioned Rho+/- mouse retinas. Incisures can be relatively straight and extend nearly the entire disc diameter (A) or be bifurcated or twisted (B). …
Figure 8
Quantification of disc diameters in WT and Rho+/- mouse rods.
Each data point represents a single outer segment. For each genotype, three mice were analyzed (labeled as 1, 2, and 3), with 25 outer segments analyzed in each mouse. Error bars represent mean ± …
Figure 9 with 1 supplement
Loss of peripherin-2 in frogs (Xenopus tropicalis) prevents incisure formation.
(A–D) Representative TEM images of longitudinally sectioned WT and prph2-/- frog retinas. (E,F) Representative TEM images of tangentially sectioned WT and prph2-/- frog retinas. Magenta arrows point …
Figure 9—figure supplement 1
One incisure in frog rod discs is aligned with the ciliary axoneme.
Representative TEM image of a tangentially sectioned WT frog retina. Yellow asterisks indicate the ciliary axoneme; yellow arrowheads point to incisures. Scale bar: 1 µm.
Videos
Video 1
Reconstructed tomogram of a basal body nucleating the ciliary axoneme.
Shown is a 420 nm fragment of a 750-nm-thick retinal section. Tomogram pixel size is 0.7 nm. Field of view: 0.80 µm x 0.80 µm.
Tables
Table 1
Quantification of molar ratios between rhodopsin, peripherin-2 and ROM1 in mouse outer segments.
| Protein molar ratio* | WT | rds/+ | Rho+/- |
|---|---|---|---|
| Rhodopsin: peripherin-2 | 18.2±0.6 | 30.9±6.0 | 8.5±1.5 |
| Rhodopsin: ROM1 | 42.2±0.6 | 29.9±2.0 | 21.6±3.7 |
| Peripherin-2: ROM1 | 2.3±0.1 | 1.0±0.2 | 2.6±0.6 |
| Rhodopsin: (Peripherin-2 +ROM1) | 12.7±0.4 | 15.1±1.8 | 6.0±0.8 |
-
*
Values are shown as mean ± s.d. Three outer segment preparations from mice of each genotype were analyzed.
-
Table 1—source data 1
Quantification of molar ratios between rhodopsin, peripherin-2 and ROM1 in mouse outer segments – raw data.
- https://cdn.elifesciences.org/articles/89160/elife-89160-table1-data1-v2.xlsx
Table 2
Summary of quantitative parameters determined for mouse discs.
| Calculated parameter | WT | Rho+/- |
|---|---|---|
| Disc surface area (both lamellae) | 3.53 µm2 | 1.80 µm2 |
| Rhodopsin molecules per disc | 75,000 | 38,200 |
| Peripherin-2+ROM1 molecules per disc | 5,910 | 6,360 |
| Total rim length | 6.21 µm | N/A* |
| Measured incisure length as % of disc diameter | 50%† | N/A* |
| Theoretical incisure length as % of disc diameter | - | 155% |
-
*
Incisure and total rim lengths in Rho +/- discs cannot be readily measured due to incisure complexity.
-
†
The value is taken from the measurements shown in Figure 6.
Key resources table
| Reagent type (species) or resource | Designation | Source or reference | Identifiers | Additional information |
|---|---|---|---|---|
| strain, strain background (Mus musculus) | C57BL/6 J | Jackson Labs | Jax#:000664 | |
| genetic reagent (Mus musculus) | Rho | Lem et al., 1999 | MGI:2680822 | |
| genetic reagent (Mus musculus) | rds | van Nie et al., 1978 | MGI:1856523 | |
| strain, strain background (Xenopus tropicalis) | Nigerian | National Xenopus Resource | RRID:NXR_1018 | |
| genetic reagent (Xenopus tropicalis) | prph2 | This paper | RRID:NXR_3003 | National Xenopus Resource |
