Fig. 5.

OS detachment from the photoreceptor cell body is increased in pcdh15b mutants. (A) Representative TEM images of OS detachment and floating OSs seen in pcdh15b mutants (Δ7 and ins17), compared to wild-type siblings. Magenta is used for IS with no OS; green is used for detached ‘floating’ OS. These phenomena are rarely observed in wild-type siblings. (B) Close-up TEM examples of IS-OS connection in photoreceptors of wild-type siblings and Δ7 and ins17 mutants, showing the process of detachment. CPs are visible as protrusions coming up from the IS (green) and attaching to the sides of the OS (arrows point to the sides). pcdh15b mutants (Δ7/Δ7 and ins17/ins17) show a range of affected connections (i-v), coincident with the loss of CP (magenta-coloured boxes) attachments on the sides (arrows). (C) Schematic of the OS detachment seen in pcdh15b mutants. The relevant Pcdh15 expression found at the OS base is highlighted in magenta. The green box highlights the IS-OS connection. (D) Quantification of the percentage of total identified photoreceptor IS/cell bodies with attached or completely detached/missing OSs across the entire ONL from 5 dpf to 15 dpf. Statistical analyses were performed using Student's t-test (unpaired, two-tailed). ***P≤0.001, ****P≤0.0001. Number of eyes/PRs analysed: 5 dpf: +/+, 10 eyes/1780 PRs; Δ7/Δ7, 10 eyes/1473 PRs; 10 dpf: +/+, 9 eyes/1844 PRs; Δ7/Δ7, 12 eyes/2290 PRs; 15 dpf: +/+, 6 eyes/334 PRs; Δ7/Δ7, 6 eyes/474 PRs; 10 dpf: +/+, 8 eyes/1253 PRs; ins17/ins17, 7 eyes/1087 PRs. CP, calyceal process; IS, inner segment; ONL, outer nuclear layer; OS, outer segment; PR, photoreceptor.