Figure 3

Representative Electron Micrographs of AIPL1-LCA ROs. (A) Ultrastructure of the ONL-like region: ISs protruding at the apical side of the organoid, cone-like cells (C) at the outermost side of the ONL with large cell body and large bright nucleus and cytoplasmic mitochondria (white arrow). Deeper aligned, presumably rod photoreceptors with electron dark nuclei (r). White square showing the area where synaptic ribbons identified. (A’) Higher magnification of ISs (black arrowheads) at the apical border with elongated mitochondria (white arrowheads) and OLM (white arrows). (B) Longitudinal section of CC (white arrow) arising from the ISs with the BB at the base and the Ce at a right angle below the BB. The transversal section of the CC reflecting microtubules arranged to form a cylinder (black arrow). (C) CC protrudes into organelle-free vesicle with membranous structure precursors of the disc stacks (white arrowhead) of the OSs. (D) CC arising from the IS and a transversal section of the CC lying in the area outward of the IS (white arrows). Dark cross-striation representing rootlet filaments (black arrowheads, Ro) protruding from the BB toward the cytoplasm. Organelle free vesicles, presumably presenting nascent OSs (black arrows), observed in the vicinity of the CC outward of ISs. (E,E’). Multiple synaptic ribbons with electron dense bars (white arrowheads) surrounded by presynaptic vesicles (white arrows). Abbreviations: ONL, outer nuclear layer; ISs, inner segments; OLM, outer limiting membrane; CC, connecting cilium; BB, basal body; Ce, centriole; Ro, rootlets; OS, outer segment.