Human photoreceptor outer segments shorten during light adaptation

Quantitative fundus autofluorescence and optical coherence tomography in best vitelliform macular dystrophy

PURPOSE

Quantitative fundus autofluorescence (qAF), spectral domain optical coherence tomography (SD-OCT) segmentation, and multimodal imaging were performed to elucidate the pathogenesis of Best vitelliform macular dystrophy (BVMD) and to identify abnormalities in lesion versus nonlesion fundus areas.

METHODS

Sixteen patients with a clinical diagnosis of BVMD were studied. Autofluorescence images (30°, 488-nm excitation) were acquired with a confocal scanning laser ophthalmoscope equipped with an internal fluorescent reference to account for variable laser power and detector sensitivity. The grey levels (GLs) of each image were calibrated to the reference, zero GL, magnification, and normative optical media density, to yield qAF. Horizontal SD-OCT scans were obtained and retinal layers manually segmented. Additionally, color and near-infrared reflectance (NIR-R) images were registered to AF images. All patients were screened for mutations in BEST1. In three additional BVMD patients, in vivo spectrofluorometric measurements were obtained within the vitelliform lesion.

RESULTS

Mean nonlesion qAF was within normal limits for age. Maximum qAF within the lesion was markedly increased compared with controls. By SD-OCT segmentation, outer segment equivalent thickness was increased and outer nuclear layer thickness decreased in the lesion. Changes were also present in a transition zone beyond the lesion border. In subclinical patients, no abnormalities in retinal layer thickness were identified. Fluorescence spectra recorded from the vitelliform lesion were consistent with those of retinal pigment epithelial cell lipofuscin.

CONCLUSIONS

Based on qAF, mutations in BEST1 do not cause increased lipofuscin levels in nonlesion fundus areas.

Primary cilia and dendritic spines: different but similar signaling compartments

Primary non-motile cilia and dendritic spines are cellular compartments that are specialized to sense and transduce environmental cues and presynaptic signals, respectively. Despite their unique cellular roles, both compartments exhibit remarkable parallels in the general principles, as well as molecular mechanisms, by which their protein composition, membrane domain architecture, cellular interactions, and structural and functional plasticity are regulated. We compare and contrast the pathways required for the generation and function of cilia and dendritic spines, and suggest that insights from the study of one may inform investigations into the other of these critically important signaling structures.