Retinal cone photoreceptor arrangements were studied in 11 species of Malagasy lemurs. The diversity of cone patterns ranges from relatively high cone densities and the presence of medium-to-longwave-sensitive (green) as well as shortwave-sensitive cones (magenta) in the diurnal sifaka (top) to low cone densities and an absence of shortwave-sensitive cones in the nocturnal dwarf lemurs (bottom).

Using immunocytochemistry and electron microscopy at various gestational time points in human and monkey retinas, this study suggests an intrinsically programmed, nonsynchronous expression of molecules in cone synaptic development. Ribbon synapses at foveal cone pedicles are present at midgestation in monkeys, and perhaps also in humans.

We examined the postnatal development, dendritic protein distribution and synaptogenesis of mouse rod bipolar cells by using 3D reconstructions of both conventional and high-resolution confocal images. We demonstrate that rod bipolar cells: (a) target the appropriate number of rods during development, (b) independently traffic mGluR6 and TRPM1 to dendrites, and (c) may connect to a larger number of rods than previously reported.

This study explores the roles of the extracellular matrix in the organization of the photoreceptor synapse. In wild-type (WT) retina, proteins associated with the release mechanism in the photoreceptor terminal (kinesin and bassoon) are apposed to components of the post-synaptic signaling cascade (mGluR6, GPR179) in the bipolar dendrite. The extracellular complex (including laminins and pikachurin) interacts with putative receptors (integrins, α- and β- dystroglycan). In the absence of laminin β2 (KO), this trans-synaptic organization is disrupted and the scaffolding of the post-synaptic cascade is disorganized, resulting in decreased signaling between photoreceptors and depolarizing bipolar cells.

Ultrastructural and network graph visualization allows mapping of amacrine cell motifs whereby cone bipolar cells inhibit rod bipolar cells (C motifs) and vice versa (R motifs). Many crossover synapses are exceptionally large, which may be a signature for synaptic winner-take-all switches.

This study examined synaptic connections between retinal ganglion cells and the AII amacrine cell, which is a component of the night vision circuit in mammalian retina (rods → rod bipolar cells → AII amacrine cell). Using a physiological assay, combined with morphological analysis, we show that a direct inhibitory synapse from AII amacrine cells is limited to a privileged minority of ganglion cell types. More generally, co-stratification did not reliably predict synaptic connection in the inner plexiform layer.

VIP-Confetti fluorescent amacrine cell types in the VIP-Confetti (Brainbow2.1) retina and their stratification. (a, c, d) VIP-1 cells. (b, e, f) VIP-2 cells. VIP cells are in magenta and calretinin-immunoreactive cells are in green. Scale bar: 25 μm.

In this study we show that the structural and functional integrity of retinal amacrine cells are compromised in a mouse model of glaucoma. Specific immunocytochemical markers were used to identify amacrine cell subpopulations in both the inner nuclear and ganglion cell layers. Calretinin- and GABA- immunoreactive cells were highly vulnerable to glaucomatous damage, whereas ChAT-positive and glycinergic amacrine cell subtypes were largely unaffected. This difference between amacrine cell subtypes appears to be related to their gap junctional coupling patterns. Amacrine cells that are coupled to ganglion cells were lost in glaucoma, whereas uncoupled amacrine cells were not. Our results suggest that amacrine cell loss in glaucoma occurs secondary to ganglion cell death through the gap junction–mediated bystander effect.

Human cholinergic (ChAT) amacrine cells are first observed in the fovea at early-gestation around fetal week (Fwk) 10, and become evident across the retina with age. Characteristic ON and OFF populations of ChAT cells with processes stratifying in separate bands in the synaptic neuropil emerge in the fovea by Fwk 11, and are present as late as mid-gestation (Fwk 20). Previous work, however, demonstrate very few, if any, OFF ChAT-immunoreactive cells in the adult human fovea (Rodieck & Marshak, ). Thus, mechanisms must act to regulate ChAT expression differentially in the ON and OFF populations as the retina matures beyond mid-gestation.