Deletion of the presynaptic scaffold CAST reduces active zone size in rod photoreceptors and impairs visual processing.

How size and shape of presynaptic active zones are regulated at the molecular level has remained elusive. Here we provide insight from studying rod photoreceptor ribbon-type active zones after disruption of CAST/ERC2, one of the cytomatrix of the active zone (CAZ) proteins. Rod photoreceptors were present in normal numbers, and the a-wave of the electroretinogram (ERG)--reflecting their physiological population response--was unchanged in CAST knock-out (CAST(-/-)) mice.

Stability of active zone components at the photoreceptor ribbon complex.

Purpose: Photoreceptor ribbon synapses translate light-dependent changes of membrane potential into graded transmitter release over several orders of magnitude in intensity. A specialized organelle at the active zone--the synaptic ribbon--is a key player in this process, and it is well known that the ribbon undergoes illumination and thus activity-dependent structural changes. However, the molecular basis for these changes is unknown.

Early steps in the assembly of photoreceptor ribbon synapses in the mouse retina: the involvement of precursor spheres.

The retinal photoreceptor ribbon synapse is a chemical synapse structurally and functionally specialized for the tonic release of neurotransmitter. It is characterized by the presynaptic ribbon, an electron-dense organelle at the active zone covered by hundreds of synaptic vesicles. In conventional synapses, dense-core transport vesicles carrying a set of active zone proteins are implicated in early steps of synapse formation.

Effects of presynaptic mutations on a postsynaptic Cacna1s calcium channel colocalized with mGluR6 at mouse photoreceptor ribbon synapses.

Purpose: Photoreceptor ribbon synapses translate light-dependent changes of membrane potential into graded transmitter release via L-type voltage-dependent calcium channel (VDCC) activity. Functional abnormalities (e.g.

Type 4 OFF cone bipolar cells of the mouse retina express calsenilin and contact cones as well as rods.

Immunocytochemical discrimination of distinct bipolar cell types in the mouse retina is a prerequisite for analyzing retinal circuitry in wild-type and transgenic mice. Here we demonstrate that among the more than 10 anatomically defined mouse bipolar cell types, type 4 bipolar cells are specifically recognized by anti-calsenilin antibodies. Axon terminals in the inner plexiform layer are not readily identifiable because calsenilin is also expressed in a subset of amacrine and ganglion cells.

Structural and functional remodeling in the retina of a mouse with a photoreceptor synaptopathy: plasticity in the rod and degeneration in the cone system.

Knowledge about the plastic and regenerative capacity of the retina is of key importance for therapeutic approaches to restore vision in patients who suffer from degenerative retinal diseases. In the retinae of mice, mutant for the presynaptic scaffolding protein Bassoon, signal transfer at photoreceptor ribbon synapses is disturbed due to impaired ribbon attachment to the active zone. In a long-term study we observed, with light and electron microscopic immunocytochemistry and electroretinographic recordings, two overlapping events in the Bassoon mutant retina, i.