The rod synapse in aging wildtype and Dscaml1 mutant mice

Area of Science:

• Neuroscience
• Ophthalmology
• Genetics

Background:

• The retina's rod and cone pathways are essential for vision.
• Genetic mutations affecting the rod circuit cause blinding diseases like retinitis pigmentosa and congenital stationary night blindness (CSNB).
• Down Syndrome cell adhesion molecule like 1 (Dscaml1) is implicated in CSNB, but its precise role is unknown.

Purpose of the Study:

• To investigate the role of Dscaml1 in the maintenance of the rod-to-rod bipolar cell (RBC) synapse.
• To understand how Dscaml1 dysfunction contributes to visual deficits.

Main Methods:

• Utilized a Dscaml1 loss-of-function mouse model.
• Employed immunohistochemistry to study synapse formation and maintenance in retinas of varying ages.
• Generated 3D reconstructions from serial electron micrographs to analyze synaptic structures and mitochondrial morphology.

Main Results:

• Dscaml1 mutant retinas showed increased invaginating neurites in rod spherules and reduced RBC dendritic tips.
• Mitochondrial volume and complexity were decreased in Dscaml1 mutant RBCs.
• Precocious sprouting of RBC dendrites into the outer nuclear layer was observed in mutants.

Conclusions:

• Dscaml1 plays a significant role in the development and maintenance of the rod circuit.
• Synaptic and mitochondrial abnormalities in Dscaml1 mutants offer insights into CSNB pathogenesis.
• Findings suggest potential genetic therapy targets for blinding disorders like CSNB.