# Special nuclear layer contacts between starburst amacrine cells in the mouse retina

## TL;DR

This study reveals that starburst amacrine cells in the mouse retina have unexpected contacts in the nuclear layer, challenging previous assumptions about their structure and function.

## Contribution

The study provides the first anatomical evidence of special nuclear layer contacts between starburst amacrine cells in the mouse retina.

## Key findings

- Starburst amacrine cells have dendrites reaching into the nuclear layer, contrary to their typical stratification in the inner plexiform layer.
- Both On and Off subpopulations of starburst amacrine cells form somatic contacts in the nuclear layer.
- Electron microscopic reconstructions revealed distinct contact patterns between the two subpopulations.

## Abstract

Starburst amacrine cells are a prominent neuron type in the mammalian retina that has been well-studied for its role in direction-selective information processing. One specific property of these cells is that their dendrites tightly stratify at specific depths within the inner plexiform layer (IPL), which, together with their unique expression of choline acetyltransferase (ChAT), has made them the most common depth marker for studying other retinal neurons in the IPL. This stratifying property makes it unexpected that they could routinely have dendrites reaching into the nuclear layer or that they could have somatic contact specializations, which is exactly what we have found in this study. Specifically, an electron microscopic image volume of sufficient size from a mouse retina provided us with the opportunity to anatomically observe both microscopic details and collective patterns, and our detailed cell reconstructions revealed interesting cell-cell contacts between starburst amacrine neurons. The contact characteristics differ between the respective On and Off starburst amacrine subpopulations, but both occur within the soma layers, as opposed to their regular contact laminae within the inner plexiform layer.