# Drosophila photoreceptor tethering by a laminin-Eys scaffold

## TL;DR

This study reveals how Drosophila photoreceptors are anchored using a scaffold made of laminin and a proteoglycan called Eys, which helps maintain visual clarity.

## Contribution

The discovery of rhabdomere caps as an extracellular matrix structure that links photoreceptors to cone cells through a laminin-Eys scaffold is novel.

## Key findings

- Rhabdomere caps contain perlecan-rich peaks outlined by a laminin β1 (LanB1) grid.
- Photoreceptors secrete Eys to guide LanB1 and perlecan deposition during development.
- Disruption of LanB1 leads to rhabdomere detachment and impaired tension transmission.

## Abstract

Visual acuity in Drosophila requires precise photoreceptor alignment along the optical axis, maintained by longitudinal tension between a rigid cornea and a contractile retinal base. Here, we identify the rhabdomere caps—an extracellular matrix (ECM) structure that links rhabdomere tips to the integrin-decorated basal surfaces of overlying, lens-forming cone cells. Rhabdomere caps form perlecan-filled peaks shaped by a trapezoidal LanB1 (laminin) grid, which mirrors the inter-rhabdomeral space (IRS) contour. Our study revealed that Eys (eyes shut), a photoreceptor-secreted proteoglycan essential for IRS formation, guides LanB1 and perlecan deposition by cone cells during pupal development. Disruption of LanB1 results in rhabdomere tip detachment, IRS collapse, and impaired tension transmission. These findings reveal that cone cells and photoreceptors collaboratively sculpt a rigid LanB1 grid that caps and reinforces the distal IRS lumen. This composite ECM structure preserves rhabdomere organization and evenly distributes mechanical forces, ensuring photoreceptor alignment and optical fidelity.

•Rhabdomere caps are ECM specializations that tether photoreceptors to cone cells•Rhabdomere caps contain perlecan-rich peaks outlined by a laminin β1 (LanB1) grid•Photoreceptors secrete Eys to pattern the LanB1 grid at the distal IRS•The LanB1 grid shields photoreceptor ends from deformation during morphogenesis

Rhabdomere caps are ECM specializations that tether photoreceptors to cone cells

Rhabdomere caps contain perlecan-rich peaks outlined by a laminin β1 (LanB1) grid

Photoreceptors secrete Eys to pattern the LanB1 grid at the distal IRS

The LanB1 grid shields photoreceptor ends from deformation during morphogenesis

Mechanobiology; Cell biology; Biophysics