#eye development

Gleeful Look

Glial cells are like an unsung network of city support workers – regulating traffic, sweeping streets, keeping things orderly and hygienic in our brain and nervous system. Their shape is key to how they interact with brain cells, but current techniques to assess this morphology are limited. A new imaging tool, GliaMorph, combines different modules to in turn quantify texture, segmentation, and other features at the individual cell and global scale. Researchers turned GliaMorph’s focus to zebrafish Müller glia – cells important to eye health. They were able to measure Müller glia development, observing the growing complexity and rearrangement (pictured, at 72 - top - and 120 - bottom - hours post fertilisation) – with the original image on the left followed left to right by segmentation, structural edges, distance between elements, and the cellular skeleton highlighted. They then measured changing protein positioning in a mouse model of glaucoma, showing the approach’s direct potential for revealing the precise morphology of human disease.

Written by Anthony Lewis

Image from work by Elisabeth Kugler and colleagues

Institute of Ophthalmology, University College London, London, UK

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Development, February 2023

Beautiful Eyes

If you look at a clear blue sky it’s possible to see the blood vessels in your own eyes. But researchers demanding a closer look have been working on ways to visualise the full complex network of vessels that permeate our eyeballs. Previous genetic and experimental attempts in mice have tended to look at one sub-section of vessels at a time. A new approach has represented the complete vasculature of the mouse eye at various stages of development (video, with different sections of vasculature digitally coloured). A process to make the eye material transparent is followed by high resolution microscopy and digital analysis. With this technique, the researchers observed how the iris vasculature (yellow) is remodelled during development just after disconnection from the early supply network. They also analysed the impact of injury on vascularisation, showing the platform’s potential for analysing eye disease impacts and treatments on a whole-eye scale.

Written by Anthony Lewis

Video by Luc Krimpenfort and colleagues

Div. of Vascular Biology, Karolinska Institutet, Department of Medical Biochemistry and Biophysics, Stockholm, Sweden

Video originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in bioRxiv, December 2022 (not peer reviewed)

All Eyes

From antelopes to zebrafish, aardvarks to zebus and all the vertebrates in between – including us – you’ll find rounded eyeballs are a common feature. But how does this shape come about? The precursor to vertebrate eyes is the optic vesicle, a developing tissue with two layers: an outer layer of retinal pigmented epithelium (RPE) and an inner layer of neural retina. Neural retina is known to create mechanical forces that help curve the optic vesicle into an optic cup. Researchers now investigate whether RPE cells also contribute, using zebrafish whose RPE cells are genetically engineered to fluoresce. Live-cell fluorescence microscopy of zebrafish embryos (pictured) revealed RPE cells (green) flattening and stretching out to cover the whole neural retina. Preventing this flattening by adding a chemical that interfered with the cells’ architecture stopped the optic cup from becoming curved. RPE is, therefore, also essential in creating the rounded shape of our eyes.

Written by Lux Fatimathas

Video from work by Tania Moreno-Mármol and colleagues

Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Campus de la Universidad Autónoma de Madrid, Madrid, Spain

Video originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in eLife, September 2021

Picking Out Patterns

Often practical as well as pretty, how do nature’s patterns form? The developing retina inside a fruit fly (Drosophila) eye is studded with photoreceptors, gathering light from the outside world. It acts like a bed of sensors to capture a complete image, so it’s essential that clusters of photoreceptors, known as ommatidia, are evenly spaced in a grid-like pattern. Here researchers use image analysis and computer modelling to show how ommatidia develop in consecutive columns (highlighted in the same colour) – a mixture of mechanical and chemical signals from cells in a previous column coaxes the next line of ommatidia cells to form in the gaps like polka dots. Gradually a wave of development patterns the retina, like curtains being printed (although 10000 times smaller). These simulating techniques could now be used to study patterns in early human tissues, or to predict how pattern-painting morphogenesis may go awry during development.

Written by John Ankers

Video from work by Kevin D Gallagher, Madhav Mani and Richard W Carthew

Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA

Video originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in eLife, January 2022

Optical Design

A newly conceived human embryo’s eyes start to develop around five weeks. Layers of cells fold inwards to create structures called the optic cups. These cells then start to mature and specialise as shown in the image: the green circular object is the developing lens; the white tulip-like region the developing retina; and the surrounding red layer contains protective pigmented cells. Here, scientists have identified a pair of chemicals with opposing gradients of concentration along the optic cup. How concentrated the chemicals are in the cells determines what genes are switched on and this, in turn, defines what type of cell they become. This study shows that the chemical gradients come from genes which are known to be evolutionary similar in humans, flies and even worms – further proof our eyes are not the product of intelligent design.

Written by Julie Webb

Image from work by Revathi Balasubramanian and Xuanyu Min, and colleagues

Department of Ophthalmology, Columbia University, New York, NY, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Science Advances, November 2021

Hey there! Have you ever scrolled through YouTube and come across videos claiming that wearing glasses can actually mess with your eyesight? Sounds a bit alarming, right? I mean, most of us think of glasses as our trusty sidekicks, helping us see the world clearly. So, what’s the deal here? Let’s break down this topic in a way that’s easy to understand and, hopefully, a bit fun. The Common Myth:…