Guest post by Matthew W. Self – Netherlands Institute for Neuroscience, Amsterdam
The human retina has a small region called the ‘fovea’ in which all the cone photoreceptors are packed closely together. The fovea provides by far the highest spatial resolution of the retina and we use this region of the retina for all our daytime detailed vision (e.g. reading, recognizing faces). Humans and other primates move their eyes around 3 times per second to point their foveas at interesting locations in the visual world. We essentially build-up a detailed view of the world by ‘scanning’ it with our foveas.
Recently interest in mouse vision has exploded as scientists put to use the sophisticated genetic tools that are available in mice to try to understand vision. The kind of rapid eye-movement scanning found in primates is largely absent from mice. The mouse retina doesn’t have a fovea and is thought to be uniformly sensitive to light. The question then arises whether mice have any spatial biases in their vision – do they have a ‘hot-spot’ in which vision is more detailed, as we do?
We addressed this question by mapping the responses of the visual cortex of mice to visual images. We used a mouse genetic line in which a fluorescent calcium indicator (GCaMP) is present in all neurons in cortex. GCaMP increases in fluorescence when cells become active, allowing us to map out which parts of the brain respond to different regions of the visual world under a microscope. To measure the resolution of vision we measured the ‘population receptive field’ or pRF at different points in the brain. The size of the pRF tells us how accurate the representation of the visual world is; brain regions with large pRFs have only a coarse representation of space, whereas regions with small pRFs have a very detailed view. Surprisingly we found that mouse visual cortex contains a region in which the pRFs are 50% smaller than the rest of the brain. In this region brain cells respond to more closely packed parts of the visual world and can therefore build up a more detailed picture of the world. This region responded to visual stimuli placed directly in front of the mouse and slightly above it, suggesting that mice, like primates, also have a visual hot-spot that they could use to see the world in more detail. This result provides more support for the use of the mouse as a model of human vision.
SfN poster: Sunday 4th, 13:00 – 17:00; board no. CC9 219.18
We are excited to be attending the the SfN 2018 Annual Meeting in San Diego starting this weekend. We are looking forward to engaging with researchers and to raising awareness of the IMPC as a resource. If you are attending the conference and want to learn more about the IMPC please visit stand 4132.
We will be tweeting relevant research and news during the conference so please follow us on Twitter for updates. We are also adding guest blog posts from attendees presenting research that utilize mouse models. As well as documentation and information about our latest research, we will also be giving out coasters, pens, notebooks and toy mice. Please don’t hesitate to come to our stand if you are interested in hearing more about the IMPC!
What is the International Mouse Phenotyping Consortium?
The International Mouse Phenotyping Consortium (IMPC) is an international effort to identify the function of every gene in the mouse genome. The entire genome of many species has now been published and whole genome sequencing is becoming relatively quick and cheap to complete. Despite these advancements the function of the majority of genes remains unknown.
This is where the IMPC comes in, with the goal of phenotyping all 20,000 or so protein coding mouse genes. To achieve this, genes in the mouse genome are switched off then standardised physiological tests undertaken across a range of biological systems. This data is then made freely available to the research community. As well as completing large scale comparative studies, the overall aim of the project is to create a platform for this data where researchers/clinicians can search for genes or diseases of interest to help them understand human health and disease.
IMPC data can be used in a variety of ways, such as to investigate basic biology mechanisms that can lead to new therapeutic targets or to narrow down a suspected list of genes in patients. In the last few years the IMPC have made major discoveries in parts of the genome that were hitherto unexplored, with new genes discovered relating to areas such as deafness, diabetes, and rare diseases. Summaries of five recent research articles that highlight the diversity of how IMPC data can be used are listed below.
- Advancements in mouse phenomics and its uses for inferring mammalian gene function
- Novel hearing loss genes identified in large study by scientists across the world
- New diabetes genes discovered in latest IMPC research
- Study of unprecedented size reveals how sex ‘blindspot’ could misdirect medical research
- New research suggests laboratory mouse data can help in wildlife conservation
More information on the objectives and background of the IMPC can be found on our main website: https://www.mousephenotype.org/objectives-and-background