i) Scientific basis:
The neuronal processing that enables us to see and recognise complex visual images like text and faces starts in the retina itself. Diseases leading to photoreceptor death cause irreversible sight loss and, eventually, blindness, and yet the rest of the inner retinal circuitry remains largely intact; this presents the opportunity to restore vision, by transplanting healthy donor photoreceptors that might form new synaptic connections with the remaining retina. We have recently provided crucial proof-of-concept for this approach, transplanting human pluripotent stem cell (hPSC)-derived cone photoreceptors into a mouse model of advanced retinal disease (Ribeiro et al., 2021). Importantly, donor photoreceptors formed new connections in numbers sufficient to drive neuronal and behavioural responses to a simple light stimulus (light flash). However, it is not yet known how accurately these new connections reflect the normal wiring of the retina, or if the retina is able to process more complex visual stimuli. Here, you will take a structure/function approach to map the physical circuitry achieved between donor photoreceptors and host bipolar neurons and combine this with electrophysiological assessments of retinal function.
1) Using multiple synaptic tracing and high resolution imaging techniques, map the neuronal connectome established following photoreceptor transplantation in a model of retinal disease and compare this to that of the healthy and untreated diseased retina.
2) Using electrophysiological recordings, investigate how the physical connectivity established in (1) relates to the retinal processing (types of response) of visual stimuli.
human stem cell retinal organoid cultures; transplantation; synaptic labelling and tracing techniques; histology; electrophysiology including multi-electrode arrays
Y1: Learn techniques and make synaptic tracing tools, transplantation
Y2: Map the anatomical connectome of transplanted, compared to normal and diseased retina
Y3: Establish electrophysiological basis of rescue, compared to physical connectome