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Jasmine Ashley Lucas, Tiffany M Schmidt; Characterization of ipRGCs during mouse retinal development. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1747.
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© ARVO (1962-2015); The Authors (2016-present)
Melanopsin-expressing, intrinsically photosensitive retinal ganglion cells (ipRGCs) represent a non-canonical class of photoreceptor in the mammalian retina. ipRGCs have been shown to be involved in a number of visual behaviors such as circadian photoentrainment and contrast sensitivity. The ipRGC population is made up of five different subtypes and recent evidence suggests ipRGCs influence retinal development. However, ipRGC properties and functions have not been well-characterized in the developing retina.
We utilized in vitro whole cell patch clamp in retinas from mice that expressed GFP under the melanopsin promoter (Opn4-GFP). ipRGCs were specifically targeted using epifluoresence. We investigated the following postnatal day (P) timepoints : P6, P8, P10, P14, and adult. We measured capacitance, resting membrane potential, and input resistance. We also measured cellular response to light stimuli as well as depolarizing current injection. Neurobiotin tracer was included in pipets and after recording, tissue was fixed and immunolabled for ChAT and SMI32 for subtype identification purposes and further investigation of the morphological properties. Cells were identified based on dendritic stratification and SMI32 immunostaining.
We found that ipRGCs already exhibit unique physiological properties early in development that are similar to their adult properties. To highlight this, the M1 subtype as early as P8 has no significant difference in capacitance (p=0.305), resting membrane potential (p=0.375), input resistance (p=0.759) or the maximum light response (p=0.651) in comparison to its adult counterpart. However, we find that ipRGCs undergo substantial morphological changes as they mature, reaching adult morphology sometime after P14.
We find that even early in postnatal retinal development, ipRGC subtypes have similar physiological properties when compared to their adult counterparts although their morphological features do not reach maturity until after eye opening (P14). Understanding these differences will provide insight into the potential influence of individual ipRGC subtypes on retinal development.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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