The Heterogeneity of intrinsically photosensitive Retinal Ganglion Cells

(ipRGCs)

Ben Loreto & Kris Cronise

OutlineipRGCsFunctionHeterogeneity of ipRGCsAnatomy and PhysiologyModelFuture GoalsReferences and

Acknowledgements

ipRGCsClassical

Photoreceptors (rods and cones)

Horizontal Cells,Bipolar Cells,

And Amacrine Cells

Ganglion Cells

ipRGCs = intrinically photosensitive retinal

ganglion cells

Source: http://www.skidmore.edu/~hfoley/images/Retina.jpg

Melanopsin Amination here

Heterogeneity of ipRGCs5 major classes of

ipRGCs

Each classified by certain differences in anatomy and physiology

Adapted from: http://www.nature.com/nature/journal/v415/n6871/images/415493a-f1.2.jpg

Soma SizeSoma size = Size of cell body

Both figures modified from: Schmidt et al. (2011)

Dendritic Stratification and FieldDendritic Stratification = Where signal is received in the retinaDendritic field = Amount of area covered by dendrites

Both figures modified from: Ecker. (2011)

Molecular IdentityMolecular Identity = Level of Gene ExpressionMelanopsin gene = e.g. Opn4

Both figures modified from: Schmidt et al. (2011)

Intrinsic Light ResponseEvaluation of response to

light

Traits include sensitivity based on both size of peak and duration

Modified from: Schmidt et al (2011)

Role in VisionRods and Cones = IF

Vision

ipRGCs = NIF Vision

Adapted from: http://www.photobiology.info/Sengupta.html

What Has Been DoneMethods:•Chemical reactions based on hypothesized pathway

Example:

•Conversion of chemical reactions to differential equations using mass action (and Michaelis-Menten kinetics)

Example:

•System of differential equations was solved in Matlab and the solution for the concentration of open channels was plotted

•Parameters (rate constants) were adjusted to fit experimental data with the help of MATLAB function fminunc.

What Has Been DoneResults: Note: Response of M1 cells

afff Electrophysiological data obtained from Jess and Abby Electrophysiological data obtained from R.L. Brown

What We’re Doing

Further DirectionsComplete literature review of non-M1 ipRGCs

Compile differences among different ipRGC classes

Incorporate those differences into the model

ReferencesReferences:Schmidt. "Melanopsin-Positive Intrinsically Photosensitive Retinal Ganglion Cells: From Form to Function." The Journal of Neuroscience, 9 Nov. 2011. Web. 20 Oct. 2014.Wong. "Photoresponse Diversity among the Five Types of Intrinsically Photosensitive Retinal Ganglion Cells." The Journal of Physiology, 3 Feb. 2014. Web. 20 Oct. 2014.Hattar et al. "Melanopsin-Expressing Retinal Ganglion-Cell Photoreceptors: Cellular Diversity and Role in Pattern Vision." Neuron (2010): 49-60. Print.

AcknowledgementsWe would like to thank:

UBM @ UMBCDrs. Phyllis Robinson Kathleen Hoffman, and Hye-Won KangAbigail Jackson and Jessica OrtegaPrevious CohortsThe Robinson Lab and its collaboratorsNSF