Populations of neurons vary in their demographics: They differ in their absolute numbers, in their intercellular spacing and the patterning this produces, in their degree of dendritic overlap and its regulation, and in their synaptic connectivity and the convergence ratios associated with their afferent neurons. The present research program has been addressing the causal relationships associated with such neuronal population dynamics, using the retina as a model system and working with a panel of twenty-six genetically distinct recombinant inbred (RI) mouse strains. Neuron number has been shown to vary considerably across these strains of mice, for twelve different classes of retinal neuron, and this variation maps to discrete genomic loci (quantitative trait loci, or QTL) for each cell type, showing minimal evidence for genomic co-regulation. The genetic sources of this variation in neuron number will be defined, for each cell type, and the developmental roles of these genes modulating cell number will be identified. Independent of neuron number, neurons vary in other histotypical features across these RI strains, including the orderliness by which they space themselves apart within a layer. The population of horizontal cells is one such example, where variation in the orderliness of their patterning maps to two narrow genomic loci. Causal genes and their variants at these loci will be pursued, and comparable spatial statistical analysis will be conducted for the other cell types to map QTL in pursuit of the genetic determinants of neuronal spacing. The consequence of such independent variation in the number of afferent and target neurons upon dendritic differentiation will also be examined, using the AII amacrine cell to explore the unique independent control of its lobular versus dendritic growth. Finally, a role for the transcription factor Sox2 in cholinergic amacrine cells has recently been demonstrated, causing a mis- positioning of these amacrine cells between the inner nuclear layer and ganglion cell layer, and a conversion of their mono-stratifying dendrites into a bi-stratifying morphology. The role of Sox2 will be further explored to identify the downstream genes responsible for these altered cholinergic amacrine cell traits, by transcriptome- profiling of purified cholinergic amacrine cells from Sox2-deficient versus control retinas. The present research proposal will thereby identify the genetic determinants and intercellular interactions that underlie the demographic features of neuronal populations in the retina, clarifying our understanding of retinal development, as well as identifying genetic variants that may contribute to retinal disease.

Public Health Relevance

This research program will identify the genetic determinants controlling the variation in neuron number, laminar positioning and intercellular spacing using the retina as a model system. It will define the cellular interactions and molecular regulation governing neuronal differentiation, including dendritic outgrowth, branching and stratification. These studies will clarify the developmental processes and underlying mechanisms that produce the functional architecture and connectivity of the mature retina. This research will, consequently, contribute to our understanding of developmental disorders of the nervous system, and provide a knowledge base for the emerging field of neural regenerative medicine.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
3R01EY019968-08S1
Application #
9700995
Study Section
Program Officer
Greenwell, Thomas
Project Start
2010-01-01
Project End
2019-12-31
Budget Start
2018-07-01
Budget End
2018-12-31
Support Year
8
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of California Santa Barbara
Department
Miscellaneous
Type
Organized Research Units
DUNS #
094878394
City
Santa Barbara
State
CA
Country
United States
Zip Code
93106
Kautzman, Amanda G; Keeley, Patrick W; Borhanian, Sarra et al. (2018) Genetic Control of Rod Bipolar Cell Number in the Mouse Retina. Front Neurosci 12:285
Keeley, Patrick W; Reese, Benjamin E (2018) DNER and NFIA are expressed by developing and mature AII amacrine cells in the mouse retina. J Comp Neurol 526:467-479
Kautzman, Amanda G; Keeley, Patrick W; Nahmou, Michael M et al. (2018) Sox2 regulates astrocytic and vascular development in the retina. Glia 66:623-636
Kautzman, Amanda G; Keeley, Patrick W; Ackley, Caroline R et al. (2018) Xkr8 Modulates Bipolar Cell Number in the Mouse Retina. Front Neurosci 12:876
Reese, Benjamin E (2018) Axon Terminal Arbors of Retinal Horizontal Cells Lose Control. Front Neural Circuits 12:82
Sankaran, Mathangi; Keeley, Patrick W; He, Li et al. (2018) Dopaminergic amacrine cell number, plexus density, and dopamine content in the mouse retina: Strain differences and effects of Bax gene disruption. Exp Eye Res 177:208-212
Keeley, Patrick W; Reese, Benjamin E (2018) The somal patterning of the AII amacrine cell mosaic in the mouse retina is indistinguishable from random simulations matched for density and constrained by soma size. Vis Neurosci 35:E003
Stincic, Todd L; Keeley, Patrick W; Reese, Benjamin E et al. (2018) Bistratified starburst amacrine cells in Sox2 conditional knockout mouse retina display ON and OFF responses. J Neurophysiol 120:2121-2129
Keeley, Patrick W; Whitney, Irene E; Reese, Benjamin E (2017) Genomic Control of Retinal Cell Number: Challenges, Protocol, and Results. Methods Mol Biol 1488:365-390
Puller, Christian; Arbogast, Patrick; Keeley, Patrick W et al. (2017) Dendritic stratification differs among retinal OFF bipolar cell types in the absence of rod photoreceptors. PLoS One 12:e0173455

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