Spatial Expression Pattern of the Major Ca2+-Buffer Proteins in Mouse Retinal Ganglion Cells.

Tamás Kovács-Öller,Ádám J Tengölics,Miklós Nyitrai,Alma Ganczer,Edina Szabó-Meleg,Boglárka Balogh,Gergely Szarka,Béla Völgyi

doi:10.3390/cells9040792

Tamás Kovács-Öller, Ádám J Tengölics + Show 6 more

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https://doi.org/10.3390/cells9040792

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Journal: Cells	Publication Date: Mar 25, 2020
Citations: 11	License type: CC BY 4.0

Affiliation: University of Pecs, Hungarian Academy of Sciences

Abstract

The most prevalent Ca2+-buffer proteins (CaBPs: parvalbumin—PV; calbindin—CaB; calretinin—CaR) are widely expressed by various neurons throughout the brain, including the retinal ganglion cells (RGCs). Even though their retinal expression has been extensively studied, a coherent assessment of topographical variations is missing. To examine this, we performed immunohistochemistry (IHC) in mouse retinas. We found variability in the expression levels and cell numbers for CaR, with stronger and more numerous labels in the dorso-central area. CaBP+ cells contributed to RGCs with all soma sizes, indicating heterogeneity. We separated four to nine RGC clusters in each area based on expression levels and soma sizes. Besides the overall high variety in cluster number and size, the peripheral half of the temporal retina showed the greatest cluster number, indicating a better separation of RGC subtypes there. Multiple labels showed that 39% of the RGCs showed positivity for a single CaBP, 30% expressed two CaBPs, 25% showed no CaBP expression, and 6% expressed all three proteins. Finally, we observed an inverse relation between CaB and CaR expression levels in CaB/CaR dual- and CaB/CaR/PV triple-labeled RGCs, suggesting a mutual complementary function.

Highlights

Vision is the most important perception modality for humans, it is still not entirely known how the Ca2+ homeostasis of neurons in the visual signaling axis is controlled by the various neuronal Ca2+ -buffer proteins (CaBPs)
We present PV, CaR, and CaB expression in the same subset of neurons for the first time, which allows a direct comparison of the expression levels of the three CaBPs in mouse retinal
We found that expression levels of PV and CaB were rather homogenous across retinal regions, confirming our qualitative observations

Summary

Introduction

Vision is the most important perception modality for humans, it is still not entirely known how the Ca2+ homeostasis of neurons in the visual signaling axis is controlled by the various neuronal Ca2+ -buffer proteins (CaBPs). One of the most extensively studied brain loci in this regard is the mammalian retina where expression of CaBPs has been described in many different neuron populations of various model animals [1] and in a human specimen [2]. The diverse coding mechanism each RGC subtype performs is heavily determined by a unique composition of intracellular molecules. Some of these molecules, like CaBPs, can be utilized as markers for one or multiple distinct cell groups. We used the gaussian mixture model (GMM) clustering method (described in more detail under the Clustering paragraph) to determine the background level, the non-expressing cells could be excluded from further analyses

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