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Updated: Jun 13, 2026
Imaging Ca2+ Dynamics in Cone Photoreceptor Axon Terminals of the Mouse Retina
Published on: May 6, 2015
Characterization of Ca2+ signalling in postnatal mouse retinal ganglion cells: involvement of OPA1 in Ca2+ clearance
Govindan Dayanithi1, Murielle Chen-Kuo-Chang, Cedric Viero
1Institut des Neurosciences de Montpellier, INSERM U583, Montpellier, France.
Purpose:
The regulation of Ca(2+) entry and removal is a fine-tuned process which remains not well understood in mouse retinal ganglion cells (RGCs). The latter are known to be sensitive to dysfunctions of mitochondria, organelles playing a pivotal role in Ca(2+) reuptake.
Methods:
We first described the Ca(2+) signals of RGCs in response to varied drugs with Fura-2 imaging, and secondly tested the role of optic atrophy 1 or OPA1, the gene responsible for Autosomal Dominant Optic Atrophy, on mitochondrial ability to capture intracellular Ca(2+) in cells transfected with the OPA1 small interfering ribonucleic acids (siRNAs).
Results:
In control RGCs, K(+)-evoked [Ca(2+)](i) increase was blocked by the Ca(2+) channel antagonists (Ni(2+)+ Cd(2+)) and GABA(A) receptor agonist muscimol-induced [Ca(2+)](i) responses were attenuated by the GABA(A) receptor antagonists, picrotoxin and gabazine. We also prove the presence of NMDA and AMPA/Kainate (glutamate receptor agonists) responsive receptors in this model. Application of cyclopiazonic acid, an inhibitor of Ca(2+)-ATPase pumps of the intracellular Ca(2+) stores, induced an increase in [Ca(2+)](i) while ryanodine or caffeine had no effect on resting [Ca(2+)](i). Spontaneous Ca(2+) oscillations in contacting neurons highlighted the importance of cross-talks between RGCs during maturation. The mitochondrial respiration uncoupler, carbonyl cyanide 3-chlorophenylhydrazone (CCCP), induced robust raises of intracellular Ca(2+) after K(+) application, with a more pronounced effect in cells silenced for OPA1, which could lead to cell death.
Conclusions:
Our results indicate an important role of OPA1 in mitochondrial dependent Ca(2+) homeostasis and cell survival in RGCs, suggesting a possible patho-physiological mechanism involved in inherited optic neuropathies.
Insights
Optic Atrophy 1 (OPA1) is crucial for calcium homeostasis and survival in retinal ganglion cells (RGCs). OPA1 dysfunction impairs mitochondrial calcium uptake, potentially causing cell death and contributing to optic neuropathies.
Area of Science:
- Neuroscience
- Cell Biology
- Ophthalmology
Background:
- Calcium (Ca2+) signaling is vital for neuronal function but its precise regulation in mouse retinal ganglion cells (RGCs) is not fully understood.
- Mitochondria play a critical role in intracellular Ca2+ buffering, and their dysfunction is implicated in RGC sensitivity and optic neuropathies.
Purpose of the Study:
- To elucidate the mechanisms of Ca2+ entry and removal in mouse RGCs.
- To investigate the role of Optic Atrophy 1 (OPA1) in mitochondrial Ca2+ handling and RGC survival.
Main Methods:
- Utilized Fura-2 imaging to characterize Ca2+ signals in RGCs under various drug treatments.
- Employed small interfering ribonucleic acids (siRNAs) to silence OPA1 expression and assess its impact on mitochondrial Ca2+ uptake.
Main Results:
- Identified specific ion channels and receptors (e.g., GABA(A), NMDA, AMPA/Kainate) involved in Ca2+ signaling in RGCs.
- Demonstrated that OPA1 silencing exacerbates intracellular Ca2+ increases induced by mitochondrial uncouplers, leading to cell death.
- Observed spontaneous Ca2+ oscillations between RGCs, indicating intercellular communication during development.
Conclusions:
- OPA1 is essential for maintaining mitochondrial-dependent Ca2+ homeostasis in RGCs.
- Dysregulation of OPA1 impacts RGC survival, suggesting a potential mechanism underlying inherited optic neuropathies.
