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Updated: May 3, 2026
Mouse Eye Enucleation for Remote High-throughput Phenotyping
Published on: November 19, 2011
Photoreceptor degeneration in two mouse models for congenital stationary night blindness type 2
Hanna Regus-Leidig1, Jenny Atorf2, Andreas Feigenspan1
1Department of Biology, Animal Physiology, FAU Erlangen-Nuremberg, Erlangen, Germany.
Abstract:
Light-dependent conductance changes of voltage-gated Cav1.4 channels regulate neurotransmitter release at photoreceptor ribbon synapses. Mutations in the human CACNA1F gene encoding the α1F subunit of Cav1.4 channels cause an incomplete form of X-linked congenital stationary night blindness (CSNB2). Many CACNA1F mutations are loss-of-function mutations resulting in non-functional Cav1.4 channels, but some mutations alter the channels' gating properties and, presumably, disturb Ca(2+) influx at photoreceptor ribbon synapses. Notably, a CACNA1F mutation (I745T) was identified in a family with an uncommonly severe CSNB2-like phenotype, and, when expressed in a heterologous system, the mutation was shown to shift the voltage-dependence of channel activation, representing a gain-of-function. To gain insight into the pathomechanism that could explain the severity of this disorder, we generated a mouse model with the corresponding mutation in the murine Cacna1f gene (I756T) and compared it with a mouse model carrying a loss-of-function mutation (ΔEx14-17) in a longitudinal study up to eight months of age. In ΔEx14-17 mutants, the b-wave in the electroretinogram was absent, photoreceptor ribbon synapses were abnormal, and Ca(2+) responses to depolarization of photoreceptor terminals were undetectable. In contrast, I756T mutants had a reduced scotopic b-wave, some intact rod ribbon synapses, and a strong, though abnormal, Ca(2+) response to depolarization. Both mutants showed a progressive photoreceptor loss, but degeneration was more severe and significantly enhanced in the I756T mutants compared to the ΔEx14-17 mutants.
Insights
Gain-of-function mutations in Cav1.4 channels (CACNA1F gene) can worsen X-linked congenital stationary night blindness (CSNB2). This study shows a specific mutation (I756T) leads to more severe photoreceptor degeneration in mice than loss-of-function mutations.
Area of Science:
- Neuroscience
- Genetics
- Ophthalmology
Background:
- Voltage-gated Cav1.4 channels are crucial for neurotransmitter release at photoreceptor ribbon synapses.
- Mutations in the CACNA1F gene cause X-linked congenital stationary night blindness (CSNB2).
- Some CACNA1F mutations alter channel function, impacting calcium influx and potentially disease severity.
Purpose of the Study:
- To investigate the pathomechanism underlying a severe CSNB2 phenotype associated with a gain-of-function CACNA1F mutation (I745T).
- To compare the effects of a gain-of-function mutation (I756T) versus a loss-of-function mutation (ΔEx14-17) in murine Cacna1f on photoreceptor function and survival.
Main Methods:
- Generation of mouse models with Cacna1f gain-of-function (I756T) and loss-of-function (ΔEx14-17) mutations.
- Longitudinal study up to eight months of age.
- Assessment of electroretinograms, photoreceptor ribbon synapse structure, and calcium responses in photoreceptor terminals.
Main Results:
- Loss-of-function mutants (ΔEx14-17) showed absent b-waves, abnormal synapses, and undetectable calcium responses.
- Gain-of-function mutants (I756T) exhibited reduced scotopic b-waves, some intact synapses, and abnormal but strong calcium responses.
- Both mutants displayed progressive photoreceptor loss, with significantly more severe degeneration in I756T mutants.
Conclusions:
- Gain-of-function mutations in Cav1.4 channels can lead to a more severe form of CSNB2 than loss-of-function mutations.
- Altered Cav1.4 channel gating, not just loss of function, significantly impacts photoreceptor health and synaptic transmission.
- The I756T mutation exacerbates photoreceptor degeneration, highlighting the critical role of precise channel function in retinal integrity.
