Dataset Information

The Ciliopathy Gene ahi1 Is Required for Zebrafish Cone Photoreceptor Outer Segment Morphogenesis and Survival.

ABSTRACT:

Purpose

Joubert syndrome (JBTS) is an autosomal recessive ciliopathy with considerable phenotypic variability. In addition to central nervous system abnormalities, a subset of JBTS patients exhibit retinal dystrophy and/or kidney disease. Mutations in the AHI1 gene are causative for approximately 10% of all JBTS cases. The purpose of this study was to generate ahi1 mutant alleles in zebrafish and to characterize the retinal phenotypes.

Methods

Zebrafish ahi1 mutants were generated using transcription activator-like effector nucleases (TALENs). Expression analysis was performed by whole-mount in situ hybridization. Anatomic and molecular characterization of photoreceptors was investigated by histology, electron microscopy, and immunohistochemistry. The optokinetic response (OKR) behavior assay was used to assess visual function. Kidney cilia were evaluated by whole-mount immunostaining.

Results

The ahi1lri46 mutation in zebrafish resulted in shorter cone outer segments but did not affect visual behavior at 5 days after fertilization (dpf). No defects in rod morphology or rhodopsin localization were observed at 5 dpf. By 5 months of age, cone degeneration and rhodopsin mislocalization in rod photoreceptors was observed. The connecting cilium formed normally and Cc2d2a and Cep290 localized properly. Distal pronephric duct cilia were absent in mutant fish; however, only 9% of ahi1 mutants had kidney cysts by 5 dpf, suggesting that the pronephros remained largely functional.

Conclusions

The results indicate that Ahi1 is required for photoreceptor disc morphogenesis and outer segment maintenance in zebrafish.

SUBMITTER: Lessieur EM

PROVIDER: S-EPMC5270624 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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Publications

The Ciliopathy Gene ahi1 Is Required for Zebrafish Cone Photoreceptor Outer Segment Morphogenesis and Survival.

Lessieur Emma M EM Fogerty Joseph J Gaivin Robert J RJ Song Ping P Perkins Brian D BD

Investigative ophthalmology & visual science 20170101 1

<h4>Purpose</h4>Joubert syndrome (JBTS) is an autosomal recessive ciliopathy with considerable phenotypic variability. In addition to central nervous system abnormalities, a subset of JBTS patients exhibit retinal dystrophy and/or kidney disease. Mutations in the AHI1 gene are causative for approximately 10% of all JBTS cases. The purpose of this study was to generate ahi1 mutant alleles in zebrafish and to characterize the retinal phenotypes.<h4>Methods</h4>Zebrafish ahi1 mutants were generated ...[more]

PMID: 28118669

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Project description:C8ORF37 is a causative gene for three different clinical forms of incurable retinal degeneration. However, the completely unknown function of C8ORF37 limits our understanding of the pathogenicity of C8ORF37 mutations. Here, we performed a comprehensive phenotypic characterization of a C8orf37 KO mouse line, generated using CRISPR/Cas9 technology. Both C8orf37 KO male and female mice exhibited progressive and simultaneous degeneration of rod and cone photoreceptors but no non-ocular phenotypes. The major ultrastructural feature of C8orf37 KO photoreceptors was massive disorganization of the outer segment (OS) membrane discs starting from the onset of disc morphogenesis during development. At the molecular level, the amounts of multiple OS-specific membrane proteins, including proteins involved in membrane disc organization, were reduced, although these proteins were targeted normally to the OS. Considering the distribution of C8ORF37 throughout the photoreceptor cell body, the normal structure of the KO photoreceptor connecting cilium, and the absence of defects in other ciliary organs of the KO mice, our findings do not support the previous notion that C8ORF37 was a ciliary protein. Because C8ORF37 is absent in the photoreceptor OS, C8ORF37 may participate in the secretory pathway of OS membrane proteins in the photoreceptor cell body and thus maintain the homeostasis of these proteins. This study established a valid animal model for future therapeutic studies of C8ORF37-associated retinal degeneration. This study also shed new light on the role of C8ORF37 in photoreceptors and on the pathogenic mechanism underlying retinal degeneration caused by C8ORF37 mutations.SIGNIFICANCE STATEMENT Inherited retinal degeneration is a group of incurable conditions with poorly understood underlying molecular mechanisms. We investigated C8ORF37, a causative gene for three retinal degenerative conditions: retinitis pigmentosa, cone-rod dystrophy, and Bardet-Biedl syndrome. C8ORF37 encodes a protein with no known functional domains and thus its biological function is unpredictable. We knocked out the C8ORF37 ortholog in mice, which resulted in a retinal phenotype similar to that observed in patients. We further demonstrated that C8ORF37 is required for photoreceptor outer segment disc formation and alignment, a process that is critical for photoreceptor function and survival. This study advances our understanding of the pathogenesis of retinal degeneration and establishes a valuable mouse model for future therapeutic development.

Dataset Information

The Ciliopathy Gene ahi1 Is Required for Zebrafish Cone Photoreceptor Outer Segment Morphogenesis and Survival.

Purpose

Methods

Results

Conclusions

Publications

The Ciliopathy Gene ahi1 Is Required for Zebrafish Cone Photoreceptor Outer Segment Morphogenesis and Survival.

Similar Datasets

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