Zebrafish as a Model to Evaluate a CRISPR/Cas9-Based Exon Excision Approach as a Future Treatment Option for EYS-Associated Retinitis Pigmentosa

Retinitis pigmentosa (RP) is an inherited retinal disease (IRD) with an overall prevalence of 1 in 4000 individuals. Mutations in EYS (Eyes shut homolog) are among the most frequent causes of non-syndromic autosomal recessively inherited RP and act via a loss-of-function mechanism. In light of the recent successes for other IRDs, we investigated the therapeutic potential of exon skipping for EYS-associated RP. CRISPR/Cas9 was employed to generate zebrafish from which the region encompassing the orthologous exons 37-41 of human EYS (eys exons 40-44) was excised from the genome. The excision of these exons was predicted to maintain the open reading frame and to result in the removal of exactly one Laminin G and two EGF domains. Although the eysΔexon40-44 transcript was found at levels comparable to wild-type eys, and no unwanted off-target modifications were identified within the eys coding sequence after single-molecule sequencing, EysΔexon40-44 protein expression could not be detected. Visual motor response experiments revealed that eysΔexon40-44 larvae were visually impaired and histological analysis revealed a progressive degeneration of the retinal outer nuclear layer in these zebrafish. Altogether, the data obtained in our zebrafish model currently provide no indications for the skipping of EYS exons 37-41 as an effective future treatment strategy for EYS-associated RP.

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Pathogenic STX3 variants affecting the retinal and intestinal transcripts cause an early-onset severe retinal dystrophy in microvillus inclusion disease subjects

Human Genetics ◽

10.1007/s00439-021-02284-1 ◽

2021 ◽

Author(s):

Andreas R. Janecke ◽

Xiaoqin Liu ◽

Rüdiger Adam ◽

Sumanth Punuru ◽

Arne Viestenz ◽

...

Keyword(s):

Early Onset ◽

Single Nucleotide Polymorphism Array ◽

Outer Nuclear Layer ◽

Retinal Dystrophy ◽

Geographic Origin ◽

Retinal Disease ◽

Homozygosity Mapping ◽

Rod Photoreceptor ◽

Loss Of Function ◽

Knockout Mouse Model

AbstractBiallelic STX3 variants were previously reported in five individuals with the severe congenital enteropathy, microvillus inclusion disease (MVID). Here, we provide a significant extension of the phenotypic spectrum caused by STX3 variants. We report ten individuals of diverse geographic origin with biallelic STX3 loss-of-function variants, identified through exome sequencing, single-nucleotide polymorphism array-based homozygosity mapping, and international collaboration. The evaluated individuals all presented with MVID. Eight individuals also displayed early-onset severe retinal dystrophy, i.e., syndromic—intestinal and retinal—disease. These individuals harbored STX3 variants that affected both the retinal and intestinal STX3 transcripts, whereas STX3 variants affected only the intestinal transcript in individuals with solitary MVID. That STX3 is essential for retinal photoreceptor survival was confirmed by the creation of a rod photoreceptor-specific STX3 knockout mouse model which revealed a time-dependent reduction in the number of rod photoreceptors, thinning of the outer nuclear layer, and the eventual loss of both rod and cone photoreceptors. Together, our results provide a link between STX3 loss-of-function variants and a human retinal dystrophy. Depending on the genomic site of a human loss-of-function STX3 variant, it can cause MVID, the novel intestinal-retinal syndrome reported here or, hypothetically, an isolated retinal dystrophy.

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suz12 inactivation in p53- and nf1-deficient zebrafish accelerates the onset of malignant peripheral nerve sheath tumors and expands the spectrum of tumor types

Disease Models & Mechanisms ◽

10.1242/dmm.042341 ◽

2020 ◽

Vol 13 (8) ◽

pp. dmm042341 ◽

Cited By ~ 1

Author(s):

Felix Oppel ◽

Dong H. Ki ◽

Mark W. Zimmerman ◽

Kenneth N. Ross ◽

Ting Tao ◽

...

Keyword(s):

Peripheral Nerve ◽

Chromatin Modification ◽

Control Fish ◽

Loss Of Function ◽

Zebrafish Model ◽

Reading Frame ◽

Nerve Sheath Tumors ◽

Peripheral Nerve Sheath Tumors ◽

Nerve Sheath ◽

Tumor Types

ABSTRACTPolycomb repressive complex 2 (PRC2) is an epigenetic regulator of gene expression that possesses histone methyltransferase activity. PRC2 trimethylates lysine 27 of histone H3 proteins (H3K27me3) as a chromatin modification associated with repressed transcription of genes frequently involved in cell proliferation or self-renewal. Loss-of-function mutations in the PRC2 core subunit SUZ12 have been identified in a variety of tumors, including malignant peripheral nerve sheath tumors (MPNSTs). To determine the consequences of SUZ12 loss in the pathogenesis of MPNST and other cancers, we used CRISPR-Cas9 to disrupt the open reading frame of each of two orthologous suz12 genes in zebrafish: suz12a and suz12b. We generated these knockout alleles in the germline of our previously described p53 (also known as tp53)- and nf1-deficient zebrafish model of MPNSTs. Loss of suz12 significantly accelerated the onset and increased the penetrance of MPNSTs compared to that in control zebrafish. Moreover, in suz12-deficient zebrafish, we detected additional types of tumors besides MPNSTs, including leukemia with histological characteristics of lymphoid malignancies, soft tissue sarcoma and pancreatic adenocarcinoma, which were not detected in p53/nf1-deficient control fish, and are also contained in the human spectrum of SUZ12-deficient malignancies identified in the AACR Genie database. The suz12-knockout tumors displayed reduced or abolished H3K27me3 epigenetic marks and upregulation of gene sets reported to be targeted by PRC2. Thus, these zebrafish lines with inactivation of suz12 in combination with loss of p53/nf1 provide a model of human MPNSTs and multiple other tumor types, which will be useful for mechanistic studies of molecular pathogenesis and targeted therapy with small molecule inhibitors.

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X-Linked Retinitis Pigmentosa Caused by Non-Canonical Splice Site Variants in RPGR

International Journal of Molecular Sciences ◽

10.3390/ijms22020850 ◽

2021 ◽

Vol 22 (2) ◽

pp. 850

Author(s):

Friederike Kortüm ◽

Sinja Kieninger ◽

Pascale Mazzola ◽

Susanne Kohl ◽

Bernd Wissinger ◽

...

Keyword(s):

Retinitis Pigmentosa ◽

Splice Site ◽

Exon Skipping ◽

Open Reading Frame ◽

Aberrant Splicing ◽

Reading Frame ◽

Pathogenic Variants ◽

Nucleotide Addition ◽

Intron 2

We aimed to validate the effect of non-canonical splice site variants in the RPGR gene in five patients from four families diagnosed with retinitis pigmentosa. Four variants located in intron 2 (c.154 + 3_154 + 6del), intron 3 (c.247 + 5G>A), intron 7 (c.779-5T>G), and intron 13 (c.1573-12A>G), respectively, were analyzed by means of in vitro splice assays. Splicing analysis revealed different aberrant splicing events, including exon skipping and intronic nucleotide addition, which are predicted to lead either to an in-frame deletion affecting relevant protein domains or to a frameshift of the open reading frame. Our data expand the landscape of pathogenic variants in RPGR, thereby increasing the genetic diagnostic rate in retinitis pigmentosa and allowing patients harboring the analyzed variants to be enrolled in clinical trials.

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Retinitis Pigmentosa Is Associated With Shifts in The Gut Microbiome

10.21203/rs.3.rs-107256/v1 ◽

2020 ◽

Author(s):

Oksana Kutsyr ◽

Lucía Maestre-Carballa ◽

Mónica Lluesma-Gomez ◽

Manuel Martinez-Garcia ◽

Nicolás Cuenca ◽

...

Keyword(s):

Retinitis Pigmentosa ◽

Gut Microbiome ◽

Outer Nuclear Layer ◽

Functional Decline ◽

Retinal Disease ◽

Rrna Gene ◽

Sequencing Data ◽

Cell Reactivity ◽

Alpha And Beta Diversity ◽

Potential Biomarker

Abstract Background: The gut microbiome is known to influence the pathogenesis and progression of neurodegenerative diseases. However, there has been relatively little focus upon the implications of the gut microbiome in retinal diseases such as retinitis pigmentosa (RP) that leads to photoreceptor degeneration and is the main worldwide cause of complete blindness in adulthood. Here, we investigated changes in gut microbiome composition linked to RP, by assessing both retinal degeneration and gut microbiome in the rd10 mouse model of RP as compared to control C57BL/6J mice.Results: In rd10 mice, retinal responsiveness to flashlight stimuli was deteriorated with respect to observed in age-matched control mice, with decreased amplitudes in the a- and b-wave responses of the electroretinogram and concomitant reduction of the visual acuity. This functional decline in dystrophic animals was accompanied by photoreceptor loss, evidenced by decreased outer nuclear layer thickness, and morphologic anomalies in photoreceptor cells. Changes in retinal neurons were paralleled to induction of reactive gliosis in retina, with increased microglial cell numbers and higher Müller cell reactivity in rd10 mice. Furthermore, 16S rRNA gene amplicon sequencing data showed a microbial gut dysbiosis with differences in alpha and beta diversity at the genera, species and amplicon sequence variants (ASV) levels between dystrophic and control mice. A taxonomic partitioning of ASV was observed since unique ASVs present in only one group had a cumulative relative microbial abundance between 17.6% (rd10 mice) and 26.7% (C57BL/6J mice). Remarkably, four fairly common ASV in healthy gut microbiome belonging to -Rikenella spp., Muribaculaceace spp., Prevotellaceae UCG-001 spp., and Bacilli spp.- were absent in the gut microbiome of retinal disease mice, while Bacteroides caecimuris was significantly enriched in mice with retinitis pigmentosa. Conclusions: Our results indicate that retinal degenerative changes in retinitis pigmentosa are linked to relevant gut microbiome changes. The findings suggest that microbiome shifting could be considered as potential biomarker and therapeutic target for retinal degenerative diseases.

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Modelling and rescue of RP2 Retinitis Pigmentosa using iPSC Derived Retinal Organoids

10.1101/2020.01.28.923227 ◽

2020 ◽

Cited By ~ 1

Author(s):

Amelia Lane ◽

Katarina Jovanovic ◽

Ciara Shortall ◽

Daniele Ottaviani ◽

Anna Brugulat Panes ◽

...

Keyword(s):

Cell Death ◽

Retinitis Pigmentosa ◽

Photoreceptor Cell ◽

Outer Nuclear Layer ◽

Disease Model ◽

Retinal Disease ◽

Severe Form ◽

Rod Photoreceptor ◽

Knock Out ◽

Induced Pluripotent

SummaryRP2 mutations cause a severe form of X-linked retinitis pigmentosa (XLRP). The mechanism of RP2 associated retinal degeneration in humans is unclear, and animal models of RP2 XLRP do not recapitulate this severe phenotype. Here, we developed gene edited isogenic RP2 knock-out (RP2 KO) induced pluripotent stem cells (iPSC) and RP2 patient derived iPSC to produce 3D retinal organoids as a human retinal disease model. Strikingly, the RP2 KO and RP2 patient derived organoids showed a peak in rod photoreceptor cell death at day 150 (D150) with subsequent thinning of the organoid outer nuclear layer (ONL) by D180 of culture. AAV mediated gene augmentation with human RP2 rescued the degeneration phenotype of the RP2 KO organoids, to prevent ONL thinning and restore rhodopsin expression. Notably, these data show that 3D retinal organoids can be used to model photoreceptor degeneration and test potential therapies to prevent photoreceptor cell death.

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Antisense oligonucleotide-based treatment of retinitis pigmentosa caused by mutations in USH2A exon 13

10.1101/2020.10.06.320499 ◽

2020 ◽

Author(s):

Ralph Slijkerman ◽

Hester van Diepen ◽

Silvia Albert ◽

Margo Dona ◽

Hanka Venselaar ◽

...

Keyword(s):

Retinitis Pigmentosa ◽

Antisense Oligonucleotide ◽

Antisense Oligonucleotides ◽

Outer Nuclear Layer ◽

Exon Skipping ◽

Mrna Splicing ◽

Founder Mutations ◽

Promising Treatment ◽

Lead Candidate ◽

Dose Dependent

AbstractMutations in USH2A, encoding usherin, are the most common cause of syndromic and non-syndromic retinitis pigmentosa (RP). The two founder mutations in exon 13 (c.2299delG and c.2276G>T) collectively account for ~34% of USH2A-associated RP cases. Skipping of exon 13 from the USH2A transcript during pre-mRNA splicing presents a potential treatment modality in which the resulting transcript is predicted to encode a slightly shortened usherin protein. Morpholino-induced skipping of ush2a exon 13 in larvae of the previously published ush2a exon 13 zebrafish mutant resulted in the production of usherinΔexon13 and completely restored retinal function. RNA antisense oligonucleotides were investigated for their potential to specifically induce human USH2A exon 13 skipping. Lead candidate QR-421a induced dose-dependent exon 13 skipping in iPSC-derived photoreceptor precursors from a patient homozygous for the USH2A c.2299delG mutation. Intravitreal delivery of QR-421a in non-human primates showed that QR-421a penetrates the retinal outer nuclear layer and induces detectable levels of exon 13 skipping until at least 3 months post injection. In conclusion, QR-421a-induced exon skipping proves to be a highly promising treatment for RP caused by mutations in exon 13 of the USH2A gene.

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Intramuscular Evaluation of Chimeric Locked Nucleic Acid/2’OMethyl-Modified Antisense Oligonucleotides for Targeted Exon 23 Skipping in Mdx Mice

Pharmaceuticals ◽

10.3390/ph14111113 ◽

2021 ◽

Vol 14 (11) ◽

pp. 1113

Author(s):

Michaella Georgiadou ◽

Melina Christou ◽

Kleitos Sokratous Sokratous ◽

Jesper Wengel ◽

Kyriaki Michailidou ◽

...

Keyword(s):

Nucleic Acid ◽

Therapeutic Potential ◽

Exon Skipping ◽

Dystrophin Gene ◽

Locked Nucleic Acid ◽

Mdx Mice ◽

Muscle Fibres ◽

Systemic Delivery ◽

Reading Frame ◽

Dystrophin Protein

Duchenne muscular dystrophy (DMD) is a fatal disorder characterised by progressive muscle wasting. It is caused by mutations in the dystrophin gene, which disrupt the open reading frame leading to the loss of functional dystrophin protein in muscle fibres. Antisense oligonucleotide (AON)-mediated skipping of the mutated exon, which allows production of a truncated but partially functional dystrophin protein, has been at the forefront of DMD therapeutic research for over two decades. Nonetheless, novel nucleic acid modifications and AON designs are continuously being developed to improve the clinical benefit profile of current drugs in the DMD pipeline. We herein designed a series of 15mer and 20mer AONs, consisting of 2’O-Methyl (2’OMe)- and locked nucleic acid (LNA)-modified nucleotides in different percentage compositions, and assessed their efficiency in inducing exon 23 skipping and dystrophin restoration in locally injected muscles of mdx mice. We demonstrate that LNA/2’OMe AONs with a 30% LNA composition were significantly more potent in inducing exon skipping and dystrophin restoration in treated mdx muscles, compared to a previously tested 2’OMe AON and LNA/2’OMe chimeras with lower or higher LNA compositions. These results underscore the therapeutic potential of LNA/2’OMe AONs, paving the way for further experimentation to evaluate their benefit-toxicity profile following systemic delivery.

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Basal exon skipping and nonsense-associated altered splicing allows bypassing complete CEP290 loss-of-function in individuals with unusually mild retinal disease

Human Molecular Genetics ◽

10.1093/hmg/ddy179 ◽

2018 ◽

Vol 27 (15) ◽

pp. 2689-2702 ◽

Cited By ~ 11

Author(s):

Iris Barny ◽

Isabelle Perrault ◽

Christel Michel ◽

Mickael Soussan ◽

Nicolas Goudin ◽

...

Keyword(s):

Exon Skipping ◽

Retinal Disease ◽

Loss Of Function

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Subcellular localization of mutant P23H rhodopsin in an RFP fusion knockin mouse model of retinitis pigmentosa

10.1101/2021.10.11.463949 ◽

2021 ◽

Author(s):

Michael A Robichaux ◽

Vy Nguyen ◽

Fung Chan ◽

Lavanya Kailasam ◽

John H Wilson ◽

...

Keyword(s):

Cell Death ◽

Mouse Model ◽

Retinitis Pigmentosa ◽

Outer Nuclear Layer ◽

Retinal Disease ◽

Tunel Staining ◽

Protein Accumulation ◽

Mrna Levels ◽

Rod Photoreceptor ◽

Photoreceptor Neurons

The P23H mutation in rhodopsin (Rho), the visual pigment protein in rod photoreceptor neurons, is the most common genetic cause of autosomal dominant retinitis pigmentosa (adRP), a retinal disease that causes blindness. Despite multiple studies in animal models, the subcellular details of the fate of misfolded mutant Rho in rod photoreceptors have not been completely defined. We generated a new mouse model of adRP, in which the P23H-Rho mutant allele is fused to Tag-RFP-T (P23HhRhoRFP). In heterozygotes, outer segments formed, and WT rhodopsin was properly localized there, but mutant P23H-Rho protein was specifically mislocalized in the inner segments of rods. Despite this cellular phenotype, the P23HhRhoRFP heterozygous mice exhibited only slowly progressing retinal degeneration; in ERG recordings, scotopic a-wave amplitudes were reduced by 24% and 26% at 30 days and 90 days respectively, and the corresponding scotopic b-waves by 18% and 24%. Outer nuclear layer thickness was still 80% of WT at 90 days, but at 364 days had declined to 40% of WT. Transmission electron microscopy revealed greatly expanded membrane lamellae in the inner segment, and by fluorescence imaging, we determined that the mislocalized P23HhRhoRFP was contained in greatly expanded endoplasmic reticulum (ER) membranes. TUNEL staining revealed a slow pace of cell death involving chromosomal endonucleolytic degradation. Quantification of mRNA for markers of ER stress and the unfolded protein response revealed little or no increases in levels of messages encoding the proteins BiP, CHOP, ATF6, XBP1, PERK, Eif2α and Derlin-1, but a decreased level of total Rhodopsin (mouse + human) mRNA levels. The decline in the rate of cell death after an initial burst suggests that P23HhRhoRFP mutant rods undergo an adaptative process that prolongs survival despite gross P23HhRhoRFP protein accumulation in the ER. Because of its slowly progressing nature, and easy visualization of the mutant protein, the P23H-Rho-RFP mouse may represent a useful tool for the future study of the pathology and treatment of P23H-Rho and adRP.

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Retinitis pigmentosa is associated with shifts in the gut microbiome

Scientific Reports ◽

10.1038/s41598-021-86052-1 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Oksana Kutsyr ◽

Lucía Maestre-Carballa ◽

Mónica Lluesma-Gomez ◽

Manuel Martinez-Garcia ◽

Nicolás Cuenca ◽

...

Keyword(s):

Retinitis Pigmentosa ◽

Gut Microbiome ◽

Functional Decline ◽

Retinal Disease ◽

Photoreceptor Cells ◽

Amplicon Sequencing ◽

Rrna Gene ◽

Sequencing Data ◽

Alpha And Beta Diversity ◽

Potential Biomarker

AbstractThe gut microbiome is known to influence the pathogenesis and progression of neurodegenerative diseases. However, there has been relatively little focus upon the implications of the gut microbiome in retinal diseases such as retinitis pigmentosa (RP). Here, we investigated changes in gut microbiome composition linked to RP, by assessing both retinal degeneration and gut microbiome in the rd10 mouse model of RP as compared to control C57BL/6J mice. In rd10 mice, retinal responsiveness to flashlight stimuli and visual acuity were deteriorated with respect to observed in age-matched control mice. This functional decline in dystrophic animals was accompanied by photoreceptor loss, morphologic anomalies in photoreceptor cells and retinal reactive gliosis. Furthermore, 16S rRNA gene amplicon sequencing data showed a microbial gut dysbiosis with differences in alpha and beta diversity at the genera, species and amplicon sequence variants (ASV) levels between dystrophic and control mice. Remarkably, four fairly common ASV in healthy gut microbiome belonging to Rikenella spp., Muribaculaceace spp., Prevotellaceae UCG-001 spp., and Bacilli spp. were absent in the gut microbiome of retinal disease mice, while Bacteroides caecimuris was significantly enriched in mice with RP. The results indicate that retinal degenerative changes in RP are linked to relevant gut microbiome changes. The findings suggest that microbiome shifting could be considered as potential biomarker and therapeutic target for retinal degenerative diseases.

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