Dataset Information

A new mouse model for retinal degeneration due to Fam161a deficiency.

ABSTRACT: FAM161A mutations are the most common cause of inherited retinal degenerations in Israel. We generated a knockout (KO) mouse model, Fam161a^tm1b/tm1b, lacking the major exon #3 which was replaced by a construct that include LacZ under the expression of the Fam161a promoter. LacZ staining was evident in ganglion cells, inner and outer nuclear layers and inner and outer-segments of photoreceptors in KO mice. No immunofluorescence staining of Fam161a was evident in the KO retina. Visual acuity and electroretinographic (ERG) responses showed a gradual decrease between the ages of 1 and 8 months. Optical coherence tomography (OCT) showed thinning of the whole retina. Hypoautofluorescence and hyperautofluorescence pigments was observed in retinas of older mice. Histological analysis revealed a progressive degeneration of photoreceptors along time and high-resolution transmission electron microscopy (TEM) analysis showed that photoreceptor outer segment disks were disorganized in a perpendicular orientation and outer segment base was wider and shorter than in WT mice. Molecular degenerative markers, such as microglia and CALPAIN-2, appear already in a 1-month old KO retina. These results indicate that a homozygous Fam161a frameshift mutation affects retinal function and causes retinal degeneration. This model will be used for gene therapy treatment in the future.

SUBMITTER: Beryozkin A

PROVIDER: S-EPMC7820261 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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A new mouse model for retinal degeneration due to Fam161a deficiency.

Beryozkin Avigail A Matsevich Chen C Obolensky Alexey A Kostic Corinne C Arsenijevic Yvan Y Wolfrum Uwe U Banin Eyal E Sharon Dror D

Scientific reports 20210121 1

FAM161A mutations are the most common cause of inherited retinal degenerations in Israel. We generated a knockout (KO) mouse model, Fam161a<sup>tm1b/tm1b</sup>, lacking the major exon #3 which was replaced by a construct that include LacZ under the expression of the Fam161a promoter. LacZ staining was evident in ganglion cells, inner and outer nuclear layers and inner and outer-segments of photoreceptors in KO mice. No immunofluorescence staining of Fam161a was evident in the KO retina. Visual a ...[more]

PMID: 33479377

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Project description:Retinitis Pigmentosa (RP) is a group of inherited retinal diseases characterized by progressive loss of rod followed by cone photoreceptors. An especially early onset form of RP with blindness in teenage years is caused by mutations in mertk, the gene encoding the clearance phagocytosis receptor Mer tyrosine kinase (MerTK). The cause for blindness in mutant MerTK-associated RP (mutMerTK-RP) is the failure of retinal pigment epithelial cells in diurnal phagocytosis of spent photoreceptor outer segment debris. However, the early onset and very fast progression of degeneration in mutMerTK-RP remains unexplained. Here, we explored the role of microglia in the Royal College of Surgeons (RCS) rat model of mutMerTK-RP. We found elevated levels of inflammatory cytokines and CD68 microglia activation marker, and more ionized calcium-binding adapter molecule 1 (Iba-1) positive microglia in RCS retina when compared to wild-type retina as early as postnatal day 14 (P14). Strikingly, renewal of photoreceptor outer segments in P14 wild-type rat retina is still immature with low levels of RPE phagocytosis implying that at this early age lack of this process in RCS rats is unlikely to distress photoreceptors. Although the total number of Iba-1 positive retinal microglia remains constant from P14 to P30, we observed increasing numbers of microglia in the outer retina from P20 implying migration to the outer retina before onset of photoreceptor cell death at ~P25. Iba-1 and CD68 levels also increase in the retina during this time period suggesting microglia activation. To determine whether microglia affect the degenerative process, we suppressed retinal microglia in vivo using tamoxifen or a combination of tamoxifen and liposomal clodronate. Treatments partly prevented elevation of Iba-1 and CD68 and relocalization of microglia. Moreover, treatments led to partial but significant retention of photoreceptor viability and photoreceptor function. We conclude that loss of the phagocytosis receptor MerTK causes microglia activation and relocalization in the retina before lack of RPE phagocytosis causes overt retinal degeneration, and that microglia activities accelerate loss of photoreceptors in mutMerTK-RP. These results suggest that therapies targeting microglia may delay onset and slow the progression of this blinding disease.

Project description:PurposePathogenic variants in FAM161A are the most common cause of retinitis pigmentosa in Israel. Two founder pathogenic variants explain the vast majority of cases of Jewish origin, 1 being a nonsense variant (p.Arg523∗). The aim of this study was to generate a knock-in (KI) mouse model harboring the corresponding p.Arg512∗ pathogenic variant and characterize the course of retinal disease.DesignExperimental study of a mouse animal model.Subjects/participants/controlsA total of 106 Fam161a knock-in mice and 29 wild-type mice with C57BL/6J background particiapted in this study.MethodsHomozygous Fam161a p.Arg512∗ KI mice were generated by Cyagen Biosciences. Visual acuity (VA) was evaluated using optomotor tracking response and retinal function was assessed by electroretinography (ERG). Retinal structure was examined in vivo using OCT and fundus autofluorescence imaging. Retinal morphometry was evaluated by histologic and immunohistochemical (IHC) analyses.Main outcome measuresVisual and retinal function assessments, clinical imaging examinations, quantitative histology, and IHC studies of KI as compared with wild-type (WT) mice retinas.ResultsThe KI model was generated by replacing 3 bp, resulting in p.Arg512∗. Homozygous KI mice that had progressive loss of VA and ERG responses until the age of 18 months, with no detectable response at 21 months. OCT showed complete loss of the outer nuclear layer at 21 months. Fundus autofluorescence imaging revealed progressive narrowing of blood vessels and formation of patchy hyper-autofluorescent and hypo-autofluorescent spots. Histologic analysis showed progressive loss of photoreceptor nuclei. Immunohistochemistry staining showed Fam161a expression mainly in photoreceptors cilia and the outer plexiform layer (OPL) in WT mice retinas, whereas faint expression was evident mainly in the cilia and OPL of KI mice.ConclusionsThe Fam161a - p.Arg512∗ KI mouse model is characterized by widespread retinal degeneration with relatively slow progression. Surprisingly, disease onset is delayed and progression is slower compared with the previously reported knock-out model. The common human null mutation in the KI mouse model is potentially amenable for correction by translational read-through-inducing drugs and by gene augmentation therapy and RNA editing, and can serve to test these treatments as a first step toward possible application in patients.Financial disclosuresThe author(s) have no proprietary or commercial interest in any materials discussed in this article.

Dataset Information

A new mouse model for retinal degeneration due to Fam161a deficiency.

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A new mouse model for retinal degeneration due to Fam161a deficiency.

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