Loss of Otx2 in the adult retina disrupts retinal pigment epithelium function, causing photoreceptor degeneration.

Photoreceptors are specialized neurons of the retina that receive nursing from the adjacent retinal pigment epithelium (RPE). Frequent in the elderly, photoreceptor loss can originate from primary dysfunction of either cell type. Despite intense interest in the etiology of these diseases, early molecular actors of late-onset photoreceptor degeneration remain elusive, mostly because of the lack of dedicated models. Conditional Otx2 ablation in the adult mouse retina elicits photoreceptor degeneration, providing a new model of late-onset neuronal disease. Here, we use this model to identify the earliest events after Otx2 ablation. Electroretinography and gene expression analyses suggest a nonautonomous, RPE-dependent origin for photoreceptor degeneration. This is confirmed by RPE-specific ablation of Otx2, which results in similar photoreceptor degeneration. In contrast, constitutive Otx2 expression in RPE cells prevents degeneration of photoreceptors in Otx2-ablated retinas. We use chromatin immunoprecipitation followed by massive sequencing (ChIP-seq) analysis to identify the molecular network controlled in vivo by Otx2 in RPE cells. We uncover four RPE-specific functions coordinated by Otx2 that underpin the cognate photoreceptor degeneration. Many direct Otx2 target genes are associated with human retinopathies, emphasizing the significance of the model. Importantly, we report a secondary genetic response after Otx2 ablation, which largely precedes apoptosis of photoreceptors, involving inflammation and stress genes. These findings thus provide novel general markers for clinical detection and prevention of neuronal cell death.

The homeobox gene Otx2 in development and disease.

The Otx2 gene encodes a transcription factor essential for the normal development of brain, cerebellum, pineal gland, and eye. In the retina, Otx2 has essential functions from early embryogenesis to adulthood. As soon as the optic vesicle is formed, the gene is required for retinal pigment epithelium specification. Otx2 is also a key regulator of photoreceptor genesis and differentiation, and is required after birth for bipolar cells terminal maturation. Otx2 expression is maintained in the differentiated retina wherein the gene is critical for the outer retina maintenance. In the visual cortex, the gene modulates the neuronal plasticity through a paracrine mechanism. OTX2 heterozygous mutations in humans have been linked to severe ocular malformations associated with brain abnormalities and pituitary dysfunction. Recent studies have also established the OTX2 gene as an oncogene for medulloblastoma, a malignant brain tumour originating in the cerebellum.

A new GFP-tagged line reveals unexpected Otx2 protein localization in retinal photoreceptors.

BACKGROUND: Dynamic monitoring of protein expression and localization is fundamental to the understanding of biological processes. The paired-class homeodomain-containing transcription factor Otx2 is essential for normal head and brain development in vertebrates. Recent conditional knockout studies have pointed to multiple roles of this protein during late development and post-natal life. Yet, later expression and functions remain poorly characterized as specific reagents to detect the protein at any stage of development are still missing. RESULTS: We generated a new mouse line harbouring an insertion of the GFP gene within the Otx2 coding sequence to monitor the gene activity while preserving most of its functions. Our results demonstrate that this line represents a convenient tool to capture the dynamics of Otx2 gene expression from early embryonic stages to adulthood. In addition, we could visualize the intracellular location of Otx2 protein. In the retina, we reinterpret the former view of protein distribution and show a further level of regulation of intranuclear protein localization, which depends on the cell type. CONCLUSION: The GFP-tagged Otx2 mouse line fully recapitulates previously known expression patterns and brings additional accuracy and easiness of detection of Otx2 gene activity. This opens up the way to live imaging of a highly dynamic actor of brain development and can be adapted to any mutant background to probe for genetic interaction between Otx2 and the mutated gene.

Nonpenetrating external trabeculectomy for congenital glaucoma: a retrospective study.

OBJECTIVE: To evaluate the results of nonpenetrating external trabeculectomy (NPET) for primary congenital glaucoma (CG). DESIGN: Retrospective, noncomparative, interventional case series. PARTICIPANTS: Forty-three eyes of 27 consecutive patients with primary CG. METHODS: Initial intent of NPET with intraoperative conversion to trabeculectomy in cases where aqueous humor outflow was deemed insufficient or where Schlemm's canal appeared to be absent. MAIN OUTCOME MEASURES: Intraocular pressure (IOP). Success was defined as an IOP less than 12.5 mmHg at 1 year after the procedure or later, using adjunctive pressure-lowering topical medications whenever needed. RESULTS: Mean initial measures of IOP were 18.8 mmHg. Of the 43 eyes, a total of 13 required conversion to trabeculectomy: 9 because of insufficient filtration, 3 because of an apparent absence of Schlemm's canal, and 1 because of accidental perforation. Of these 13 eyes that ultimately underwent trabeculectomy, 11 achieved successful IOP control, 3 in association with topical therapy. In 1 eye, a retinal detachment developed, and in 7 eyes, other complications were observed. Among the 30 remaining eyes that underwent NPET, 2 underwent the procedure twice, and 1 eye underwent the procedure 3 times. Postoperative complications were not noted in this NPET-only group. Mean postoperative IOP was 10.8 mmHg, with final IOP controlled in 28 of the 30 eyes (93%; P<0.0001), occasionally after repeat surgeries and in combination with topical therapy. CONCLUSIONS: Nonpenetrating external trabeculectomy may be considered as an initial procedure for some cases of primary CG. It appears to be an alternative to trabeculectomy with fewer risks of postoperative complications.

New phenotype associated with an Arg116Cys mutation in the CRYAA gene: nuclear cataract, iris coloboma, and microphthalmia.

OBJECTIVE: To describe a new phenotype with an arginine-to-cysteine mutation at position 116 (Arg116Cys) in the CRYAA gene. METHODS: We investigated a 4-generation French family with autosomal dominant cataract and performed a genetic linkage analysis using microsatellite DNA markers encompassing 15 known cataract loci. Exons 1, 2, and 3 and flanking intronic sequences of the CRYAA gene were amplified and analyzed using direct sequencing. RESULTS: All of the affected individuals had nuclear cataract and iris coloboma. Genetic analysis revealed the previously described Arg116Cys mutation in the CRYAA gene in the heterozygous state in all of the affected members of the family but not in unaffected individuals. CONCLUSION: To our knowledge, this is the first case to date in which an Arg116Cys mutation in the CRYAA gene was associated with nuclear cataract and iris coloboma. CLINICAL RELEVANCE: This study indicates that an Arg116Cys mutation in the CRYAA gene could be associated with an unusual phenotype in affected individuals. In this family, the clinical observation of iris coloboma allows for the possibility of identifying individuals carrying the mutation. Iris coloboma is particularly important in terms of perinatal diagnosis because its detection in the newborn requires a careful and regular examination of the lens.

Ocular anomalies associated with interstitial deletion of chromosome 2q31: case report and review.

We describe a newborn girl with multiple malformations associated with an interstitial deletion of chromosome 2q (q24q32). Clinical findings included growth retardation, microcephaly, facial malformations, common atrioventricular canal, digital anomalies of both hands and feet, and ovarian hypoplasia. Bilateral ocular anomalies included down-slanting palpebral fissures, blepharophimosis, microphthalmia, uveal coloboma, and corneal opacity. Chromosomal segment 2q31 may play a major role in the development of the eye and its adnexa.

Systemic abnormalities in children with congenital optic disc excavations.

PURPOSE: Together with optic disc hypoplasia, excavated optic disc anomalies represent the most frequent congenital abnormality involving the optic nerve head. The purpose of the present study was to retrospectively review the results of a screening for extraocular abnormalities in children presenting with congenital optic disc excavations. MATERIALS AND METHODS: The medical records of 37 patients diagnosed with a unilateral or bilateral non glaucomatous optic disc excavation were retrospectively reviewed to analyze the result of the extra ocular evaluation and to report the associated ocular abnormalities. RESULTS: An ocular abnormality was observed in conjunction with the excavated optic disc in 31% of the eyes. The systematic investigations revealed the presence of at least one extra-ocular disorder in 48% of the cases, and the optic disc excavation could be considered as syndromic in 30% of patients. The prevalence of extraocular malformations was significantly higher in infants presenting with associated ocular malformations or abnormal vision/development. CONCLUSIONS: The present study suggests that a systematic approach to search for any associated systemic abnormalities could be envisioned in patients presenting with congenital excavated optic discs, and particularly those presenting with abnormal vision, associated ocular defects or abnormal development.

Chromosome 6p25 deletion syndrome: report of a case with optic disc coloboma and review of published ophthalmic findings.

PURPOSE: The 6p25 deletion syndrome is a rare disorder characterized by Dandy-Walker malformation, congenital heart defects, developmental delay, dysmorphic facial features, and malformations of the anterior segment of the eye with a risk for glaucoma. Here we report a child harboring a cryptic de novo 6p25 deletion, bilateral optic disc coloboma and characteristic anterior segment anomalies. We review reported ophthalmic findings in patients with this syndrome. MATERIALS AND METHODS: Retrospective case review of a 4-day-old male with Dandy-Walker malformation and cardiac defects who was referred with a suspected diagnosis of iris coloboma. RESULTS: The ophthalmic examination showed bilateral corectopia associated with posterior embryotoxon. Fundus examination revealed bilateral optic disc excavation, which was diagnosed as colobomatous because of its configuration and stability over time. Because of the association of posterior embryotoxon with Dandy-Walker malformation, a terminal 6p deletion syndrome was clinically suspected. Array comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH) studies revealed a 3.2 Mb deletion at 6p25.2p25.3 including the FOXC1 gene. Neither unaffected parent carried this deletion. CONCLUSIONS: Optic disc colobomas may be found in patients carrying a 6p25 deletion. This has the potential to confound assessment of affected children for glaucoma and intracranial hypertension.

Otx2 gene deletion in adult mouse retina induces rapid RPE dystrophy and slow photoreceptor degeneration.

BACKGROUND: Many developmental genes are still active in specific tissues after development is completed. This is the case for the homeobox gene Otx2, an essential actor of forebrain and head development. In adult mouse, Otx2 is strongly expressed in the retina. Mutations of this gene in humans have been linked to severe ocular malformation and retinal diseases. It is, therefore, important to explore its post-developmental functions. In the mature retina, Otx2 is expressed in three cell types: bipolar and photoreceptor cells that belong to the neural retina and retinal pigment epithelium (RPE), a neighbour structure that forms a tightly interdependent functional unit together with photoreceptor cells. METHODOLOGY/PRINCIPAL FINDINGS: Conditional self-knockout was used to address the late functions of Otx2 gene in adult mice. This strategy is based on the combination of a knock-in CreERT2 allele and a floxed allele at the Otx2 locus. Time-controlled injection of tamoxifen activates the recombinase only in Otx2 expressing cells, resulting in selective ablation of the gene in its entire domain of expression. In the adult retina, loss of Otx2 protein causes slow degeneration of photoreceptor cells. By contrast, dramatic changes of RPE activity rapidly occur, which may represent a primary cause of photoreceptor disease. CONCLUSIONS: Our novel mouse model uncovers new Otx2 functions in adult retina. We show that this transcription factor is necessary for long-term maintenance of photoreceptors, likely through the control of specific activities of the RPE.

Anterior segment dysgenesis in a child with factor VII deficiency.

PURPOSE: To describe the first case of anterior segment dysgenesis associated with factor VII congenital deficit (hypoproconvertinemia). METHOD: A 2-month-old child with factor VII deficiency was referred to our clinic because of corneal opacities. The child was born to consanguineous parents and severe factor VII deficiency was diagnosed on the third day of life because of gastrointestinal bleeding. RESULT: Ocular examination under anesthesia showed bilateral corneal opacities with adherent iris strands and peripheral anterior synechiae. The intra-ocular pressure was normal in both eyes and there were neither signs of cataracts nor glaucomatous optic nerve damage. CONCLUSION: This observation provide new information on the possible ocular findings in patients with hypoproconvertinemia. Based on this report, we suggest that careful coagulation screening should be considered in children who possess idiopathic anterior segment dysgenesis aiming at identifying the possible coagulation disorder.

Combined pars plana phacofragmentation, vitrectomy, and Artisan lens implantation for traumatic subluxated cataracts.

PURPOSE: To report on the outcome of combined pars plana phacofragmentation, vitrectomy, and Artisan lens implantation in the management of subluxated cataracts. METHODS: This prospective, interventional, nonrandomized case series included nine eyes of seven consecutive adult patients with traumatic lens subluxation. Pre- and postoperative data (complete manifest refraction, best spectacle-corrected visual acuity, slit-lamp examination findings, intraocular pressure, fundus status, numerical density of endothelial cells, corneal thickness, and complications) were collected prospectively for all patients. RESULTS: After a median postoperative follow-up of 12 months (range, 8-18 months), a mean spherical equivalent of -0.50 +/- 0.87 diopter (range, +1 to -1.50 diopter) was achieved. The mean logarithm of the minimum angle of resolution visual acuity improved from 1 (preoperatively) to 0.1 (postoperatively) (P = 0.007, Wilcoxon test). Median endothelial cell losses of 15 +/- 8% (P = 0.008) and 14 +/- 16% (P = 0.011) were registered at follow-ups of 1 month and 12 months, respectively. Postoperative complications included chronic intraocular inflammation and superior corectopia. CONCLUSIONS: Our procedure appears to be a safe, accurate, stable, and efficacious option for the management of traumatic subluxated cataracts in adults. However, longer-term data are needed to evaluate the corneal endothelium.