New Insights Into Pentosan Polysulfate Maculopathy.

BACKGROUND AND OBJECTIVE: To provide new insights into toxic maculopathy secondary to pentosan polysulfate (PPS) utilizing multimodal testing. PATIENTS AND METHODS: Retrospective case-series of four patients from two academic centers evaluated with multimodal imaging, electrophysiology, dark adaptometry (DA), and genetic testing. RESULTS: Median age was 58 years, exposure to PPS was 18.5 years, and cumulative dose of was 2,025 grams. Seven of eight eyes had visual acuity of 20/40 or better. Optical coherence tomography (OCT) angiography demonstrated increased choriocapillaris flow voids (54.25%) in cases compared to controls (13.2%). Two subjects had abnormal foveal avascular zone configurations. Two subjects demonstrated collapse of the retinal pigment epithelium nodular excrescences and progressive retinal thinning over 4 to 5 years on OCT. Electrophysiology was normal (3/3 patients), but DA was delayed (2/2 patients). CONCLUSIONS: The authors describe novel findings of PPS maculopathy, including flow voids in the choriocapillaris. Progressive retinal thinning may suggest a secondary retinal effect. These findings may improve understanding of the pathophysiology. [Ophthalmic Surg Lasers Imaging Retina. 2021;52:13-22.].

Adjunctive re-dilation for early cicatrization after punctoplasty.

PURPOSE: To evaluate punctoplasty outcomes with adjunctive in-office probing of early post-procedure cicatricial changes. METHOD: Retrospective analysis of all eyes undergoing 3-snip punctoplasty by a single surgeon between August 1,2008 and June 30, 2011. RESULTS: Twenty-two patients were eligible for this study. Twenty-eight eyes (15 right, 13 left) underwent punctoplasty. Twenty-three eyes underwent in-office post-procedure dilation for early cicatricial changes. Anatomical success was achieved in 22 patients (100%). Twenty-one patients (95.5%) reported improvement in epiphora. CONCLUSIONS: Functional and anatomical success rates after punctoplasty may be improved by close post-procedure follow-up with in-office re-dilation for recurrent punctal cicatrization.

FMRP stalls ribosomal translocation on mRNAs linked to synaptic function and autism.

FMRP loss of function causes Fragile X syndrome (FXS) and autistic features. FMRP is a polyribosome-associated neuronal RNA-binding protein, suggesting that it plays a key role in regulating neuronal translation, but there has been little consensus regarding either its RNA targets or mechanism of action. Here, we use high-throughput sequencing of RNAs isolated by crosslinking immunoprecipitation (HITS-CLIP) to identify FMRP interactions with mouse brain polyribosomal mRNAs. FMRP interacts with the coding region of transcripts encoding pre- and postsynaptic proteins and transcripts implicated in autism spectrum disorders (ASD). We developed a brain polyribosome-programmed translation system, revealing that FMRP reversibly stalls ribosomes specifically on its target mRNAs. Our results suggest that loss of a translational brake on the synthesis of a subset of synaptic proteins contributes to FXS. In addition, they provide insight into the molecular basis of the cognitive and allied defects in FXS and ASD and suggest multiple targets for clinical intervention.

Discrimination of common and unique RNA-binding activities among Fragile X mental retardation protein paralogs.

Fragile X mental retardation is caused by loss-of-function of a single gene encoding FMRP, an RNA-binding protein that harbors three canonical RNA-binding domains, two KH-type and one RGG box. Two autosomal paralogs of FMRP, FXR1P and FXR2P, are similar to FMRP in their overall structure, including the presence of putative RNA-binding domains, but to what extent they provide functional redundancy with FMRP is unclear. Although FMRP has been characterized as a polyribosome-associated regulator of translation, less is known about the functions of FXR1P and FXR2P. For example, FMRP binds intramolecular G-quadruplex and kissing complex RNA (kcRNA) ligands via the RGG box and KH2 domain, respectively, although the RNA ligands of FXR1P and FXR2P are unknown. Here we demonstrate that FXR1P and FXR2P KH2 domains bind kcRNA ligands with the same affinity as the FMRP KH2 domain although other KH domains do not. RNA ligand recognition by this family is highly conserved, as the KH2 domain of the single Drosophila ortholog, dFMRP, also binds kcRNA. kcRNA was able to displace FXR1P and FXR2P from polyribosomes as it does for FMRP, and this displacement was FMRP-independent. This suggests that all three family members recognize the same binding site on RNA mediating their polyribosome association, and that they may be functionally redundant with regard to this aspect of translational control. In contrast, FMRP is unique in its ability to recognize G-quadruplexes, suggesting the FMRP RGG domain may play a non-redundant role in the pathophysiology of the disease.

Kissing complex RNAs mediate interaction between the Fragile-X mental retardation protein KH2 domain and brain polyribosomes.

Fragile-X mental retardation is caused by loss of function of a single gene encoding the Fragile-X mental retardation protein, FMRP, an RNA-binding protein that harbors two KH-type and one RGG-type RNA-binding domains. Previous studies identified intramolecular G-quartet RNAs as high-affinity targets for the RGG box, but the relationship of RNA binding to FMRP function and mental retardation remains unclear. One severely affected patient harbors a missense mutation (I304N) within the second KH domain (KH2), and some evidence suggests this domain may be involved in the proposed role of FMRP in translational regulation. We now identify the RNA target for the KH2 domain as a sequence-specific element within a complex tertiary structure termed the FMRP kissing complex. We demonstrate that the association of FMRP with brain polyribosomes is abrogated by competition with the FMRP kissing complex RNA, but not by high-affinity G-quartet RNAs. We conclude that mental retardation associated with the I304N mutation, and likely the Fragile-X syndrome more generally, may relate to a crucial role for RNAs harboring the kissing complex motif as targets for FMRP translational regulation.

Fragile X mental retardation protein is associated with translating polyribosomes in neuronal cells.

Fragile X mental retardation protein (FMRP) is an RNA binding protein encoded by the gene FMR1, whose expression is impaired in patients with fragile X mental retardation. The association of FMRP with polyribosomes in non-neural cell lines has previously suggested that FMRP is involved in translational regulation. However, the relevance of these studies to neuronal function has been questioned by the finding that FMRP in brain is not associated with polyribosomes, but is part of small ribonucleo-protein complexes that do not appear to include ribosomes. Here we optimize methods to analyze brain polyribosomes, allowing us to definitively demonstrate that FMRP forms complexes with cortical brain polyribosomes. Moreover, we demonstrate in neuroblastoma cells that the FMRP-polyribosome complexes are sensitive to puromycin, a drug that targets actively translating ribosomes. These data indicate that FMRP associates with functional polyribosomes in neurons.