Random Allelic Expression in Inherited Retinal Disease Genes.

Inherited retinal diseases (IRDs) are a significant contributor to visual loss in children and young adults, falling second only to diabetic retinopathy. Understanding the pathogenic mechanisms of IRDs remains paramount. Some autosomal genes exhibit random allelic expression (RAE), similar to X-chromosome inactivation. This study identifies RAE genes in IRDs. Genes in the Retinal Information Network were cross-referenced with the recent literature to identify expression profiles, RAE, or biallelic expression (BAE). Loss-of-function intolerance (LOFI) was determined by cross-referencing the existing literature. Molecular and biological pathways that are significantly enriched were evaluated using gene ontology. A total of 184 IRD-causing genes were evaluated. Of these, 31 (16.8%) genes exhibited RAE. LOFI was exhibited in 6/31 (19.4%) of the RAE genes and 18/153 (11.8%) of the BAE genes. Brain tissue exhibited BAE in 107/128 (83.6%) genes for both sexes. The molecular pathways significantly enriched among BAE genes were photoreceptor activity, tubulin binding, and nucleotide/ribonucleotide binding. The biologic pathways significantly enriched for RAE genes were equilibrioception, parallel actin filament bundle assembly, photoreceptor cell outer segment organization, and protein depalmitoylation. Allele-specific expression may be a mechanism underlying IRD phenotypic variability, with clonal populations of embryologic precursor cells exhibiting RAE. Brain tissue preferentially exhibited BAE, possibly due to selective pressures against RAE. Pathways critical for cellular and visual function were enriched in BAE, which may offer a survival benefit.

Phosphomimetics at Ser199/Ser202/Thr205 in Tau Impairs Axonal Transport in Rat Hippocampal Neurons.

Our understanding of the biological functions of the tau protein now includes its role as a scaffolding protein involved in signaling regulation, which also has implications for tau-mediated dysfunction and degeneration in Alzheimer's disease and other tauopathies. Recently, we found that pseudophosphorylation at sites linked to the pathology-associated AT8 phosphoepitope of tau disrupts normal fast axonal transport through a protein phosphatase 1 (PP1)-dependent pathway in squid axoplasm. Activation of the pathway and the resulting transport deficits required tau's N-terminal phosphatase-activating domain (PAD) and PP1 but the connection between tau and PP1 was not well defined. Here, we studied functional interactions between tau and PP1 isoforms and their effects on axonal transport in mammalian neurons. First, we found that wild-type tau interacted with PP1α and PP1γ primarily through its microtubule-binding repeat domain. Pseudophosphorylation of tau at S199/S202/T205 (psTau) increased PAD exposure, enhanced interactions with PP1γ, and increased active PP1γ levels in mammalian cells. Expression of psTau also significantly impaired axonal transport in primary rat hippocampal neurons. Deletion of PAD in psTau significantly reduced the interaction with PP1γ, eliminated increases of active PP1γ levels, and rescued axonal transport impairment in neurons. These data suggest that a functional consequence of phosphorylation within S199-T205 in tau, which occurs in AD and several other tauopathies, may be aberrant interaction with and activation of PP1γ and subsequent axonal transport disruption in a PAD-dependent fashion.

Intraoperative Complication Rates in Cataract Surgery After Resuming Surgery Following the COVID-19 Shutdown.

Purpose: To evaluate surgeon performance and intraoperative complication rates of cataract surgery after resumption of elective surgeries following the operating room (OR) shutdown from the coronavirus disease 2019 (COVID-19) pandemic. Subjective surgical experience is also evaluated. Methods: This is a retrospective comparative study which analyzes cataract surgeries performed at an inner city, tertiary academic center. Cataract surgeries were categorized into Pre-Shutdown (January 1-March 18, 2020), and Post-Shutdown, for all cases which occurred after surgeries resumed (May 11-July 31, 2020). No cases were performed between March 19 and May 10, 2020. Patients undergoing combined cataract and minimally invasive glaucoma surgery (MIGS) were included, but MIGS complications were not counted as cataract complications. No other combined cataract-other ophthalmic surgeries were included. A survey was used to gather subjective surgeon experience. Results: A total of 480 cases (n=306 Pre-Shutdown and n=174 Post-Shutdown) were analyzed. Although there was a higher frequency of complex cataract surgeries performed Post-Shutdown (5.2% vs 21.3%; p<0.00001), complication rates before versus after the shutdown were not statistically significant (9.2% vs 10.3%; p=0.75). Phacoemulsification was the step of cataract surgery in which residents were most concerned about when returning to the OR. Conclusion: After the surgical hiatus due to COVID-19, significantly more complex cataract surgeries were reported and surgeons reported higher general anxiety level when first returning to the OR. Increased anxiety did not lead to higher surgical complications. This study provides a framework to understand surgical expectations and outcomes for patients whose surgeons faced a prolonged two-month hiatus from cataract surgery.

The Vision Detroit Project: Integrated Screening and Community Eye-Health Education Interventions Improve Eyecare Awareness.

PURPOSE: Poor eye-health knowledge and health literacy are pervasive, contributing to worse outcomes. This study aims to examine short- and long-term eye-health knowledge retention following eye-health education interventions in adults. METHODS: Vision Detroit was an outreach vision screening program that integrated a 5-Point Teaching Intervention (5PTI), at a Southwest Community Center (SW-CC) from 2015-2017. The 5PTI consists of eye-health learning points developed to verbally educate patients. During vision screenings, eye-health knowledge tests were administered before and after 5PTI (Test 1 and Test 2, respectively). In 2016, Community Eye-Health Education Interventions (CHEI) were initiated at the SW-CC. During CHEI, bilingual healthcare students taught voluntary SW-CC members the 5PTI learning points, regardless of participant interest to attend future screenings. CHEI sessions occurred on separate dates prior to vision screening events. Test 1 and Test 2 scores were compared for all participants. Test 1 scores were compared for those who underwent CHEI prior to vision screening (CHEI positive) versus those who did not (CHEI negative). RESULTS: Two-hundred-seventeen adult patients met inclusion criteria, with 75.8% women, 82.6% Hispanic, mean age 50.4 ± 16.2 years, 74.6% had high school or less education, and 49.2% had health insurance. Test 1 to Test 2 scores improved after 5PTI (71.2 ± 26.4% vs. 97.2 ± 9.9%, p < .00001). Forty-eight participants attended CHEI and subsequent vision screening. Test 1 scores were higher among those CHEI positive versus CHEI negative (81.1 ± 2.1% vs. 68.3 ± 3.4%, p = .0027). CONCLUSION: Simple eye-health education interventions, delivered during vision screenings and via community-based education, can improve eye-health knowledge.

The Vision Detroit Project: Visual Burden, Barriers, and Access to Eye Care in an Urban Setting.

PURPOSE: Vision loss and blindness are among the top ten disabilities in the United States, yet access and utilization of eye care remains low. Vision Detroit aimed to address eye-care disparities via community-based screenings. By investigating burden of eye disease and barriers to eye-care utilization in an underserved urban community, we may direct efforts to improve access. METHODS: Twenty-three screenings were conducted from March 2015-November 2017. Patient information gathered at screenings were demographics, medical and social history, eye exam/referral history, insurance status, primary care physician (PCP) status, and patient-perceived eye-care barriers. RESULTS: Three-hundred-eighty patients were screened, 42% African American and 51% Hispanic. Average age was 53 ± 16.4 years, 70% reported vision problems, 50% reported over two years of vision problems, and average habitual visual acuity in best-seeing eye was 20/37. Eye-care underutilization was reported in 61% of type-2 diabetics. Older age and PCP recommendations/referrals were associated with increased utilization in all patients. Insurance was the most common barrier (53%); of the 55% insured, 31% reported financial barriers. Employed patients were more likely than unemployed to report a time barrier (odds ratio = 1.76, 95% confidence interval 1.03-3.01). Those with high school or less education reported "unaware of need", "unsure where to go", "transportation", and "insurance" as barriers more often. CONCLUSION: Visual burden was pervasive, yet access was suboptimal. Financial, logistical, and awareness barriers were common. PCP referral and older age were associated with increased utilization. Those less educated reported more barriers, highlighting the need to address fiscal concerns and eye-health education.

Frontotemporal Lobar Dementia Mutant Tau Impairs Axonal Transport through a Protein Phosphatase 1γ-Dependent Mechanism.

Pathologic tau modifications are characteristic of Alzheimer's disease and related dementias, but mechanisms of tau toxicity continue to be debated. Inherited mutations in tau cause early onset frontotemporal lobar dementias (FTLD-tau) and are commonly used to model mechanisms of tau toxicity in tauopathies. Previous work in the isolated squid axoplasm model demonstrated that several pathogenic forms of tau inhibit axonal transport through a mechanism involving activation of protein phosphatase 1 (PP1). Here, we determined that P301L and R5L FTLD mutant tau proteins elicit a toxic effect on axonal transport as monomeric proteins. We evaluated interactions of wild-type or mutant tau with specific PP1 isoforms (α, ß, and γ) to examine how the interaction contributes to this toxic effect using primary rat hippocampal neurons from both sexes. Pull-down and bioluminescence resonance energy transfer experiments revealed selective interactions of wild-type tau with PP1α and PP1γ isoforms, but not PP1ß, which were significantly increased by the P301L tau mutation. The results from proximity ligation assays confirmed the interaction in primary hippocampal neurons. Moreover, expression of FTLD-linked mutant tau in these neurons enhanced levels of active PP1, also increasing the pausing frequency of fluorescently labeled vesicles in both anterograde and retrograde directions. Knockdown of PP1γ, but not PP1α, rescued the cargo-pausing effects of P301L and R5L tau, a result replicated by deleting a phosphatase-activating domain in the amino terminus of P301L tau. These findings support a model of tau toxicity involving aberrant activation of a specific PP1γ-dependent pathway that disrupts axonal transport in neurons.SIGNIFICANCE STATEMENT Tau pathology is closely associated with neurodegeneration in Alzheimer's disease and other tauopathies, but the toxic mechanisms remain a debated topic. We previously proposed that pathologic tau forms induce dysfunction and degeneration through aberrant activation of a PP1-dependent pathway that disrupts axonal transport. Here, we show that tau directly interacts with specific PP1 isoforms, increasing levels of active PP1. Pathogenic tau mutations enhance this interaction, further increasing active PP1 levels and impairing axonal transport in isolated squid axoplasm and primary hippocampal neurons. Mutant-tau-mediated impairment of axonal transport was mediated by PP1γ and a phosphatase-activating domain located at the amino terminus of tau. This work has important implications for understanding and potentially mitigating tau-mediated neurotoxicity in tauopathies.

Sildenafil-evoked photoreceptor oxidative stress in vivo is unrelated to impaired visual performance in mice.

PURPOSE: The phosphodiesterase inhibitor sildenafil is a promising treatment for neurodegenerative disease, but it can cause oxidative stress in photoreceptors ex vivo and degrade visual performance in humans. Here, we test the hypotheses that in wildtype mice sildenafil causes i) wide-spread photoreceptor oxidative stress in vivo that is linked with ii) impaired vision. METHODS: In dark or light-adapted C57BL/6 mice ± sildenafil treatment, the presence of oxidative stress was evaluated in retina laminae in vivo by QUEnch-assiSTed (QUEST) magnetic resonance imaging, in the subretinal space in vivo by QUEST optical coherence tomography, and in freshly excised retina by a dichlorofluorescein assay. Visual performance indices were also evaluated by QUEST optokinetic tracking. RESULTS: In light-adapted mice, 1 hr post-sildenafil administration, oxidative stress was most evident in the superior peripheral outer retina on both in vivo and ex vivo examinations; little evidence was noted for central retina oxidative stress in vivo and ex vivo. In dark-adapted mice 1 hr after sildenafil, no evidence for outer retina oxidative stress was found in vivo. Evidence for sildenafil-induced central retina rod cGMP accumulation was suggested as a panretinally thinner, dark-like subretinal space thickness in light-adapted mice at 1 hr but not 5 hr post-sildenafil. Cone-based visual performance was impaired by 5 hr post-sildenafil and not corrected with anti-oxidants; vision was normal at 1 hr and 24 hr post-sildenafil. CONCLUSIONS: The sildenafil-induced spatiotemporal pattern of oxidative stress in photoreceptors dominated by rods was unrelated to impairment of cone-based visual performance in wildtype mice.

Novel imaging biomarkers for mapping the impact of mild mitochondrial uncoupling in the outer retina in vivo.

PURPOSE: To test the hypothesis that imaging biomarkers are useful for evaluating in vivo rod photoreceptor cell responses to a mitochondrial protonophore. METHODS: Intraperitoneal injections of either the mitochondrial uncoupler 2,4 dinitrophenol (DNP) or saline were given to mice with either higher [129S6/eVTac (S6)] or lower [C57BL/6J (B6)] mitochondrial reserve capacities and were studied in dark or light. We measured: (i) the external limiting membrane-retinal pigment epithelium region thickness (ELM-RPE; OCT), which decreases substantially with upregulation of a pH-sensitive water removal co-transporter on the apical portion of the RPE, and (ii) the outer retina R1 (= 1/(spin lattice relaxation time (T1), an MRI parameter proportional to oxygen / free radical content. RESULTS: In darkness, baseline rod energy production and consumption are relatively high compared to that in light, and additional metabolic stimulation with DNP provoked thinning of the ELM-RPE region compared to saline injection in S6 mice; ELM-RPE thickness was unresponsive to DNP in B6 mice. Also, dark-adapted S6 mice given DNP showed a decrease in outer retina R1 values compared to saline injection in the inferior retina. In dark-adapted B6 mice, transretinal R1 values were unresponsive to DNP in superior and inferior regions. In light, with its relatively lower basal rod energy production and consumption, DNP caused ELM-RPE thinning in both S6 and B6 mice. CONCLUSIONS: The present results raise the possibility of non-invasively evaluating the mouse rod mitochondrial energy ecosystem using new DNP-assisted OCT and MRI in vivo assays.