Proteins of the bone morphogenetic protein (BMP) family are known to have a role in ocular and skeletal development; however, because of their widespread expression and functional redundancy, less progress has been made identifying the roles of individual BMPs in human disease. We identified seven heterozygous mutations in growth differentiation factor 6 (GDF6), a member of the BMP family, in patients with both ocular and vertebral anomalies, characterized their effects with a SOX9-reporter assay and western analysis, and demonstrated comparable phenotypes in model organisms with reduced Gdf6 function. We observed a spectrum of ocular and skeletal anomalies in morphant zebrafish, the latter encompassing defective tail formation and altered expression of somite markers noggin1 and noggin2. Gdf6(+/-) mice exhibited variable ocular phenotypes compatible with phenotypes observed in patients and zebrafish. Key differences evident between patients and animal models included pleiotropic effects, variable expressivity and incomplete penetrance. These data establish the important role of this determinant in ocular and vertebral development, demonstrate the complex genetic inheritance of these phenotypes, and further understanding of BMP function and its contributions to human disease.

BackgroundVision is initiated by phototransduction in the outer retina by photoreceptors, whose high metabolic rate generates large CO2 loads. Inner retina cells then process the visual signal and CO2. The anion exchanger 3 gene (AE3/Slc4a3) encodes full-length AE3 (AE3fl) and cardiac AE3 (AE3c) isoforms, catalyzing plasma membrane Cl−/HCO3 − exchange in Müller (AE3fl) and horizontal (AE3c) cells. AE3 thus maintains acid-balance by removing photoreceptor-generated CO2 waste.Methodology/Principal FindingsWe report that Slc4a3−/− null mice have inner retina defects (electroretinogram b-wave reduction, optic nerve and retinal vessel anomalies). These pathologic features are common to most human vitreoretinal degenerations. Immunobloting analysis revealed that Na+/HCO3 − co-transporter (NBC1), and carbonic anhydrase II and CAXIV, protein expression were elevated in Slc4a3 −/− mouse retinas, suggesting compensation for loss of AE3. TUNEL staining showed increased numbers of apoptotic nuclei from 4–6 months of age, in Slc4a3 −/− mice, indicating late onset photoreceptor death.Conclusions/SignificanceIdentification of Slc4a3 as underlying a previously unrecognized cause of blindness suggests this gene as a new candidate for a subset of hereditary vitreoretinal retinal degeneration.

Purpose. To investigate the impact of progressive age-related photoreceptor degeneration on retinal integrity in Stargardt-like macular dystrophy (STGD3). Methods. The structural design of the inner retina of the ELOVL4 transgenic mouse model of STGD3 was compared with that of age-matched littermate wild-type (WT) mice from 1 to 24 months of age by using immunohistofluorescence and confocal microscopy and by relying on antibodies against cell-type-specific markers, synapse-associated proteins, and neurotransmitters. Results. Müller cell reactivity occurred at the earliest age studied, before photoreceptor loss. This finding is perhaps not surprising, considering the cell's ubiquitous roles in retina homeostasis. Second-order neurons displayed salient morphologic changes as a function of photoreceptoral input loss. Age-related sprouting of dendritic fibers from rod bipolar and horizontal cells into the ONL did not occur. In contrast, with the loss of photoreceptor sensory input, these second-order neurons progressively bore fewer synapses. After rod loss, the few remaining cones showed abnormal opsin expression, revealing tortuous branched axons. After complete ONL loss (beyond 18 months of age), localized areas of extreme retinal disruptions were observed in the central retina. RPE cell invasion, dense networks of strongly reactive Müller cell processes, and invagination of axons and blood vessels were distinctive features of these regions. In addition, otherwise unaffected cholinergic amacrine cells displayed severe perturbation of their cell bodies and synaptic plexi in these areas. Conclusions. Remodeling in ELOVL4 transgenic mice follows a pattern similar to that reported after other types of hereditary retinopathies in animals and humans, pointing to a potentially common pathophysiologic mechanism.

Unlike laboratory rats and mice, muridae of the Arvicanthis family (A. ansorgei and A. niloticus) are adapted to functioning best in daylight. To date, they have been used as experimental models mainly in studies of circadian rhythms. However, recent work aimed at optimizing photoreceptor-directed gene delivery vectors (Khani et al. [2007] Invest Ophthalmol Vis Sci 48:3954-3961) suggests their potential usefulness for studying retinal pathologies and therapies. In the present study we analyzed the retinal anatomy and visual performance of the Nile grass rat (A. niloticus) using immunohistofluorescence and the optokinetic response (OKR). We found that approximately 35-40% of photoreceptors are cones; that many neural features of the inner retina are similar to those in other diurnal mammals; and that spatial acuity, measured by the OKR, is more than two times that of the usual laboratory rodents. These observations are consistent with the known diurnal habits of this animal, and further support its pertinence as a complementary model for studies of structure, function, and pathology in cone-rich mammalian retinae.

Setting Shambhala is a 5-day electronic dance music (EDM) festival held in rural British Columbia that annually hosts between 15,000 and 18,000 people on a 500-acre ranch. The AIDS Network Outreach & Support Society (ANKORS) has provided harm reduction services throughout the duration of the festival since 2003, including point-of-care drug checking, which allows realtime testing of illicit substances to assess their composition. Drug checking results are provided directly to clients and displayed in aggregate on a screen for all attendees to see. Intervention In 2017, ANKORS added fentanyl checking to their repertoire of drug checking technologies for festivalgoers. Volunteers used a brief survey to collect information on what clients expected the samples to contain. Volunteers carried out drug checks and subsequently logged test results. ANKORS provided an amnesty bin at the tent for clients who chose to discard their substances. Outcomes Of the 2683 surveys, 2387 included data on both the client's belief and the actual test result. Clients were more likely to discard when the test result differed from their belief (5.16%) than when their belief was confirmed (0.69%). Discarding increased to 15.54% when the test could not clearly identify a substance and to 30.77% if the client did not have a prior belief of the substance. Of 1971 samples tested for fentanyl, 31 tested positive and 16.13% of clients discarded compared to 2.63% in the negative group. Implications Drug checking services appeal to festivalgoers who, when faced with uncertainty, may discard their substances. This innovative harm reduction service allows for a personalized risk discussion, potentially reaching others via word-of-mouth and early warning systems. Résumé Contexte Shambhala est un festival de musique électronique qui se déroule sur cinq jours dans un ranch de 500 acres en campagne britanno-colombienne et qui accueille de 15 000 à 18 000 personnes. L'AIDS Network Outreach & Support Society (ANKORS) offre des services de réduction des méfaits pour toute la durée du festival depuis 2003, notamment sous forme d'analyses en temps réel de la composition de substances illicites dans des points de service. Les résultats sont remis directement aux clients et affichés sous leur forme brute dans un tableau général que peuvent voir tous les festivaliers.