Super-Resolution Imaging of the Extracellular Space in Living Brain Tissue.

The extracellular space (ECS) of the brain has an extremely complex spatial organization, which has defied conventional light microscopy. Consequently, despite a marked interest in the physiological roles of brain ECS, its structure and dynamics remain largely inaccessible for experimenters. We combined 3D-STED microscopy and fluorescent labeling of the extracellular fluid to develop super-resolution shadow imaging (SUSHI) of brain ECS in living organotypic brain slices. SUSHI enables quantitative analysis of ECS structure and reveals dynamics on multiple scales in response to a variety of physiological stimuli. Because SUSHI produces sharp negative images of all cellular structures, it also enables unbiased imaging of unlabeled brain cells with respect to their anatomical context. Moreover, the extracellular labeling strategy greatly alleviates problems of photobleaching and phototoxicity associated with traditional imaging approaches. As a straightforward variant of STED microscopy, SUSHI provides unprecedented access to the structure and dynamics of live brain ECS and neuropil.

Shadow enhancers modulate distinct transcriptional parameters that differentially effect downstream patterning events.

Transcription in the early Drosophila blastoderm is coordinated by the collective action of hundreds of enhancers. Many genes are controlled by so-called 'shadow enhancers', which provide resilience to environment or genetic insult, allowing the embryo to robustly generate a precise transcriptional pattern. Emerging evidence suggests that many shadow enhancer pairs do not drive identical expression patterns, but the biological significance of this remains unclear. In this study, we characterize the shadow enhancer pair controlling the gene short gastrulation (sog). We removed either the intronic proximal enhancer or the upstream distal enhancer and monitored sog transcriptional kinetics. Notably, each enhancer differs in sog spatial expression, timing of activation and RNA Polymerase II loading rates. In addition, modeling of individual enhancer activities demonstrates that these enhancers integrate activation and repression signals differently. Whereas activation is due to the sum of the two enhancer activities, repression appears to depend on synergistic effects between enhancers. Finally, we examined the downstream signaling consequences resulting from the loss of either enhancer, and found changes in tissue patterning that can be explained by the differences in transcriptional kinetics measured.

Shadowed versus Etched Superconductor-Semiconductor Junctions in Al/InAs Nanowires.

Hybrid semiconductor-superconductor nanowires have emerged as a cornerstone in modern quantum devices. Integrating such nanowires into hybrid devices typically requires extensive postgrowth processing which may affect device performance unfavorably. Here, we present a technique for in situ shadowing superconductors on nanowires and compare the structural and electronic properties of Al junctions formed by shadowing versus etching. Based on transmission electron microscopy, we find that typical etching procedures lead to atomic-scale surface roughening. This surface perturbation may cause a reduction of the electron mobility as demonstrated in transport measurements. Further, we display advanced shadowing geometries aiding in the pursuit of bringing fabrication of hybrid devices in situ. Finally, we give examples of shadowed junctions exploited in various device geometries that exhibit high-quality quantum transport signatures.

Maximum spherical mean value filtering for whole-brain QSM.

PURPOSE: To develop a tissue field-filtering algorithm, called maximum spherical mean value (mSMV), for reducing shadow artifacts in QSM of the brain without requiring brain-tissue erosion. THEORY AND METHODS: Residual background field is a major source of shadow artifacts in QSM. The mSMV algorithm filters large field-magnitude values near the border, where the maximum value of the harmonic background field is located. The effectiveness of mSMV for artifact removal was evaluated by comparing existing QSM algorithms in numerical brain simulation as well as using in vivo human data acquired from 11 healthy volunteers and 93 patients. RESULTS: Numerical simulation showed that mSMV reduces shadow artifacts and improves QSM accuracy. Better shadow reduction, as demonstrated by lower QSM variation in the gray matter and higher QSM image quality score, was also observed in healthy subjects and in patients with hemorrhages, stroke, and multiple sclerosis. CONCLUSION: The mSMV algorithm allows QSM maps that are substantially equivalent to those obtained using SMV-filtered dipole inversion without eroding the volume of interest.

Quantifying HONO Production from Nitrate Photolysis in a Polluted Atmosphere.

The photolysis of particulate nitrate (pNO3-) has been suggested to be an important source of nitrous acid (HONO) in the troposphere. However, determining the photolysis rate constant of pNO3- (jpNO3-) suffers from high uncertainty. Prior laboratory measurements of jpNO3- using aerosol filters have been complicated by the "shadow effect"─a phenomenon of light extinction within aerosol layers that potentially skews these measurements. We developed a method to correct the shadow effect on the photolysis rate constant of pNO3- for HONO production (jpNO3- â†’ HONO) using aerosol filters with identical chemical compositions but different aerosol loadings. We applied the method to quantify jpNO3- â†’ HONO over the North China Plain (NCP) during the winter haze period. After correcting for the shadow effect, the normalized average jpNO3- â†’ HONO at 5 °C increased from 5.89 × 10-6 s-1 to 1.72 × 10-5 s-1. The jpNO3- â†’ HONO decreased with increasing pH and nitrate proportions in PM2.5 and had no correlation with nitrate concentrations. A parametrization for jpNO3- â†’ HONO was developed for model simulation of HONO production in NCP and similar environments.

Synthetic Document Images with Diverse Shadows for Deep Shadow Removal Networks.

Shadow removal for document images is an essential task for digitized document applications. Recent shadow removal models have been trained on pairs of shadow images and shadow-free images. However, obtaining a large, diverse dataset for document shadow removal takes time and effort. Thus, only small real datasets are available. Graphic renderers have been used to synthesize shadows to create relatively large datasets. However, the limited number of unique documents and the limited lighting environments adversely affect the network performance. This paper presents a large-scale, diverse dataset called the Synthetic Document with Diverse Shadows (SynDocDS) dataset. The SynDocDS comprises rendered images with diverse shadows augmented by a physics-based illumination model, which can be utilized to obtain a more robust and high-performance deep shadow removal network. In this paper, we further propose a Dual Shadow Fusion Network (DSFN). Unlike natural images, document images often have constant background colors requiring a high understanding of global color features for training a deep shadow removal network. The DSFN has a high global color comprehension and understanding of shadow regions and merges shadow attentions and features efficiently. We conduct experiments on three publicly available datasets, the OSR, Kligler's, and Jung's datasets, to validate our proposed method's effectiveness. In comparison to training on existing synthetic datasets, our model training on the SynDocDS dataset achieves an enhancement in the PSNR and SSIM, increasing them from 23.00 dB to 25.70 dB and 0.959 to 0.971 on average. In addition, the experiments demonstrated that our DSFN clearly outperformed other networks across multiple metrics, including the PSNR, the SSIM, and its impact on OCR performance.

A Comparative Study of Physically Accurate Synthetic Shadow Datasets in Agricultural Settings with Human Activity.

Shadow, a natural phenomenon resulting from the absence of light, plays a pivotal role in agriculture, particularly in processes such as photosynthesis in plants. Despite the availability of generic shadow datasets, many suffer from annotation errors and lack detailed representations of agricultural shadows with possible human activity inside, excluding those derived from satellite or drone views. In this paper, we present an evaluation of a synthetically generated top-down shadow segmentation dataset characterized by photorealistic rendering and accurate shadow masks. We aim to determine its efficacy compared to real-world datasets and assess how factors such as annotation quality and image domain influence neural network model training. To establish a baseline, we trained numerous baseline architectures and subsequently explored transfer learning using various freely available shadow datasets. We further evaluated the out-of-domain performance compared to the training set of other shadow datasets. Our findings suggest that AgroSegNet demonstrates competitive performance and is effective for transfer learning, particularly in domains similar to agriculture.

CenterNet-Saccade: Enhancing Sonar Object Detection with Lightweight Global Feature Extraction.

Sonar imaging technology is widely used in the field of marine and underwater monitoring because sound waves can be transmitted in elastic media, such as the atmosphere and seawater, without much interference. In underwater object detection, due to the unique characteristics of the monitored sonar image, and since the target in an image is often accompanied by its own shadow, we can use the relative relationship between the shadow and the target for detection. To make use of shadow-information-aided detection and realize accurate real-time detection in sonar images, we put forward a network based on a lightweight module. By using the attention mechanism with a global receptive field, the network can make the target pay attention to the shadow information in the global environment, and because of its exquisite design, the computational time of the network is greatly reduced. Specifically, we design a ShuffleBlock model adapted to Hourglass to make the backbone network lighter. The concept of CNN dimension reduction is applied to MHSA to make it more efficient while paying attention to global features. Finally, CenterNet's unreasonable distribution method of positive and negative samples is improved. Simulation experiments were carried out using the proposed sonar object detection dataset. The experimental results further verify that our improved model has obvious advantages over many existing conventional deep learning models. Moreover, the real-time monitoring performance of our proposed model is more conducive to the implementation in the field of ocean monitoring.

Current-Mode Shadow Filter with Single-Input Multiple-Output Using Current-Controlled Current Conveyors with Controlled Current Gain.

In this paper, a novel current-mode shadow filter employing current-controlled current conveyors (CCCIIs) with controlled current gains is presented. The CCCII-based current-mode shadow filters are resistorless and can offer a number of advantages such as circuit simplicity and electronic tuning capability. The proposed shadow filters offer five filtering functions, i.e., low-pass, high-pass, band-pass, band-stop, and all-pass functions, in the same topology. Furthermore, no component matching condition is required to realize all the transfer functions. The natural frequency and quality factor adjustment is possible by using the CCCII current gains without the need to use external amplifiers, all capacitors are grounded, and the filter terminals offer low-input and high-output impedance. To verify the functionality and feasibility of the new topologies, the proposed circuits were simulated using SPICE and the transistor model process parameters NR100N (NPN) and PR100N (PNP) from AT&T's bipolar arrays ALA400-CBIC-R. The simulation results are consistent with the theory. The CCCII experimental setup was designed using commercially available 2N3904 (NPN) and 2N3906 (PNP) transistors with a supply voltage of ±2.5 V. The measurement results confirm the performance of the designed filters.

Accuracy Assessment of Geometric-Distortion Identification Methods for Sentinel-1 Synthetic Aperture Radar Imagery in Highland Mountainous Regions.

SAR imagery plays a crucial role in geological and environmental monitoring, particularly in highland mountainous regions. However, inherent geometric distortions in SAR images often undermine the precision of remote sensing analyses. Accurately identifying and classifying these distortions is key to analyzing their origins and enhancing the quality and accuracy of monitoring efforts. While the layover and shadow map (LSM) approach is commonly utilized to identify distortions, it falls short in classifying subtle ones. This study introduces a novel LSM ground-range slope (LG) method, tailored for the refined identification of minor distortions to augment the LSM approach. We implemented the LG method on Sentinel-1 SAR imagery from the tri-junction area where the Xiaojiang, Pudu, and Jinsha rivers converge at the Yunnan-Sichuan border. By comparing effective monitoring-point densities, we evaluated and validated traditional methods-LSM, R-Index, and P-NG-against the LG method. The LG method demonstrates superior performance in discriminating subtle distortions within complex terrains through its secondary classification process, which allows for precise and comprehensive recognition of geometric distortions. Furthermore, our research examines the impact of varying slope parameters during the classification process on the accuracy of distortion identification. This study addresses significant gaps in recognizing geometric distortions and lays a foundation for more precise SAR imagery analysis in complex geographic settings.

Validation of a 3D Local-Scale Adaptive Solar Radiation Model by Using Pyranometer Measurements and a High-Resolution Digital Elevation Model.

The result of the multidisciplinary collaboration of researchers from different areas of knowledge to validate a solar radiation model is presented. The MAPsol is a 3D local-scale adaptive solar radiation model that allows us to estimate direct, diffuse, and reflected irradiance for clear sky conditions. The model includes the adaptation of the mesh to complex orography and albedo, and considers the shadows cast by the terrain and buildings. The surface mesh generation is based on surface refinement, smoothing and parameterization techniques and allows the generation of high-quality adapted meshes with a reasonable number of elements. Another key aspect of the paper is the generation of a high-resolution digital elevation model (DEM). This high-resolution DEM is constructed from LiDAR data, and its resolution is two times more accurate than the publicly available DEMs. The validation process uses direct and global solar irradiance data obtained from pyranometers at the University of Salamanca located in an urban area affected by systematic shading from nearby buildings. This work provides an efficient protocol for studying solar resources, with particular emphasis on areas of complex orography and dense buildings where shadows can potentially make solar energy production facilities less efficient.

Sn/InAs Josephson Junctions on Selective Area Grown Nanowires with in Situ Shadowed Superconductor Evaporation.

Superconductor-semiconductor nanowire hybrid structures are useful in fabricating devices for quantum information processing. While selective area growth (SAG) offers the flexibility to grow semiconductor nanowires in arbitrary geometries, in situ evaporation of superconductors ensures pristine superconductor-semiconductor interfaces, resulting in strong induced superconductivity in the semiconducting nanowire. In this work, we used high-aspect-ratio SiOx dielectric walls to in situ evaporate islands of superconductor tin on in-plane InAs SAG nanowires. Our technique enables customization in the designs of such hybrid nanostructures, while simultaneously performing the nanowire and superconductor growth without breaking vacuum. Using this technique, we grew super(S)-normal(N)-super(S), NS, and SNSNS junctions. We performed cryogenic electron transport measurements revealing the presence of gate and field tunable supercurrents. We further measured the superconducting gap and critical fields in the hybrid nanostructures and the crossover from 2e to 1e periodicity in the SNSNS junctions as a proof of the usability of these hybrid nanostructures.

Shadow prices of agrochemicals in the Chinese farming sector: A convex expectile regression approach.

The use of agrochemical inputs has significantly enhanced agricultural yields in China; however, their excessive utilization has also caused a range of environmental issues. This paper examines the costs associated with reducing agrochemicals by employing shadow prices, which represent the value of the marginal product of agrochemicals, to further develop cost-effective environmental policy measures for reducing their usage. To this end, the shadow prices of agrochemicals have been assessed by adopting a newly developed convex expectile regression approach and using statistical data from 31 provinces in China spanning from 2005 to 2020. Furthermore, the present study investigates the disparities between shadow prices and market prices for different agrochemicals across various regions in China. The findings suggest that the costs of reducing chemical fertilizers are higher than those of reducing pesticides and plastic films. Moreover, the results indicate that central China exhibits relatively high potential for decreasing agrochemical usage. Finally, these findings can inform the Chinese government's restructuring of producer support and environmental policy in a cost-effective way to mitigate agrochemicals use in the future. Additionally, the research method employed in this study holds potential for extension to other agrochemicals-dependent countries.

Acoustic Shadowing to Facilitate Ultrasound Guided Arterial Cannulation: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

Aim and background: Ultrasound-guided arterial catheterization is a frequently performed procedure. Additional techniques such as acoustic shadowing-assisted ultrasound may be useful in improving success rate. This systematic review aimed to assess the efficacy of acoustic shadowing assisted ultrasound for arterial catheterization. Materials and methods: PubMed, Medline, EMBASE, Cochrane Library, EMCARE, and MedNar were searched in January 2024. Randomized controlled trials comparing the first attempt success rate of arterial catheterization using acoustic shadowing ultrasound vs unassisted ultrasound were included. Data were pooled for risk ratios (RRs) using the random-effects model. Subgroup analysis was conducted based on a single or double acoustic line. Sensitivity analysis was undertaken after excluding pediatric data. The certainty of evidence (COE) was assessed using the GRADE framework. Results: Six randomized controlled trials (n = 777) were included. A meta-analysis found the first attempt success rate is significantly higher in the acoustic ultrasound group (n = 6, RR: 0.47, 95% CI: 0.34-0.66, p ≤ 0.00001). Hematoma formation was significantly less in the acoustic ultrasound group (n = 6, RR: 0.52, 95% CI: 0.34-0.80, p = 0.003). First attempt success was significantly higher in the single acoustic line ultrasound (USG) group compared to the unassisted ultrasound group (n = 3, RR: 0.41, 95% CI: 0.28-0.59, p ≤ 0.00001). Sensitivity analysis after excluding pediatric data was similar to the primary analysis (n = 5, RR: 0.50, 95% CI: 0.33-0.70, p ≤ 0.00001). Certainty of evidence was "Moderate" for the first attempt cannulation. Conclusions: Acoustic shadowing-assisted ultrasound improved first-attempt arterial catheterization success rate and was associated with reduced hematoma formation. How to cite this article: Mishra L, Rath C, Wibrow B, Anstey M, Ho K. Acoustic Shadowing to Facilitate Ultrasound Guided Arterial Cannulation: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Indian J Crit Care Med 2024;28(7):677-685.

[Study on evaluation method of circular small shadow profusion in chest CT reconstruction images of pneumoconiosis].

Objective: To select chest CT image patterns for the diagnosis of pneumoconiosis and establish a method for determining the profusion of circular small shadows in chest CT. Methods: In April 2021, 66 cases of occupational pneumoconiosis patients with digital radiography (DR) chest radiographs and chest CT imaging data with circular small shadow as the main manifestations were selected as the study objects. 1.5 mm and 5 mm chest CT axial images, 1 mm and 5 mm chest CT coronal multi-plane recombination (MPR) images, and 5 mm chest CT coronal maximum intensity projection (MIP) images were used to observe the different characteristics of pneumoconiosis patients, and were compared and analyzed with DR chest radiographs to establish the experimental chest CT standards. The consistency of the profusion results between the experimental chest CT standards and GBZ 70-2015 Diagnosis of Occupational Pneumoconiosis was verified. Results: All the 66 objects were male, including 33 cases of stage Ⅰ pneumoconiosis, 17 cases of stage Ⅱ pneumoconiosis and 16 cases of stage Ⅲ pneumoconiosis. By observing five chest CT images of 66 objects, we found that chest CT images of different modes could clearly display and identify abnormal images such as small circular shadow, large shadow, small shadow aggregation, honeycomb glass shadow, flake glass shadow, uniform low-profusion glass shadow, mesh glass shadow, cable shadow, linear shadow, subpleural spinous shadow, subpleural nodules, various kinds of emphysema and lung texture distortion and fracture. Small shadow aggregation was usually accompanied by the appearance of large shadow. The vascular shadows in 5 mm CT images had good ductility, and small nodules were easy to distinguish. The coronal MIP image of 5 mm chest CT used edge enhancement technology, which was prone to small shadow fusion and fibrotic shadow fusion. The coronal MPR image of 5 mm chest CT was highly consistent with the DR chest radiographs in terms of the integrity of film reading. GBZ 70-2015 standard was used to compare the profusion of DR chest radiographs and 5 mm chest CT coronal MPR images of 66 objects, and the consistency test Kappa=0.64. GBZ 70-2015 standard and experimental chest CT standard were used to compare the profusion results of DR chest radiographs and 5 mm chest CT coronal MPR images of 66 objects, respectively, and the consistency test Kappa=0.80, with high consistency. Conclusion: 5 mm coronal MPR image is suitable for chest CT imaging in the diagnosis of pneumoconiosis. Following the selection path and method of GBZ 70-2015 profusion criterion, the established experimental chest CT standard in determining the profusion of small circular shadows in 5 mm coronal MPR images of chest CT with pneumoconiosis has a high consistency with GBZ 70-2015 standard.

Comparative and experimental studies on the relationship between body size and countershading in caterpillars.

Countershading is a gradient of colouration in which the illuminated dorsal surfaces are darker than the unilluminated ventral surface. It is widespread in the animal kingdom and endows the body with a more uniform colour to decrease the chance of detection by predators. Although recent empirical studies support the theory of survival advantage conferred by countershading, this camouflage strategy has evolved only in some of the cryptic animals, and our understanding of the factors that affect the evolution of countershading is limited. This study examined the association between body size and countershading using lepidopteran larvae (caterpillars) as a model system. Specifically, we predicted that countershading may have selectively evolved in large-sized species among cryptic caterpillars if (1) large size constrains camouflage which facilitates the evolution of a trait reinforcing their crypsis and (2) the survival advantage of countershading is size-dependent. Phylogenetic analyses of four different lepidopteran families (Saturniidae, Sphingidae, Erebidae, and Geometridae) suggest equivocal results: countershading was more likely to be found in larger species in Saturniidae but not in the other families. The field predation experiment assuming avian predators did not support size-dependent predation in countershaded prey. Collectively, we found only weak evidence that body size is associated with countershading in caterpillars. Our results suggest that body size is not a universal factor that has shaped the interspecific variation in countershading observed in caterpillars.

Cell adhesion molecule L1 interacts with the chromo shadow domain of heterochromatin protein 1 isoforms α, ß, and É£ via its intracellular domain.

Cell adhesion molecule L1 regulates multiple cell functions and L1 deficiency is linked to several neural diseases. Proteolytic processing generates functionally decisive L1 fragments, which are imported into the nucleus. By computational analysis, we found at L1's C-terminal end the chromo shadow domain-binding motif PxVxL, which directs the binding of nuclear proteins to the heterochromatin protein 1 (HP1) isoforms α, ß, and É£. By enzyme-linked immunosorbent assay, we show that the intracellular L1 domain binds to all HP1 isoforms. These interactions involve the HP1 chromo shadow domain and are mediated via the sequence 1158 KDET1161 in the intracellular domain of murine L1, but not by L1's C-terminal PxVxL motif. Immunoprecipitation using nuclear extracts from the brain and from cultured cerebellar and cortical neurons indicates that HP1 isoforms interact with a yet unknown nuclear L1 fragment of approximately 55 kDa (L1-55), which carries ubiquitin residues. Proximity ligation indicates a close association between L1-55 and the HP1 isoforms in neuronal nuclei. This association is reduced after the treatment of neurons with inhibitors of metalloproteases, ß-site of amyloid precursor protein cleaving enzyme (BACE1), or É£-secretase, suggesting that cleavage of full-length L1 by these proteases generates L1-55. Reduction of HP1α, -ß, or -É£ expression by siRNA decreases L1-dependent neurite outgrowth from cultured cortical neurons and decreases the L1-dependent migration of L1-transfected HEK293 cells in a scratch assay. These findings indicate that the interaction of the novel fragment L1-55 with HP1 isoforms in nuclei affects L1-dependent functions, such as neurite outgrowth and neuronal migration.

Non-parametric inference about mean functionals of non-ignorable non-response data without identifying the joint distribution.

We consider identification and inference about mean functionals of observed covariates and an outcome variable subject to non-ignorable missingness. By leveraging a shadow variable, we establish a necessary and sufficient condition for identification of the mean functional even if the full data distribution is not identified. We further characterize a necessary condition for n-estimability of the mean functional. This condition naturally strengthens the identifying condition, and it requires the existence of a function as a solution to a representer equation that connects the shadow variable to the mean functional. Solutions to the representer equation may not be unique, which presents substantial challenges for non-parametric estimation, and standard theories for non-parametric sieve estimators are not applicable here. We construct a consistent estimator of the solution set and then adapt the theory of extremum estimators to find from the estimated set a consistent estimator of an appropriately chosen solution. The estimator is asymptotically normal, locally efficient and attains the semi-parametric efficiency bound under certain regularity conditions. We illustrate the proposed approach via simulations and a real data application on home pricing.

The evolution of narrative identity in a "returning home" man: The psychological and cultural place of farming in the Chinese psyche.

OBJECTIVE: This study attempts to illustrate the process of reconstructing adaptive self-identity by tracking the development of imagery in Mr. Z's dreams and sandtrays. METHOD: The authors adopted amplification and Narrative Identity Process Analysis methods, and developed an Imagery NPCS tool to analyze the farming images in therapy sessions. RESULTS: It provided insights into Chinese culture from an applied, non-Western lens on identity theory. The subject of the study was a Chinese man who had lost his social identity due to stressful events, the results of which were reflected in the interplay between his personal narrative related to farming images and their cultural narrative framework. CONCLUSIONS: The authors propose a practical mode of developing narrative identity based on the dynamic organizing principle of opposites which are united in a persona-shadow personality system. Development of an integrated narrative identity can be facilitated by the dialectic between the cultural narrative offered by the psychotherapist and the client's personal narrative.

The Atoh7 remote enhancer provides transcriptional robustness during retinal ganglion cell development.

The retinal ganglion cell (RGC) competence factor ATOH7 is dynamically expressed during retinal histogenesis. ATOH7 transcription is controlled by a promoter-adjacent primary enhancer and a remote shadow enhancer (SE). Deletion of the ATOH7 human SE causes nonsyndromic congenital retinal nonattachment (NCRNA) disease, characterized by optic nerve aplasia and total blindness. We used genome editing to model NCRNA in mice. Deletion of the murine SE reduces Atoh7 messenger RNA (mRNA) fivefold but does not recapitulate optic nerve loss; however, SEdel/knockout (KO) trans heterozygotes have thin optic nerves. By analyzing Atoh7 mRNA and protein levels, RGC development and survival, and chromatin landscape effects, we show that the SE ensures robust Atoh7 transcriptional output. Combining SE deletion and KO and wild-type alleles in a genotypic series, we determined the amount of Atoh7 needed to produce a normal complement of adult RGCs, and the secondary consequences of graded reductions in Atoh7 dosage. Together, these data reveal the workings of an evolutionary fail-safe, a duplicate enhancer mechanism that is hard-wired in the machinery of vertebrate retinal ganglion cell genesis.