Protein Phosphatase 2A with B' specificity subunits regulates the Hippo-Yorkie signaling axis in the Drosophila eye disc.

Hippo-Yorkie (Hpo-Yki) signaling is central to diverse developmental processes. Although its redeployment has been amply demonstrated, its context-specific regulation remains poorly understood. The Drosophila eye disc is a continuous epithelium folded into two layers, the peripodial epithelium (PE) and the retinal progenitor epithelium. Here, Yki acts in the PE, first to promote PE identity by suppressing retina fate, and subsequently to maintain proper disc morphology. In the latter process, loss of Yki results in the displacement of a portion of the differentiating retinal epithelium onto the PE side. We show that Protein Phosphatase 2A (PP2A) complexes comprising different substrate-specificity B-type subunits govern the Hpo-Yki axis in this context. These include holoenzymes containing the B‴ subunit Cka and those containing the B' subunits Wdb or Wrd. Whereas PP2A(Cka), as part of the STRIPAK complex, is known to regulate Hpo directly, PP2A(Wdb) acts genetically upstream of the antagonistic activities of the Hpo regulators Sav and Rassf. These in vivo data provide the first evidence of PP2A(B') heterotrimer function in Hpo pathway regulation and reveal pathway diversification at distinct developmental times in the same tissue.

Quantitation of Atmospheric Suspended Polystyrene Nanoplastics by Active Sampling Prior to Pyrolysis-Gas Chromatography-Mass Spectrometry.

Plastic has been demonstrated to release nanoplastics (NPs) into the atmosphere under sunlight irradiation, posing a continuous health risk to the respiratory system. However, due to lack of reliable quantification methods, the occurrence and distribution of NPs in the atmosphere remain unclear. Polystyrene (PS) micro- and nanoplastics (MNPs) represent a crucial component of atmospheric MNPs. In this study, we proposed a simple and robust method for determining the concentration of atmospheric PS NPs using pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). Following active sampling, the filter membrane is directly ground and introduced into the Py-GC/MS system to quantify PS NPs. The proposed method demonstrates excellent reproducibility and high sensitivity, with a detection limit as low as down to 15 pg/m3 for PS NPs. By using this method, the occurrence of PS NPs in both indoor and outdoor atmospheres has been confirmed. Furthermore, the results showed that the abundance of outdoor PS NPs was significantly higher than that of indoor samples, and there was no significant difference in NP vertical distribution within a height of 28.6 m. This method can be applied for the routine monitoring of atmospheric PS NPs and for evaluating their risk to human health.

STRIPAK-PP2A regulates Hippo-Yorkie signaling to suppress retinal fate in the Drosophila eye disc peripodial epithelium.

The specification of organs, tissues and cell types results from cell fate restrictions enacted by nuclear transcription factors under the control of conserved signaling pathways. The progenitor epithelium of the Drosophila compound eye, the eye imaginal disc, is a premier model for the study of such processes. Early in development, apposing cells of the eye disc are established as either retinal progenitors or support cells of the peripodial epithelium (PE), in a process whose genetic and mechanistic determinants are poorly understood. We have identified protein phosphatase 2A (PP2A), and specifically a STRIPAK-PP2A complex that includes the scaffolding and substrate-specificity components Cka, Strip and SLMAP, as a critical player in the retina-PE fate choice. We show that these factors suppress ectopic retina formation in the presumptive PE and do so via the Hippo signaling axis. STRIPAK-PP2A negatively regulates Hippo kinase, and consequently its substrate Warts, to release the transcriptional co-activator Yorkie into the nucleus. Thus, a modular higher-order PP2A complex refines the activity of this general phosphatase to act in a precise specification of cell fate.

Digestive Elimination of Coexisting Microplastics for Determination of Particulate Black Carbon in Environmental Waters.

Determination of particulate black carbon (PBC) in the environment is of great importance but faces a new challenge due to the increasing occurrence of coexisting microplastics (MPs), which are an emerging contaminant with properties very similar to those of PBC and cannot be discriminated in the chemical digestion procedure of the reported PBC analysis method. Herein, a comprehensive method has been developed for accurately determining PBC by digestive elimination of the coexisting MPs and other non-black carbon organic matter. Water samples were filtered with a glass fiber membrane (0.3 µm pore size), and the collected substances with the membrane were subjected to sulfonation with chlorosulfonic acid and Fenton digestion in sequence and then to the total organic carbon analyzer for quantification of PBC. Under the optimized conditions, MPs of various sizes and polymer types were efficiently eliminated (>91.0%), whereas various PBC samples were undigested with recoveries over 91.7% except for the relatively low recovery of 65.6% for the PBC prepared at a low pyrolysis temperature of 400 °C. The feasibility of the proposed method was verified by analysis of real water samples with a spike recovery of 88.6-100.2%. We anticipate that this work will pave an avenue for reliable determination of PBC in the presence of MPs.

Monodisperse amino-modified nanosized zero-valent iron for selective and recyclable removal of TNT: Synthesis, characterization, and removal mechanism.

Nitroaromatic explosives are major pollutants produced during wars that cause serious environmental and health problems. The removal of a typical nitroaromatic explosive, 2,4,6-trinitrotoluene (TNT), from aqueous solution, was conducted using a new recyclable magnetic nano-adsorbent (Fe@SiO2NH2). This adsorbent was prepared by grafting amino groups onto Fe@SiO2 particles with a well-defined core-shell structure and demonstrated monodispersity in solution. The removal performance of the nano-adsorbent towards TNT was found to be 2.57 and 4.92 times higher than that towards two analogous explosives, 2,4-dinitrotoluene (2,4-DNT) and 2-nitrotoluene (2-NT), respectively, under neutral conditions. The difference in the removal performance among the three compounds was further compared in terms of the effects of different conditions (pH value, ionic strength, humic acid concentration, adsorbent modification degree and dosage, etc.) and the electrostatic potential distributions of the three compounds. The most significant elevation is owing to modification of amino on Fe@SiO2 which made a 20.7% increase in adsorption efficiency of TNT. The experimental data were well fit by the pseudo-second-order kinetic model and the Freundlich adsorption isotherm model, indicating multilayer adsorption on a heterogeneous surface. The experimental results and theoretical considerations show that the interactions between Fe@SiO2NH2 NPs and TNT correspond to dipole-dipole and hydrophobic interactions. These interactions should be considered in the design of an adsorbent. Furthermore, the adaptability to aqueous environment and excellent regeneration capacity of Fe@SiO2NH2 NPs makes these remediation materials promising for applications.

Magnetic polyamidoamine dendrimers for magnetic separation and sensitive determination of organochlorine pesticides from water samples by high-performance liquid chromatography.

Organochlorine pesticides (OCPs) have received much attention due to their toxicity. Reliable methods to monitor their residues in the environment are needed. Here, magnetic polyamidoamine dendrimers were prepared by co-precipitation, Michael addition, and amidation. The magnetic polyamidoamine dendrimers demonstrated good adsorption ability for OCPs-this feature was utilized to construct a sensitive tool for monitoring OCPs in water samples. The proposed method provided remarkable linearity from 0.1 to 500 µg/L and satisfactory limits of detection from 0.012 to 0.029 µg/L. The spiked recoveries of the four target analytes were 91.8%-103.5% with relative standard deviations less than 4.5%. The magnetic materials had good reusability. The results indicated that the resulting method was an efficient, easy, rapid, economical, and eco-friendly tool for monitoring OCPs in aqueous samples.

Preparation of magnetic core-shell Fe3O4@polyaniline composite material and its application in adsorption and removal of tetrabromobisphenol A and decabromodiphenyl ether.

Present study described a magnetic adsorption and removal method with prepared magnetic core-shell Fe3O4@polyaniline microspheres for the removal of two typical BFRs, tetrabromobisphenol-A (TBBPA) and decabromodiphenyl ether (BDE-209) from water samples. Magnetic core-shell Fe3O4@polyaniline microspheres were prepared by a hydrothermal and two step polymerization method with cheap iron salts and aniline, which were characterized with transmission electron microscopic (TEM) and scanning electron microscopy (SEM). The results showed that the Fe3O4@polyaniline microspheres earned a clear thickness shell of polyaniline (about 50 nm) and a saturation magnetization of 40.4 emu g-1. The Magnetic core-shell Fe3O4@polyaniline exhibited excellent adsorption capability and removal rate to TBBPA and BDE 209. The adsorption of TBBPA and BDE 209 all followed pseudo-second order kinetics and agreed well to the Freundlich adsorption isotherms model. The negative Gibbs free energy change (ΔG0) and positive standard enthalpy change (ΔH0) for TBBPA and BDE-209 suggested that the adsorption was spontaneous and endothermic in nature. These results demonstrated that Fe3O4@PANI was a good adsorbent and would have a good application prospect in the removal of pollutants from environmental water.

Improved photoelectrocatalytic degradation of tetrabromobisphenol A with silver and reduced graphene oxide-modified TiO2 nanotube arrays under simulated sunlight.

In present study, reductive graphene oxide and silver nanoparticles co-comodified TiO2 nanotube arrays were prepared, and which was investigated to degrade tetrabromobisphenol A. The arrays co-modified with silver nanoparticles and reductive graphene oxide prepared by electrodeposition method exhibited good photoelectrocatalytic degradative activity for tetrabromobisphenol A, and the degradation efficiency reached 99.6% within 80 min. The synergistic effect of high photoresponse of Ag nanoparticles with their high capture ability for photogenerated electrons and the extended wavelength absorption range of reductive graphene oxide resulted in the highest degradation efficiencies. Degradation is postulated to follow a stepwise reductive debromination mechanism.

Distinct regulation of atonal in a visual organ of Drosophila: Organ-specific enhancer and lack of autoregulation in the larval eye.

Drosophila has three types of visual organs, the larval eyes or Bolwig's organs (BO), the ocelli (OC) and the compound eyes (CE). In all, the bHLH protein Atonal (Ato) functions as the proneural factor for photoreceptors and effects the transition from progenitor cells to differentiating neurons. In this work, we investigate the regulation of ato expression in the BO primordium (BOP). Surprisingly, we find that ato transcription in the BOP is entirely independent of the shared regulatory DNA for the developing CE and OC. The core enhancer for BOP expression, atoBO, lies ~6kb upstream of the ato gene, in contrast to the downstream location of CE and OC regulatory elements. Moreover, maintenance of ato expression in the neuronal precursors through autoregulation-a common and ancient feature of ato expression that is well-documented in eyes, ocelli and chordotonal organs-does not occur in the BO. We also show that the atoBO enhancer contains two binding sites for the transcription factor Sine oculis (So), a core component of the progenitor specification network in all three visual organs. These binding sites function in vivo and are specifically bound by So in vitro. Taken together, our findings reveal that the control of ato transcription in the evolutionarily derived BO has diverged considerably from ato regulation in the more ancestral compound eyes and ocelli, to the extent of acquiring what appears to be a distinct and evolutionarily novel cis-regulatory module.

A Comparative Study of Albumin-Bilirubin Score with Child-Pugh Score, Model for End-Stage Liver Disease Score and Indocyanine Green R15 in Predicting Posthepatectomy Liver Failure for Hepatocellular Carcinoma Patients.

BACKGROUND: The albumin-bilirubin (ALBI) grade is a newly proposed model for assessing the hepatic function. This study aimed to compare the value of the ALBI score with Child-Pugh score, model for end-stage liver disease (MELD) score and indocyanine green (ICG) R15 in predicting posthepatectomy liver failure (PHLF). METHODS: Patients undergoing curative resection for hepatocellular carcinoma (HCC) between January 2014 and June 2017 were enrolled. The values of the Child-Pugh score, MELD score, ICG R15 and ALBI score in predicting PHLF were evaluated. RESULTS: A total of 473 HCC patients were enrolled. The ALBI score was identified as an independent predictor of PHLF. The AUCs for the Child-Pugh score, MELD score, ICG R15 and ALBI score in predicting PHLF were 0.665, 0.649, 0.668, and 0.745 respectively. Multivariable analyses revealed that the ALBI score was an independent predictor of PHLF regardless of the hepatectomy subgroups, but the Child-Pugh score and MELD score were not significant predictors of PHLF both in major and minor hepatectomy subgroups, and ICG R15 was only a significant predictor of PHLF in minor hepatectomy subgroup. CONCLUSION: The ALBI score showed superior predictive value of PHLF over Child-Pugh score, MELD score and ICG R15. We propose to use the ALBI score to evaluate surgical risk for HCC patients undergoing hepatic resection.

Fly LMBR1/LIMR-type protein Lilipod promotes germ-line stem cell self-renewal by enhancing BMP signaling.

Limb development membrane protein-1 (LMBR1)/lipocalin-interacting membrane receptor (LIMR)-type proteins are putative nine-transmembrane receptors that are evolutionarily conserved across metazoans. However, their biological function is unknown. Here, we show that the fly family member Lilipod (Lili) is required for germ-line stem cell (GSC) self-renewal in the Drosophila ovary where it enhances bone morphogenetic protein (BMP) signaling. lili mutant GSCs are lost through differentiation, and display reduced levels of the Dpp transducer pMad and precocious activation of the master differentiation factor bam. Conversely, overexpressed Lili induces supernumerary pMad-positive bamP-GFP-negative GSCs. Interestingly, differentiation of lili mutant GSCs is bam-dependent; however, its effect on pMad is not. Thus, although it promotes stem cell self-renewal by repressing a bam-dependent process, Lilipod enhances transduction of the Dpp signal independently of its suppression of differentiation. In addition, because Lili is still required by a ligand-independent BMP receptor, its function likely occurs between receptor activation and pMad phosphorylation within the signaling cascade. This first, to our knowledge, in vivo characterization of a LMBR1/LIMR-type protein in a genetic model reveals an important role in modulating BMP signaling during the asymmetric division of an adult stem cell population and in other BMP signaling contexts.

Shared and distinct mechanisms of atonal regulation in Drosophila ocelli and compound eyes.

The fruit fly Drosophila melanogaster has two types of external visual organs, a pair of compound eyes and a group of three ocelli. At the time of neurogenesis, the proneural transcription factor Atonal mediates the transition from progenitor cells to differentiating photoreceptor neurons in both organs. In the developing compound eye, atonal (ato) expression is directly induced by transcriptional regulators that confer retinal identity, the Retinal Determination (RD) factors. Little is known, however, about control of ato transcription in the ocelli. Here we show that a 2kb genomic DNA fragment contains distinct and common regulatory elements necessary for ato induction in compound eyes and ocelli. The three binding sites that mediate direct regulation by the RD factors Sine oculis and Eyeless in the compound eye are also required in the ocelli. However, in the latter, these sites mediate control by Sine oculis and the other Pax6 factor of Drosophila, Twin of eyeless, which can bind the Pax6 sites in vitro. Moreover, the three sites are differentially utilized in the ocelli: all three are similarly essential for atonal induction in the posterior ocelli, but show considerable redundancy in the anterior ocellus. Strikingly, this difference parallels the distinct control of ato transcription in the posterior and anterior progenitors of the developing compound eyes. From a comparative perspective, our findings suggest that the ocelli of arthropods may have originated through spatial partitioning from the dorsal edge of an ancestral compound eye.

Mitf is a master regulator of the v-ATPase, forming a control module for cellular homeostasis with v-ATPase and TORC1.

The v-ATPase is a fundamental eukaryotic enzyme that is central to cellular homeostasis. Although its impact on key metabolic regulators such as TORC1 is well documented, our knowledge of mechanisms that regulate v-ATPase activity is limited. Here, we report that the Drosophila transcription factor Mitf is a master regulator of this holoenzyme. Mitf directly controls transcription of all 15 v-ATPase components through M-box cis-sites and this coordinated regulation affects holoenzyme activity in vivo. In addition, through the v-ATPase, Mitf promotes the activity of TORC1, which in turn negatively regulates Mitf. We provide evidence that Mitf, v-ATPase and TORC1 form a negative regulatory loop that maintains each of these important metabolic regulators in relative balance. Interestingly, direct regulation of v-ATPase genes by human MITF also occurs in cells of the melanocytic lineage, showing mechanistic conservation in the regulation of the v-ATPase by MITF family proteins in fly and mammals. Collectively, this evidence points to an ancient module comprising Mitf, v-ATPase and TORC1 that serves as a dynamic modulator of metabolism for cellular homeostasis.

A General Strategy Assisted with Dual Reductants and Dual Protecting Agents for Preparing Pt-Based Alloys with High-Index Facets and Excellent Electrocatalytic Performance.

Synthesizing noble metallic nanoparticles (NPs) enclosed by high-index facets (HIFs) is challenged as it involves the tuning of growth kinetics, the selective adsorption of certain chemical species, and the epitaxial growth from HIF enclosed seeds. Herein, a simple and general strategy is reported by using dual reduction agents and dual capping agents to prepare Pt-based alloy NPs with HIFs, in which both glycine and poly(vinylpyrrolidone) serve as the reductants and capping agents. Due to the facilely tunable growth/nucleation rates and protecting abilities of the reductants and capping agents, Pt concave nanocube (CNC), binary Pt-Ni CNC, ternary Pt-Mn-Cu CNC, and Pt-Mn-Cu ramiform polyhedron alloy NPs terminated by HIFs as well as other NPs with well-defined morphologies such as Pt-Mn-Cu nanocube and Pt-Mn-Cu nanoflower are obtained with this approach. Owing to the high density of low-coordinated Pt sites (HIF structure) and the unique electronic effect of Pt-Mn-Cu ternary alloys, the as-prepared Pt-Mn-Cu NPs show enhanced catalytic activity toward methanol and formic acid electro-oxidation reactions with excellent stability. This work provides a promising methodology for designing and fabricating Pt-based alloy NPs as efficient fuel cell catalyst.

Sensitive determination of typical phenols in environmental water samples by magnetic solid-phase extraction with polyaniline@SiO2 @Fe as the adsorbents before HPLC.

A novel magnetic core-shell material polyaniline@SiO2 @Fe (PANI@SiO2 @Fe) has been successfully synthesized and investigated as an effective adsorbent for the magnetic solid-phase extraction of typical endocrine disrupting compounds such as bisphenol A, tetrabromobisphenol A, and 4-nonylphenol from water samples. The morphology of the as-prepared PANI@SiO2 @Fe was characterized by transmission electron microscopy and X-ray diffraction. The main parameters that influenced the enrichment performance such as the kind of eluent, amount of adsorbent, volume of eluent, adsorption time, elution time, ionic strength, pH, concentration of humic acid, and sample volume were investigated. Under the optimal conditions, a good linear relationship was found in the range of 0.05-100 µg/L for bisphenol A, 0.05-300 µg/L for tetrabromobisphenol A, and 0.05-250 µg/L for 4-nonylphenol, respectively. The correlation coefficients are all above 0.995. The limits of detection were in the range of 0.009-0.04 µg/L, and precisions were under 3.73% (n = 6). The real water analysis indicated that the spiked recoveries were in the range of 92.9-98.9% (n = 3). All these results indicated that the developed method was an efficient tool for the analysis of bisphenol A, tetrabromobisphenol A, and 4-nonylphenol.

Recyclable nanoscale zero-valent iron-based magnetic polydopamine coated nanomaterials for the adsorption and removal of phenanthrene and anthracene.

In this study, nanoscale zero-valent iron nanoparticles (NZVIs) were coated with silica and polydopamine using a two-step process. The coated nanoparticles were applied as adsorbents for removal of two common polycyclic aromatic hydrocarbons pollutants, phenanthrene (PHE) and anthracene (ANT) from aqueous system. Adsorption kinetics followed a pseudo-second-order model. Isotherms and thermodynamics were investigated and the results indicated that the adsorption process fit best to the Freundlich model and exhibited the characteristics of an exothermal physical adsorption process. Owing to their superparamagnetic characteristics and stability, these adsorbents could be easily collected and recycled for reuse.

Mutant analysis by rescue gene excision: New tools for mosaic studies in Drosophila.

A host of classical and molecular genetic tools make Drosophila a tremendous model for the dissection of gene activity. In particular, the FLP-FRT technique for mitotic recombination has greatly enhanced gene loss-of-function analysis. This technique efficiently induces formation of homozygous mutant clones in tissues of heterozygous organisms. However, the dependence of the FLP-FRT method on cell division, and other constraints, also impose limits on its effectiveness. We describe here the generation and testing of tools for Mutant Analysis by Rescue Gene Excision (MARGE), an approach whereby mutant cells are formed by loss of a rescue transgene in a homozygous mutant organism. Rescue-transgene loss can be induced in any tissue or cell-type and at any time during development or in the adult using available heat-shock-induced or tissue-specific flippases, or combinations of UAS-FLP with Gal4 and Gal80ts reagents. The simultaneous loss of a constitutive fluorescence marker (GFP or RFP) identifies the mutant cells. We demonstrate the efficacy of the MARGE technique by flip-out (clonal and disc-wide) of a Ubi-GFP-carrying construct in imaginal discs, and by inducing a known yki mutant phenotype in the Drosophila ovary.

Determination of phthalate esters at trace level from environmental water samples by magnetic solid-phase extraction with Fe@SiO2@polyethyleneimine magnetic nanoparticles as adsorbent prior to high-performance liquid chromatography.

In this work, polyethyleneimine grafted silica-coated nanoscale zero valent iron (Fe@SiO2@PEI) has been successfully synthesized and was investigated to be an effective adsorbent for efficient enrichment of five phthalate esters such as diphenyl phthalate, dibenzyl phthalate, butyl benzyl phthalate, diphenyl isophthalate, and dicyclohexyl phthalate (DPP, DBP, BBP, DPIP, and DCHP) from environmental water samples. The structure and morphology of the materials were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction(XRD). The parameters that influenced the enrichment performance such as amount of sorbent, sample pH, type of eluent, volume of eluent, salting-out effect, adsorption time, and desorption time were investigated. Under optimal conditions, excellent linear relationships were found in the concentration range from 0.5 to 100 µg L(-1), the limits of detection (S/N = 3) were in the range of 0.26-0.45 µg L(-1), and the intra-day and inter-day precisions (n = 6) were in the range of 3.7-4.8 and 3.2-4.3 %, respectively. The developed method was evaluated with real water samples, and satisfied spiked recoveries in the range of 99-104 % were achieved. The experimental results proved that Fe@SiO2@PEI had good adsorption for phthalate esters, and would be a good adsorbent for the magnetic solid-phase extraction of important pollutants from environmental water samples.ᅟ Graphical abstract A flowchart of the synthesis of polyethyleneimine grafted silica coated nanoscale zero valent iron (Fe@SiO2@PEI) and the process of the developed magnetic solid phase extraction of phthalate esters before the analysis by high performance liquid chromatography.

ato-Gal4 fly lines for gene function analysis: Eya is required in late progenitors for eye morphogenesis.

The Gal4/UAS system is one of the most powerful tools for the study of cellular and developmental processes in Drosophila. Gal4 drivers can be used to induce targeted expression of dominant-negative and dominant-active proteins, histological markers, activity sensors, gene-specific dsRNAs, modulators of cell survival or proliferation, and other reagents. Here, we describe novel atonal-Gal4 lines that contain regions of the regulatory DNA of atonal, the proneural gene for photoreceptors, stretch receptors, auditory organ, and some olfactory sensilla. During neurogenesis, the atonal gene is expressed at a critical juncture, a time of transition from progenitor cell to developing neuron. Thus, these lines are particularly well suited for the study of the transcription factors and signaling molecules orchestrating this critical transition. To demonstrate their usefulness, we focus on two visual organs, the eye and the Bolwig. We demonstrate the induction of predicted eye phenotypes when expressing the dominant-negative EGF receptor or a dsRNA against Notch in the developing eye disc. In another example, we show the deletion of the Bolwig's organ using the proapoptotic factor Hid. Finally, we investigate the function of the eye specification factor Eyes absent or Eya in late retinal progenitors, shortly before they begin morphogenesis. We show that Eya is still required in these late progenitors to promote eye formation, and show failure to induce the target gene atonal and consequent lack of neuron formation.

Onset of atonal expression in Drosophila retinal progenitors involves redundant and synergistic contributions of Ey/Pax6 and So binding sites within two distant enhancers.

Proneural transcription factors drive the generation of specialized neurons during nervous system development, and their dynamic expression pattern is critical to their function. The activation of the proneural gene atonal (ato) in the Drosophila eye disc epithelium represents a critical step in the transition from retinal progenitor cell to developing photoreceptor neuron. We show here that the onset of ato transcription depends on two distant enhancers that function differently in subsets of retinal progenitor cells. A detailed analysis of the crosstalk between these enhancers identifies a critical role for three binding sites for the Retinal Determination factors Eyeless (Ey) and Sine oculis (So). We show how these sites interact to induce ato expression in distinct regions of the eye field and confirm them to be occupied by endogenous Ey and So proteins in vivo. Our study suggests that Ey and So operate differently through the same 3' cis-regulatory sites in distinct populations of retinal progenitors.