In zebrafish, Müller glia (MG) are a source of retinal stem cells that can replenish damaged retinal neurons and restore vision. In mammals, however, MG do not spontaneously re-enter the cell cycle to generate a population of stem or progenitor cells that differentiate into retinal neurons. Nevertheless, the regenerative machinery may exist in the mammalian retina, as retinal injury can stimulate MG proliferation followed by limited neurogenesis. Therefore, there is still a fundamental question regarding whether MG-derived regeneration can be exploited to restore vision in mammalian retinas. Gene transfer of β-catenin stimulates MG proliferation in the absence of injury in mouse retinas. Here we report that following gene transfer of β-catenin, cell-cycle-reactivated MG can be reprogrammed to generate rod photoreceptors by subsequent gene transfer of transcription factors essential for rod cell fate specification and determination. MG-derived rods restored visual responses in Gnat1Gnat2 double mutant mice, a model of congenital blindness, throughout the visual pathway from the retina to the primary visual cortex. Together, our results provide evidence of vision restoration after de novo MG-derived genesis of rod photoreceptors in mammalian retinas.

In cold-blooded vertebrates such as zebrafish, Müller glial cells (MGs) readily proliferate to replenish lost retinal neurons. In mammals, however, MGs lack regenerative capability as they do not spontaneously re-enter the cell cycle unless the retina is injured. Here, we show that gene transfer of β-catenin in adult mouse retina activates Wnt signaling and MG proliferation without retinal injury. Upstream of Wnt, deletion of GSK3β stabilizes β-catenin and activates MG proliferation. Downstream of Wnt, β-catenin binds to the Lin28 promoter and activates transcription. Deletion of Lin28 abolishes β-catenin-mediated effects on MG proliferation, and Lin28 gene transfer stimulates MG proliferation. We further demonstrate that let-7 miRNAs are critically involved in Wnt/Lin28-regulated MG proliferation. Intriguingly, a subset of cell cycle reactivated MGs express markers for amacrine cells. Together, these results reveal a key role of Wnt-Lin28-let7 miRNA signaling in regulating proliferation and neurogenic potential of MGs in adult mammalian retina.

Genetic studies have suggested a functional link between cholesterol/sphingolipid metabolism and endocytic membrane traffic. Here we show that perturbing the cholesterol/sphingomyelin balance in the plasma membrane results in the massive formation of clusters of narrow endocytic tubular invaginations positive for N-BAR proteins. These tubules are intensely positive for sphingosine kinase 1 (SPHK1). SPHK1 is also targeted to physiologically occurring early endocytic intermediates, and is highly enriched in nerve terminals, cellular compartments specialized for exo-endocytosis. Membrane recruitment of SPHK1 involves a direct, curvature-sensitive interaction with the lipid bilayer mediated by a hydrophobic patch on the enzyme’s surface. The knockdown of SPHKs results in endocytic recycling defects, and a mutation that disrupts the hydrophobic patch of C. elegans SPHK fails to rescue the neurotransmission defects in loss-of-function mutants of this enzyme. Our studies support a role of sphingosine phosphorylation in endocytic membrane trafficking beyond the established function of sphingosine-1-phosphate in intercellular signaling.

Background and Aims Activated hepatocytes are hypothesized to be a major source of signals that drive cirrhosis, but the biochemical pathways that convert hepatocytes into such a state are unclear. We examined the role of the Hippo pathway transcriptional coactivators Yes‐associated protein (YAP) and transcriptional coactivator with PDZ‐binding motif (TAZ) in hepatocytes to facilitate cell–cell interactions that stimulate liver inflammation and fibrosis. Approach and Results Using a variety of genetic, metabolic, and liver injury models in mice, we manipulated Hippo signaling in hepatocytes and examined its effects in nonparenchymal cells to promote liver inflammation and fibrosis. YAP‐expressing hepatocytes rapidly and potently activate the expression of proteins that promote fibrosis (collagen type I alpha 1 chain, tissue inhibitor of metalloproteinase 1, platelet‐derived growth factor c, transforming growth factor β2) and inflammation (tumor necrosis factor, interleukin 1β). They stimulate expansion of myofibroblasts and immune cells, followed by aggressive liver fibrosis. In contrast, hepatocyte‐specific YAP and YAP/TAZ knockouts exhibit limited myofibroblast expansion, less inflammation, and decreased fibrosis after CCl4 injury despite a similar degree of necrosis as controls. We identified cellular communication network factor 1 (CYR61) as a chemokine that is up‐regulated by hepatocytes during liver injury but is expressed at significantly lower levels in mice with hepatocyte‐specific deletion of YAP or TAZ. Gain‐of‐function and loss‐of‐function experiments with CYR61 in vivo point to it being a key chemokine controlling liver fibrosis and inflammation in the context of YAP/TAZ. There is a direct correlation between levels of YAP/TAZ and CYR61 in liver tissues of patients with high‐grade nonalcoholic steatohepatitis. Conclusions Liver injury in mice and humans increases levels of YAP/TAZ/CYR61 in hepatocytes, thus attracting macrophages to the liver to promote inflammation and fibrosis.

ObjectiveTo investigate the discrepancy between patient-reported symptoms and measured clinical findings and influencing factors in dry eye (DE).SettingA population-based, cross-sectional study was performed in July–August 2007 in northeast China. The study was performed on populations originating from two rural districts that are respectively located approximately 377 and 177 km from our hospital.Participants2600 eligible residents from 1300 households were identified; valid responses were obtained from 2262 residents (mean age 48 (range 12–88) years; 926 men and 1336 women; response rate 87%).Primary outcome measuresPatient-reported symptoms of DE, tear film break up time (BUT) and Schirmer scores (Schirmer II).ResultsSubjects with normal BUT and Schirmer scores without any DE symptoms were defined as the control group. Those with abnormal BUT and Schirmer scores and symptoms of DE were defined as the DE group. Subjects with disparities between the occurrence of DE symptoms and measured clinical findings were regarded as the discrepancy. Out of 2262 subjects, the discrepant group contained 960 subjects (42.44%) with significant difference (χ2=4.027, p=0.045<0.05). Factors that influenced the subjective reporting of DE symptoms included gender, smoking status, environment and age. Schirmer II test and tear film BUT values were remarkably different among control, DE and discrepant groups.ConclusionsDevelopment of DE can be related to many factors. It is of great importance to put forward the preclinical phase concept (patients who are symptomatic for DE and yet show no aqueous deficiency or evaporative signs) and to screen outpatients with DE-inducing features. Future interventions should focus on patients demonstrating a discrepancy between self-reported symptomology and measured clinical findings.