A Novel Pathway of TEF Regulation Mediated by MicroRNA-125b Contributes to the Control of Actin Distribution and Cell Shape in Fibroblasts

BACKGROUND: Thyrotroph embryonic factor (TEF), a member of the PAR bZIP family of transcriptional regulators, has been involved in neurotransmitter homeostasis, amino acid metabolism, and regulation of apoptotic proteins. In spite of its relevance, nothing is known about the regulation of TEF. PRINCIPAL FINDINGS: p53-dependent genotoxic agents have been shown to be much more harmful for PAR bZIP-deficient mice as compared to wild type animals. Here we demonstrate that TEF expression is controlled by p53 through upregulation of microRNA-125b, as determined by both regulating the activity of p53 and transfecting cells with microRNA-125b precursors. We also describe a novel role for TEF in controlling actin distribution and cell shape in mouse fibroblasts. Lack of TEF is accompanied by dramatic increase of cell area and decrease of elongation (bipolarity) and dispersion (multipolarity). Staining of actin cytoskeleton also showed that TEF (-/-) cells are characterized by appearance of circumferential actin bundles and disappearance of straight fibers. Interestingly, transfection of TEF (-/-) fibroblasts with TEF induced a wild type-like phenotype. Consistent with our previous findings, transfection of wild type fibroblasts with miR-125b promoted a TEF (-/-)-like phenotype, and a similar but weaker effect was observed following exogenous expression of p53. CONCLUSIONS/SIGNIFICANCE: These findings provide the first evidence of TEF regulation, through a miR-125b-mediated pathway, and describes a novel role of TEF in the maintenance of cell shape in fibroblasts

Thyrotroph Embryonic Factor Regulates Light-Induced Transcription of Repair Genes in Zebrafish Embryonic Cells

Numerous responses are triggered by light in the cell. How the light signal is detected and transduced into a cellular response is still an enigma. Each zebrafish cell has the capacity to directly detect light, making this organism particularly suitable for the study of light dependent transcription. To gain insight into the light signalling mechanism we identified genes that are activated by light exposure at an early embryonic stage, when specialised light sensing organs have not yet formed. We screened over 14,900 genes using micro-array GeneChips, and identified 19 light-induced genes that function primarily in light signalling, stress response, and DNA repair. Here we reveal that PAR Response Elements are present in all promoters of the light-induced genes, and demonstrate a pivotal role for the PAR bZip transcription factor Thyrotroph embryonic factor (Tef) in regulating the majority of light-induced genes. We show that tefβ transcription is directly regulated by light while transcription of tefα is under circadian clock control at later stages of development. These data leads us to propose their involvement in light-induced UV tolerance in the zebrafish embryo

sFlt Multivalent Conjugates Inhibit Angiogenesis and Improve Half-Life In Vivo

We would like to thank Jonathan Winger and Xiao Zhu for guidance with the insect cell protein expression system and providing reagents. We would like to acknowledge Ann Fischer for help with expressing the sFlt protein in the Tissue Culture Facility at UC Berkeley and Dawn Spelke and Anusuya Ramasubramanian for help optimizing protein purification from insect cells. We are also grateful for the help from Leah Byrne and John Flannery at in the Helen Wills Neuroscience Institute at UC Berkeley for aiding us in the development of the rat intravitreal residence time model and for allowing us to use their facilities.Current anti-VEGF drugs for patients with diabetic retinopathy suffer from short residence time in the vitreous of the eye. In order to maintain biologically effective doses of drug for inhibiting retinal neovascularization, patients are required to receive regular monthly injections of drug, which often results in low patient compliance and progression of the disease. To improve the intravitreal residence time of anti-VEGF drugs, we have synthesized multivalent bioconjugates of an anti-VEGF protein, soluble fms-like tyrosine kinase-1 (sFlt) that is covalently grafted to chains of hyaluronic acid (HyA), conjugates that are termed mvsFlt. Using a mouse corneal angiogenesis assay, we demonstrate that covalent conjugation to HyA chains does not decrease the bioactivity of sFlt and that mvsFlt is equivalent to sFlt at inhibiting corneal angiogenesis. In a rat vitreous model, we observed that mvsFlt had significantly increased intravitreal residence time compared to the unconjugated sFlt after 2 days. The calculated intravitreal half-lives for sFlt and mvsFlt were 3.3 and 35 hours, respectively. Furthermore, we show that mvsFlt is more effective than the unconjugated form at inhibiting retinal neovascularization in an oxygen-induced retinopathy model, an effect that is most likely due to the longer half-life of mvsFlt in the vitreous. Taken together, our results indicate that conjugation of sFlt to HyA does not affect its affinity for VEGF and this conjugation significantly improves drug half-life. These in vivo results suggest that our strategy of multivalent conjugation could substantially improve upon drug half-life, and thus the efficacy of currently available drugs that are used in diseases such as diabetic retinopathy, thereby improving patient quality of life.Yeshttp://www.plosone.org/static/editorial#pee