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Extracellular Engrailed participates in the topographic guidance of retinal axons in vivo.

ABSTRACT: Engrailed transcription factors regulate the expression of guidance cues that pattern retinal axon terminals in the dorsal midbrain. They also act directly to guide axon growth in vitro. We show here that an extracellular En gradient exists in the tectum along the anterior-posterior axis. Neutralizing extracellular Engrailed in vivo with antibodies expressed in the tectum causes temporal axons to map aberrantly to the posterior tectum in chick and Xenopus. Furthermore, posterior membranes from wild-type tecta incubated with anti-Engrailed antibodies or posterior membranes from Engrailed-1 knockout mice exhibit diminished repulsive activity for temporal axons. Since EphrinAs play a major role in anterior-posterior mapping, we tested whether Engrailed cooperates with EphrinA5 in vitro. We find that Engrailed restores full repulsion to axons given subthreshold doses of EphrinA5. Collectively, our results indicate that extracellular Engrailed contributes to retinotectal mapping in vivo by modulating the sensitivity of growth cones to EphrinA.

SUBMITTER: Wizenmann A

PROVIDER: S-EPMC4603356 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature

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Extracellular Engrailed participates in the topographic guidance of retinal axons in vivo.

Wizenmann Andrea A Brunet Isabelle I Lam Joyce J Sonnier Laure L Beurdeley Marine M Zarbalis Konstantinos K Weisenhorn-Vogt Daniela D Weinl Christine C Dwivedy Asha A Joliot Alain A Wurst Wolfgang W Holt Christine C Prochiantz Alain A

Neuron 20091101 3

Engrailed transcription factors regulate the expression of guidance cues that pattern retinal axon terminals in the dorsal midbrain. They also act directly to guide axon growth in vitro. We show here that an extracellular En gradient exists in the tectum along the anterior-posterior axis. Neutralizing extracellular Engrailed in vivo with antibodies expressed in the tectum causes temporal axons to map aberrantly to the posterior tectum in chick and Xenopus. Furthermore, posterior membranes from w ...[more]

PMID: 19914184

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Project description:Introduction: To date, tubular tissue engineering relies on large, non-porous tubular scaffolds (Ø > 2 mm) for mechanical self-support, or smaller (Ø 150-500 μm) tubes within bulk hydrogels for studying renal transport phenomena. To advance the engineering of kidney tubules for future implantation, constructs should be both self-supportive and yet small-sized and highly porous. Here, we hypothesize that the fabrication of small-sized porous tubular scaffolds with a highly organized fibrous microstructure by means of melt-electrowriting (MEW) allows the development of self-supported kidney proximal tubules with enhanced properties. Materials and Methods: A custom-built melt-electrowriting (MEW) device was used to fabricate tubular fibrous scaffolds with small diameter sizes (Ø = 0.5, 1, 3 mm) and well-defined, porous microarchitectures (rhombus, square, and random). Human umbilical vein endothelial cells (HUVEC) and human conditionally immortalized proximal tubular epithelial cells (ciPTEC) were seeded into the tubular scaffolds and tested for monolayer formation, integrity, and organization, as well as for extracellular matrix (ECM) production and renal transport functionality. Results: Tubular fibrous scaffolds were successfully manufactured by fine control of MEW instrument parameters. A minimum inner diameter of 1 mm and pore sizes of 0.2 mm were achieved and used for subsequent cell experiments. While HUVEC were unable to bridge the pores, ciPTEC formed tight monolayers in all scaffold microarchitectures tested. Well-defined rhombus-shaped pores outperformed and facilitated unidirectional cell orientation, increased collagen type IV deposition, and expression of the renal transporters and differentiation markers organic cation transporter 2 (OCT2) and P-glycoprotein (P-gp). Discussion and Conclusion: Here, we present smaller diameter engineered kidney tubules with microgeometry-directed cell functionality. Due to the well-organized tubular fiber scaffold microstructure, the tubes are mechanically self-supported, and the self-produced ECM constitutes the only barrier between the inner and outer compartment, facilitating rapid and active solute transport.

Dataset Information

Extracellular Engrailed participates in the topographic guidance of retinal axons in vivo.

Publications

Extracellular Engrailed participates in the topographic guidance of retinal axons in vivo.

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