BDNF promotes target innervation of Xenopus mandibular trigeminal axons in vivo

Huang, J.K. Dorey, K. Ishibashi, S. & Amaya, E.

BMC Developmental Biology 7:59 (2007)

ABSTRACT: Trigeminal nerves consist of ophthalmic, maxillary, and mandibular branches that project to distinct regions of the facial epidermis. In Xenopus embryos, the mandibular branch of the trigeminal nerve extends toward and innervates the cement gland in the anterior facial epithelium. The cement gland has previously been proposed to provide a short-range chemoattractive signal to promote target innervation by mandibular trigeminal axons. Brain derived neurotrophic factor, BDNF is known to stimulate axon outgrowth and branching. The goal of this study is to determine whether BDNF functions as the proposed target recognition signal in the Xenopus cement gland.
We found that the cement gland is enriched in BDNF mRNA transcripts compared to the other neurotrophins NT3 and NT4 during mandibular trigeminal nerve innervation. BDNF knockdown in Xenopus embryos or specifically in cement glands resulted in the failure of mandibular trigeminal axons to arborise or grow into the cement gland. BDNF expressed ectodermal grafts, when positioned in place of the cement gland, promoted local trigeminal axon arborisation in vivo...

© 2007 BioMed Central Ltd

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Figure 5: Trigeminal nerve in a transgenic stage 28 tadpole
Figure 6: Cranial nerves revealed in a transgenic stage 47 tadpole