Above: Growth cone of retinal ganglion cell axon showing asymmetrical distribution of beta-actin after exposure to a 5 minute gradient of netrin-1 (top right). This spatial  asymmetry is generated by local translation of beta-actin mRNA and is critical for attractive turning towards netrin-1 (see Leung et al, 2006).

Above: Single retinal ganglion cell in the embryonic visual system. The cell is stained with a dye (HRP) to reveal its soma and developing dendrites in the eye and its long axon extending across the midline (optic chiasm) into the contralateral optic tract. It is tipped with a motile growth process, the growth cone, which responds to guidance cues along the pathway and leads the axon to its final destination in the midbrain.

Quicktime Movie: in vivo Timelapse Imaging of Retinotectal Axon Pathfinding in Xenopus laevis

• Small version (1.92MB)
• Large version (4.94MB)

We are investigating how axons are guided to their correct synaptic targets in the brain. In the developing vertebrate visual system, retinal ganglion cells in the eye extend axons that navigate over a long distance to their synaptic targets in the midbrain. This impressive navigational feat underlies the precise wiring of the mature brain and is essential for building functional nerve connections. The goal of our research is to understand the molecular and cellular mechanisms that guide axon growth. We use a multidisciplinary experimental approach that involves in vivo gene transfer, growth cone turning assays in vitro and time-lapse imaging of live axons in the brain. We focus in particular on the steering points within the visual pathway where axons alter their direction of growth and/or their behaviour such as the optic disc, the optic chiasm and the site of target entry. We have found, for example, that ephrin-B is important in regulating the divergent routing of axons at the chiasm and that netrin-1/DCC/laminin-1 interactions play a key role in directing axons out of the eye. Our studies have also revealed that the growing tips of axons, the growth cones, rapidly synthesize new proteins in response to encounters with guidance cues such as netrin-1. Inhibition of this local protein synthesis blocks the turning responses of growth cones in a chemotropic gradient suggesting that local translation of mRNAs is involved in directional steering. By understanding the molecular and cellular mechanisms that guide axon growth in development we aim to understand how nerve connections are first established. Basic knowledge of this sort is essential for the development of clinical therapies in nerve repair.

A short movie depicting in vivo Time-lapse Imaging of Retinotectal Axon Pathfinding in Xenopus laevis can be viewed here.

PhD student applications are welcome for Oct 2009 and should be received by Jan-Feb 2009.

Colleagues:

Joyce Lam (PhD Student)
Louis Leung (PhD Student)
Hanno Svoboda (PhD Student)
Jason (Byung) Yoon (PhD Student)
Jimmy Stake (MPhil Student)
Kimmy Leung (Postdoctoral Fellow)
Francis van Horck (Postdoctoral Fellow)
Julien Falk (Postdoctoral Fellow)
Krishna Zivraj (Postdoctoral Fellow)
Marie-Laure Baudet (Postdoctoral Fellow)
Asha Dwivedy (Research Associate)
Thomasz Dyl (Research Technician)
Adrian McNabb (Research Technician)

Main Collaborators:

Bill Harris (PDN, Cambridge University)
Alain Prochiantz (CNRS, Paris)
James Fawcett (Brain Repair Centre, Cambridge)
Giles Yeo (Addenbrooke’s Hospital, Cambridge University)

Main sources of funding: Wellcome Trust, MRC.

Selected publications

Strochlic L, Dwivedy A, van Horck FP, Falk J, Holt CE.   A role for S1P signalling in axon guidance in the Xenopus visual system. Development 135(2):333-42. (2008).

Dwivedy, A., F.B. Gertler, J. Miller, C.E. Holt, and C. Lebrand. Critical Role of Ena/VASP Proteins for Retinal Axon Growth Cone Dynamics and Branching in Xenopus Embryo.  Development 134(11):2137-46 (2007).

Lin AC and CE Holt. Local translation and directional steering in axons. MiniReview. EMBO J. Aug 22;26(16):3729-36.

Leung, K-M., van Horck, FPG, Andrew C Lin, Allison, R., Standart, N. and Holt, CE. Asymmetrical b-actin mRNA translation in growth cones mediates attractive turning to netrin-1. Nature Neuroscience Oct;9(10):1247-56 (2006).

Piper. M., R. Anderson, A. Dwivedy, C. Weinl, F. van Horck, K-M. Leung, E. Cogill and C. Holt Signaling mechanisms underlying Slit2-induced collapse of Xenopus retinal growth cones. Neuron 49: 215-228 (2006).

Brunet I., C. Weinl, M. Piper, A. Trembleau, M. Volovitch, W.A. Harris, A. Prochiantz, C.E. Holt. The transcription factor Engrailed-2 guides retinal axons. Nature 438: 94-98 (2005).

Piper, M., S. Salih, C. Weinl, C.E. Holt and W. A. Harris. Endocytosis-dependent desensitization and protein synthesis-dependent resensitization in retinal growth cone adaptation. Nature Neuroscience 8: 179-186. Advance Online publication, 9 Jan. (2005).

Piper, M. and C.E. Holt. RNA Translation in Axons. Annual Review of Cell and Developmental Biology 20: 505-23 (2004).

van Horck, F.P.G., Weinl, C. and C.E. Holt. Retinal axon guidance: novel mechanisms for steering. Current Opinion in Neurobiology (2004) 14:61-66.

Campbell. D.S. and C.E. Holt Apoptotic pathway and MAPKs differentially regulate chemotropic responses in retinal growth cones. Neuron 37: 939-952 (2003).

Shewan, D.S., A. Dwivedy, R. Anderson and C.E. Holt. Age-related changes underlie switch in netrin-1 responsiveness as growth cones advance along visual pathway. Nature Neuroscience 5: 955-962 (2002).

Mann F, Ray, S., Harris, W.A. and Holt, C.E. Topographic mapping in dorsoventral axis of the Xenopus retinotectal system depends on signalling through ephrin-B ligands. Neuron 35:461-473 (2002).

Campbell, D.S. and C.E. Holt. Chemotropic responses of retinal growth cones mediated by rapid local protein synthesis and degradation. Neuron 32: 1013-1026 (2001).

Nakagawa, S-i., C. Brennan, K. Johnson, D. Shewan, W.A. Harris and C.E. Holt. Ephrin-B regulates the ipsilateral routing of retinal axons at the optic chiasm. Neuron 25: 599-610 (2000).