1. First Author Forum Rho GTPases: halfway island from gene to circuit Xiao-bing Yuan Neural Plasticity Group Institute of Neuroscience Shanghai Institutes of Biological Sciences Chinese Academy of Science

2. Key steps in the development of neural network Neurogenesis Neuronal migration Axon pathfinding Synapse formation

3. Cajal’s drawing “This fiber ends … in an enlargement which may be rounded and subtle, but that may also adopt a conical appearance. This latter we shall name the growth cone, that at times displays fine and short extensions…” Growth cone “appears to insinuate themselves between the surrounding elements, relentlessly forging a path through the interstitial matrix.” It “endowed with amoeboid movements. It could be compared to a living battering ram, soft and flexible, which advances, pushing aside mechanically the obstacles which it finds in its way, until it reaches the area of its peripheral distribution.” Guide Post First Author Forum

4. Netrins Shh NTs Netrins Semaphorins Slits First Author Forum

5. Cajal’s drawing “This fiber ends … in an enlargement which may be rounded and subtle, but that may also adopt a conical appearance. This latter we shall name the growth cone, that at times displays fine and short extensions…” Growth cone “appears to insinuate themselves between the surrounding elements, relentlessly forging a path through the interstitial matrix.” It “endowed with amoeboid movements. It could be compared to a living battering ram, soft and flexible, which advances, pushing aside mechanically the obstacles which it finds in its way, until it reaches the area of its peripheral distribution.”

6. First Author Forum Receptor Cytoskeleton ?

7. First Author Forum Rho GTPases

8. First Author Forum Rho GTPases

9. First Author Forum Genetic evidences GEFs GAPs Cdc42 Rac RhoA VASP Pak ROCK LOF GOF Axon pathfinding errors

10. First Author Forum Cdc42/Rac1/ RhoA

11. First Author Forum Instructive or permissive ? How ?

12. Models for Rho GTPase functions in growth cone guidance. First Author Forum

13. Conclusions: 1 Rho GTPases mediator 2 cAMP switch 3 crosstalk through myosin

14. This is a fairly comprehensive study of Rho GTPase involvement in axonal turning in the Xenopus spinal cord. (Guan & Rao Nature Review Neuroscience, 2003) First Author Forum

15. BDNF ——› Ca 2+ ——› Cdc42 ——› Attraction ? LPA ——› G  12/13 ——› RhoA ——› Repulsion ? Hypothesis First Author Forum Mediator

16. The Housekeeping Technique Growth cone turning assay ( Poo assay )

17. Select cells with GFP fluorescence 14 - 20 hr rt Turning Assay two-cell stage Fertilized egg Stage 22 dissociation Materials and methods First Author Forum cDNA

18. Materials and methods First Author Forum

19. Results First Author Forum

23. -15 -5 -10 0 0 5 5 10 15 20 25 30 ··············································································· -15 -5 -10 0 0 5 5 10 15 20 25 30 ··············································································· ·················································································································· LPA Y-27632 Figure 5. RhoA- and ROCK-dependent neurite inhibition or collapse induced by LPA. Results First Author Forum

24. ……………………………………..… LPA Results First Author Forum

26. First Author Forum

27. 2001/5/13 Submission to Cell

28. Results First Author Forum

29. First Author Forum

31. 2001/12/06 Resubmission to Cell

32. First Author Forum

33. 2002/4/30 Submission to Neuron

34. First Author Forum 2002/6/24 Submission to NCB

35. First Author Forum

37. 2002/10/22 Resubmission to NCB

38. First Author Forum Conclusions: 1 Instructive role 2 cAMP switch 3 crosstalk through myosin

39. First Author Forum Implications: 1 Axon guidance signaling 2 Nerve regeneration 3 Synapse plasticity

40. Things should be made as simple as possible, but not any simpler Albert Einstein First Author Forum Lessons: comprehensive

41. First Author Forum Lessons:

42. First Author Forum Lessons:

43. First Author Forum Lessons:

44. First Author Forum Lessons:

45. First Author Forum Lessons: Don’t make a comprehensive story. Don’t evade the most important experiment.

46. First Author Forum Questions remain to be clarified: 1 Signaling pathway for growth cone turning 2 Who guides the expression of guidance cues?

47. Acknowledgement Prof. Mu-Ming Poo Dr. Yu- Qinag Ding Prof. Shumin Duan Dr. Yi-Zheng Wang Prof. Chienping Wu Dr. Xue-Liang Zhu Dr. Guo-Li Ming Dr. Gang Pei Dr. Lin-Ying Feng Ming Jin Xiao-Hua Xu Rotation students Thanks ! First Author Forum