axon regeneration as part of differentiation?

[Nicolas Le Novère]

>> I wanted to see if anyone else in the Neuro interest group thought
>> there was an issue here before I posted a SF tracker item on it.
>> The term GO:0031103 'axon regeneration' has 'neuron morphogenesis
>> during differentiation' in it's path to root. This means that the
>> process of 'axon regeneration' in GO is implicitly restricted to
>> occur during neuron differentiation.   This doesn't seem correct to
>> me.  It seems to me that 'axon regeneration' is the extenstion of
>> an axon by a mature neuron (ie not a differentiating neuron) after
>> loss of the axon for some reason.
>
> Depends on what happens at the molecular level, which I am interested
> to find out if we know one way or the other. Does regeneration
> involve the same process, albeit locally within the axon, that would
> be occurring during the original differentiation?

Even if the molecular processes are different (and they're not) it is
still axon regeneration, so the concern is sound.

> Somehow I remember
> way back when reading that in some peripheral cases schwann cells act
> as a guide, but there is no guarantee that the axon will return to
> its previous precise location, and that the growing axon repeats the
> process that occurred in differentiation, though now, because of
> physical constraints it has a limited number of choices.

Yep, and since the growth factors and ephrin gradients are not there, the
guidance would be different. But the axonal bit is the same.

>> This process doesn't involve de-differentiation and re-
>> differentiation of the neuron.
>
> Isn't the fact that it is an extending axon, a form of "de-
> differentiation? Differentiated axons don't extend?

No, no. Differentiated axons extend. They grow collaterals. It is one of
the form of long-term plasticity.


-- 
Nicolas LE NOVÈRE,  Computational Neurobiology,
EMBL-EBI, Wellcome-Trust Genome Campus, Hinxton, Cambridge, CB10 1SD, UK
Tel: +44(0)1223 494 521,  Fax: +44(0)1223 494 468,  Mob: +33(0)689218676
http://www.ebi.ac.uk/~lenov