Could anyone give me some ideas that what neurons are wired at later time during development? Thanks!
what are the neurons that are wired later during development?
you’ll get an overview by looking in the hermaphrodite handbook;
also in the descriptions and from the lineages of individual neurones in the worm atlas;
or are you after something more specific?
Any neurons which are born postembryonically will be wired later in development.
The ones that I know off the top of my head are the VNC MNs VA, VB, VC, VD, AS and the proprioceptor PVD.
The links that Steve listed should help you identify the other postembryonic neurons.
Thank you so much! Two Steves!
I am looking for some neurons that could be wired at the late-L4 stage.
For that time period, the most likely new wiring will be related to sex-specific behaviors. We know for sure that many male-related neurons and sex muscles are not ready to attain their wiring until late L4 stages. In the male, some shared neurons (the “core” nervous system) also change their wiring at this time to allow new roles during adulthood. Even a few core muscles in the tail change positions and re-wire.
But I am guessing that you were thinking about the hermaphrodite. We have no data to answer that query, since we know rather little so far about the L4 wiring in hermaphrodite. But by analogy to the male, we can predict that the wiring of VCs and HSN will likely become much stronger to the vulval muscles, especially, but perhaps they alter other wiring too. These neurons might even lose connectivity that prevailed before the vulval muscles become available as targets.
The hermaphrodite is not known to be very responsive to sexual cues in the manner that males are. If such behavior were to exist, it’s wiring in the nerve ring might develop quite late - maybe outputs from chemosensors (for pheromones) would be changing. But that goes to wild speculation.
Thanks so much for the input, Hall!
This brings my another question: Whether or not all neuronal wirings are completed during developmental stage? any papers addressed this question? Thanks!
The Emmons lab (and perhaps others) have shown in the young male that its behavior is still changing for hours after the last molt, which must reflect continued changes in its wiring during young adulthood. Based upon TEM data that we’ve received from John Sulston (work done at the MRC) for several male tails that were sectioned at different ages near this last molt, and for one “old” adult, it appears that neurons in the PAG gain more branches and more synapses, becoming more complex during adulthood (Sulston et al, 1980). By contrast, the hermaphrodite nerve ring is not much different in an L4 (animal “JSH”) and an adult (animal N2U) - these data come from animals produced by John White, Nichol Thomson and others at the MRC (White et al., 1986).
Again, the major wiring changes in adulthood might be concentrated in sex-specific neurons and synapses. But more studies are warranted to compare animals at well defined ages.