UNC-5
The vertebrate orthologue of UNC-6, netrin-1 was determined to be a key guidance cue for axons moving toward the ventral midline in the rodent embryo spinal cord.
Netrin-1 has been identified as a critical component of embryonic development with functions in axon guidance, cell migration, morphogenesis and angiogenesis.
When filled with dye, the processes and cell bodies of these neurons can be examined in live animals by fluorescence microscopy.
[2] There are three phases in hermaphrodite distal tip cell migration in Caenorhabditis elegans which are distinguished by the orientation of their movements which alternate between anteroposterior and dorsoventral axes.
Experimentation has shown that UNC-5 is coincident with the second migration phase and that premature expression will result in turning in a UNC-6 dependent manner.
This is relevant because is shows that the mislocalization defect is due to a change in temperature at the L4 larval stage which occurs after DA9 is fully developed.
[1] When testing directly for whether UNC-6 netrin provides information for localization of presynaptic components an interesting discovery was made.
They further observed that the enlarged asynaptic domain is restored partly in UNC-5 which demonstrates that UNC-5 acts cell autonomously in DA9 in order to mediate ectopic UNC-6 exclusion of presynaptic components.
UNC-6 was recently found to cause the initial polarization of the C. elegans hermaphrodite specific neuronal cell body.
The results of these findings suggest that UNC-5 homologues make up a primary method of netrin-1 signal transduction in the adult spinal cord.
[citation needed] Similar to growth cone guidance, synapse formation is cued by UNC-5 through a UNC-6 gradient that repels the dorsal axon migration.
UNC-129 mediates expression of dorsoventral polarity information required for axon guidance and guided cell migrations in Caenorhabditis elegans.
[11] Recently it was found that dendrites do not overlap and actively avoid each other because cell specific membrane proteins trigger mutual repulsion.
[citation needed] Netrins share the same terminal structure with vertebrate laminins but appear minimally related.
Netrins are involved in heterotropic LN domain interactions during this process which suggests that although similar in structure, the functions of the two families are different.
During the last 15 years, controversial data has failed to firmly establish whether DCC is indeed a tumour suppressor gene.
These data suggests that netrin-1 could be an endogenous trophic factor for Schwann cells in the injured peripheral nerves.
