This article is focused on Netrin1
factor and how it affects growth of axons in the embryonic spinal cords of
mice. Netrin1 is found in both the floor plate of the spinal cord and in neural
progenitors in the ventricular zone. This study aims to discover the source of
netrin1 responsible for guiding axon growth. They picked different areas of the
spinal cord and removed netrin from those areas. Used a control group, a Gli2
(key transcriptional regulator that transduces sonic hedgehog signaling) mutant
group and a Gli2 and netrin1 double mutant in the floorplate  and found that axon defects in netrin1
mutants don’t come from a loss of netrin1 in the floorplate. Next wanted to see
if removing netrin1 in the ventricular zone would have the same effect on axon
guidance. Their experiments showed that the axonal growth defects seen in the
mutants were due to the loss of netrin1 in the ventricular zone and not the
floor plate. Concluded that netrin1 derived from the ventricular zone works
with laminin to act as a growth factor for the axons.

I thought the experimenters did a
pretty thorough job in determining whether the ventricular zone or the floor
plate was the source of the netrin1. They first tested its absence in the floor
plate and then the absence in the ventricular zone. I would maybe try and find
a way to make sure these experiments are replicable and maybe elaborate on the
use of ECM factors such as laminin and collagen and its effects on axon
extension talked about on page 9 of the article.