7 research outputs found
Restricted growth of Schwann cells lacking Cajal bands slows conduction in myelinated nerves
Nerve impulses are propagated at nodes of Ranvier in the
myelinated nerves of vertebrates. Internodal distances have
been proposed to affect the velocity of nerve impulse conduction;
however, direct evidence is lacking, and the cellular mechanisms
that might regulate the length of the myelinated segments
are unknown. Ramon y Cajal described longitudinal and transverse
bands of cytoplasm or trabeculae in internodal Schwann
cells and suggested that they had a nutritive function. Here we
show that internodal growth in wild-type nerves is precisely
matched to nerve extension, but disruption of the cytoplasmic
bands in Periaxin-null mice impairs Schwann cell elongation during nerve growth. By contrast, myelination proceeds normally.
The capacity of wild-type and mutant Schwann cells to
elongate is cell-autonomous, indicating that passive stretching
can account for the lengthening of the internode during limb
growth. As predicted on theoretical grounds, decreased internodal
distances strikingly decrease conduction velocities and so
affect motor function.We propose that microtubule-based transport
in the longitudinal bands of Cajal permits internodal
Schwann cells to lengthen in response to axonal growth, thus
ensuring rapid nerve impulse transmission