Journal of Neuroscience, Vol 7, 2651-2663, Copyright © 1987 by Society for Neuroscience
Temporal and topographic relationships between the phosphorylated and nonphosphorylated epitopes of the 200 kDa neurofilament protein during development in vitro
GA Foster, D Dahl and VM Lee
The ontogeny of the triplet of neurofilament proteins (NF), and the
phosphorylated and nonphosphorylated derivatives of the 200 kDa
neurofilament subunit (NF200P, NF200D) have been investigated in
dissociated cultures prepared from gestational day 13 mouse spinal cord and
dorsal root ganglia (DRG), using immunocytochemical methods.
Neurofilament-like immunoreactivity (NF-LI), as detected with antiserum,
occurred in the somata and processes of all neurons from day 1 in culture,
and reached a maximum density and intensity at days 16- 20. The first
labeling of neurons by NF200D antibodies occurred at day 3, and was
confined to DRG cells. Only a small, proximal portion of the axons from
these cells exhibited NF200D-LI. At later stages, however, this
immunoreactive region extended to include progressively more distal parts.
Spinal cord neurons first became NF200D-positive at day 9; however, many
NF200D-negative neurons still remained in mature cultures. Also at these
later stages, some axons were stained for less than their full length with
the NF200D antibody. NF200P-LI was first apparent at day 17, in smooth and
varicose axons and only where NF-LI was also present. In contrast, NF200P-
and NF200D-LI were usually localized in mutually exclusive populations of
axons and other fibers. In some, predominantly thick axons, however, the
proximal segment was NF200D-positive, whereas the distal part exhibited
solely NF200P-LI. In contrast to NF70 and NF150, the 200 kDa neurofilament
is dilatory in its appearance in most neurons in culture. The development
of the nonphosphoderivative precedes that of the phosphoderivative, and the
respective ontogenies are specific for different neuronal types.
Posttranslational phosphorylation of NF200 seems therefore to occur at a
later stage of development than the induction of NF200 itself, while there
is a wide variation in its rates of phosphorylation during passage down
different axons.