Volume 17, Number 6,
Issue of March 15, 1997
pp. 2056-2070
Copyright ©1997 Society for Neuroscience
Proteolipid Protein Regulates the Survival and
Differentiation of Oligodendrocytes
Received July 1, 1996; revised Dec. 31, 1996; accepted Dec. 31, 1996.
Xiaoyi Yang and
Robert P. Skoff
Department of Anatomy and Cell Biology, Wayne State University
School of Medicine, Detroit, Michigan 48201
Proteolipid protein (PLP) has been postulated to play a critical
role in the early differentiation of oligodendrocytes (OLs) in addition
to its known role as a structural component of myelin. To identify this
early function, we blocked the synthesis of PLP in glial cultures with
antisense oligodeoxynucleotides that targeted the PLP initiation codon.
Primary glial cultures were incubated with phosphorothioate-protected
oligodeoxynucleotides (S-ODNs) for up to 11 d. PLP in OLs was
reduced >90%. OLs treated with antisense S-ODNs appeared strikingly
healthy as judged by (1) immunocytochemical staining for myelin
glycolipids and myelin basic protein, (2) their prolonged survival
compared with untreated cultures, and (3) their ability to re-establish
membrane sheets after removal of the S-ODNs.
Our studies show that PLP is required for elaboration and stability of
the myelin membrane sheets made by most OLs, but it is not necessary
for the network of processes established by OLs. More importantly, the
number of OLs in the antisense-treated cultures was nearly sevenfold
greater after a 10-11 d incubation with S-ODNs than in control
cultures. The number of proliferating OL progenitors was not increased
in the antisense-treated cultures, indicating that the increase in the
number of OLs was attributable to prolonged OL survival. The tissue
culture studies reveal that the absence of PLP/DM20 has the positive
effect of promoting OL survival but the negative effect of preventing
their full differentiation. This finding clarifies many of the
paradoxical findings seen in the PLP mutants, the PLP overexpressers,
and the PLP
animals.
Key words:
oligodendrocytes;
myelin;
proteolipid protein;
antisense;
neuroglia;
survival