Maintenance of the relative proportion of oligodendrocytes to axons even in the absence of BAX and BAK.
Highly purified oligodendroglial lineage cells from mice lacking functional bax and bak genes were resistant to apoptosis after in-vitro differentiation, indicating an essential role of the intrinsic apoptotic pathway in apoptosis of oligodendrocytes in the absence of neurons (axons) and other glial cells. These mice therefore provide a valuable tool with which to evaluate the significance of the intrinsic apoptotic pathway in regulating the population sizes of oligodendrocytes and oligodendroglial progenitor cells. Quantitative analysis of the optic nerves and the dorsal columns of the spinal cord revealed that the absolute numbers of mature oligodendrocytes immunolabeled for aspartoacylase and adult glial progenitor cells expressing NG2 chondroitin sulfate proteoglycan were increased in both white matter tracts of adult bax/bak-deficient mice and, to a lesser extent, bax-deficient mice, except that there was no increase in NG2-positive progenitor cells in the dorsal columns of these strains of mutant mice. These increases in mature oligodendrocytes and progenitor cells in bax/bak-deficient mice were unexpectedly proportional to increases in numbers of axons in these white matter tracts, thus retaining the oligodendroglial lineage to axon ratios of at most 1.3-fold of the physiological numbers. This is in contrast to the prominent expansion in numbers of neural precursor cells in the subventricular zones of these adult mutant mice. Our study indicates that homeostatic control of cell number is different for progenitors of the oligodendroglial and neuronal lineages. Furthermore, regulatory mechanism(s) operating in addition to apoptotic elimination through the intrinsic pathway, appear to prevent the overproduction of highly mitotic oligodendroglial progenitor cells.
Department of Neurology, University of California, School of Medicine, Sacramento, CA, USA.
Kumi
K
Kawai
Takayuki
T
Itoh
Aki
A
Itoh
Makoto
M
Horiuchi
Kouji
K
Wakayama
Peter
P
Bannerman
James Y
JY
Garbern
David
D
Pleasure
Tullia
T
Lindsten
D000818:Animals; D000831:Animals, Newborn; D000941:Antigens / Q000378:metabolism; D017209:Apoptosis / Q000235:genetics; D001369:Axons / Q000502:physiology*; D001921:Brain / Q000166:cytology; D016923:Cell Death / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D002478:Cells, Cultured; D005732:Gangliosides / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics; D020287:In Situ Nick-End Labeling / Q000379:methods; D051379:Mice; D018345:Mice, Knockout; D004676:Myelin Basic Protein / Q000378:metabolism; D009186:Myelin Sheath / Q000378:metabolism; D019081:O Antigens / Q000378:metabolism; D009836:Oligodendroglia / Q000502:physiology*; D009900:Optic Nerve / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D011509:Proteoglycans / Q000378:metabolism; D051560:Proto-Oncogene Proteins c-bcl-6 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013234:Stem Cells / Q000502:physiology; D013997:Time Factors; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000172:deficiency* / Q000235:genetics; D051028:bcl-2-Associated X Protein / Q000172:deficiency* / Q000235:genetics; D000099216:Chondroitin Sulfate Proteoglycan 4
D000941:Antigens; D005732:Gangliosides; D004676:Myelin Basic Protein; D019081:O Antigens; D011509:Proteoglycans; D051560:Proto-Oncogene Proteins c-bcl-6; D012333:RNA, Messenger; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D000099216:Chondroitin Sulfate Proteoglycan 4; C494773:Bak1 protein, mouse; C494827:Bax protein, mouse; C062875:ganglioside A2B5