The Journal of Neuroscience, February 1, 2006, 26(5):1439-1447; doi:10.1523/JNEUROSCI.2219-05.2006
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Development/Plasticity/Repair
Proliferation and Death of Oligodendrocytes and Myelin Proteins Are Differentially Regulated in Male and Female Rodents
Mirela Cerghet,1,2
Robert P. Skoff,2
Denise Bessert,2
Zhan Zhang,2
Chadwick Mullins,2 and
M. Said Ghandour3
1Department of Neurology, Henry Ford Hospital, Detroit, Michigan 48202, 2Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, and 3Institut de Physique Biologique, Unité Mixte de Recherche 7004, Strasbourg 67085, France
Correspondence should be addressed to Robert P. Skoff, Department of Anatomy and Cell Biology, Wayne State University School of Medicine, 540 East Canfield, Detroit, MI 48201. Email: rskoff{at}med.wayne.edu
Sexual dimorphism of neurons and astrocytes has been demonstrated in different centers of the brain, but sexual dimorphism of oligodendrocytes and myelin has not been examined. We show, using immunocytochemistry and in situ hybridization, that the density of oligodendrocytes in corpus callosum, fornix, and spinal cord is 2040% greater in males compared with females. These differences are present in young and aged rodents and are independent of strain and species. Proteolipid protein and carbonic anhydrase-II transcripts, measured by real-time PCR, are approximately two to three times greater in males. Myelin basic protein and 2', 3'-cyclic nucleotide 3'-phosphodiesterase, measured by Western blots, are 20160% greater in males compared with females. Surprisingly, both generation of new glia and apoptosis of glia, including oligodendrocytes, are approximately two times greater in female corpus callosum. These results indicate that the lifespan of oligodendrocytes is shorter in females than in males. Castration of males produces a female phenotype characterized by fewer oligodendrocytes and increased generation of new glia. These findings indicate that exogenous androgens differentially affect the lifespan of male and female oligodendrocytes, and they can override the endogenous production of neurosteroids. The data imply that turnover of myelin is greater in females than in males. µ-Calpain, a protease upregulated in degeneration of myelin, is dramatically increased at both transcriptional and translational levels in females compared with males. These morphological, molecular, and biochemical data show surprisingly large differences in turnover of oligodendrocytes and myelin between sexes. We discuss the potential significance of these differences to multiple sclerosis, a sexually dimorphic disease, whose progression is altered by exogenous hormones.
Key words: oligodendrocyte; myelin; sexual dimorphism; proliferation; apoptosis; estrogen; estradiol
Received June 1, 2005;
revised Dec. 19, 2005;
accepted Dec. 20, 2005.
Correspondence should be addressed to Robert P. Skoff, Department of Anatomy and Cell Biology, Wayne State University School of Medicine, 540 East Canfield, Detroit, MI 48201. Email: rskoff{at}med.wayne.edu
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