L Bugga | PubMed Health

PubMed1998

Analysis of neuronal and glial phenotypes in brains of mice deficient in leukemia inhibitory factor.

Leukemia inhibitory factor (LIF) can regulate the survival and differentiation of certain neurons and glial cells in culture. To determine the role of this cytokine in the central nervous system in vivo, we examined the brains of young and adult mice in which the LIF gene was disrupted. Immunohistochemical staining of neurons for choline acetyltransferase, tyrosine hydroxylase, serotonin, parvalbumin, calbindin, neuropeptide Y, vasoactive intestinal polypeptide, and calcitonin gene-related peptide revealed no significant differences between null mutant and wild-type (WT) brains. In contrast, analysis of glial phenotypes demonstrated striking deficits in the LIF-knockout brain. Staining with several anti-glial fibrillary acidic protein (GFAP) antibodies showed that the number of GFAP-positive cells in various regions of the hippocampus in the female mutant is much lower than in the WT. The null male hippocampus also displays a significant, though less marked deficit. The number of astrocytes in the mutant hippocampus, as determined by S-100 staining, is not, however, significantly different from WT. In addition, quantification of immunohistochemical staining of female, but not male, mutants reveals a significant deficit in myelin basic protein content in three brain regions, suggesting alterations in oligodendrocytes as well. Thus, while overall brain histology appears normal, the absence of LIF in vivo leads to specific, sexually dimorphic alterations in glial phenotype.

Animals↗

PubMed1992

Connexin expression and gap junction communication compartments in the developing mouse limb.

Fundamental to the understanding of mouse limb morphogenesis and pattern formation is the need to elucidate the spatial and temporal distribution of gap junction proteins (connexins, Cx) and cell-cell communication compartments. To this end, we used immunofluorescence and confocal microscopy together with 3-dimensional reconstruction software to map the distribution of Cx43 and Cx32 in 11-14.5 days postcoitum (dpc) mouse limbs. Cx43 was strictly localized to the apical ectodermal ridge (AER) and nonridge ectoderm throughout all stages of mouse limb development studied. Cx32, on the other hand, was abundant in the mesenchyme with only low levels of expression in the 11-13.5 dpc ectoderm. However, at 14-14.5 dpc there was a clear increase in Cx32 expression in the ectoderm. Double labeling for connexins and confocal microscopy revealed Cx43 and Cx32 in the same optical section of the basal cells of the ectoderm but in separate plaques. Lucifer yellow dye injections showed that the cells of the AER were in direct communication with the nonridge ectoderm but dye was never observed to spread to the mesenchyme. Cells of the mesenchyme were coupled to each other but to a much lesser extent than cells of the ectoderm. Finally, although there was an increase in Cx32 expression in the ectoderm at 14-14.5 dpc, this was not correlated with any detectable change in communication compartments. Thus, the lack of dye transfer between the ectoderm and underlying mesenchyme from the peak of AER height through its decline suggests that bulk transfer of morphogens between these two layers is not necessary for mouse limb development.

Animals↗