Developmental Expression of Wnt Signaling Factors in Mouse Brain

Abstract

The Wnt signaling pathway has been implicated in a variety of biological events inducing neurogenesis. In this study, we aim to investigate the expression pattern of various components of the Wnt pathway including β-catenin and its partners LEF-1/TCF-4, GSK-3β and their nuclear target genes such as c-myc and cyclin D1 during mouse brain development. We performed a series of Western blot and immunohistochemistry of brain cortex, brainstem, and cerebellum which revealed differential accumulation of these proteins in different types of brain cells including neurons, astrocytes, and oligodendrocytes at different developmental stages. Intense cytoplasmic immunolabeling of β-catenin in 5 day old neurons throughout the cortex and brainstem significantly decreased as the brain developed, whereas the level of GSK-3β, the protein that phosphorylates β-catenin and causes its destabilization, increased during brain maturation. On the other hand, high level accumulation of LEF-1 and TCF-4 in neurons and astrocytes at the early stage of brain development diminished at the later stages. Interestingly, while the majority of LEF-1 and TCF-4 immunoreactivity was detected in the cytoplasm of neurons, it was evident that both proteins accumulated in the nuclei of astrocytes. Examination of cyclin D1, a protein that controls the cell cycle and proliferation, exhibited an intense staining in the nuclei of astrocytes throughout brain parenchyma during development. Interestingly, cyclin D was found in the cytoplasm of neurons from cortex, brainstem, and cerebellum during brain development. These data provide compelling evidence for the differential expression of the Wnt signaling pathway during brain development, and suggest that these signaling pathways may function differently in various brain regions and cell types.

GSK3β negatively regulates oligodendrocyte differentiation and myelination in vivo

“…There is little b-catenin immunostaining in the control CC (Fig. 5B), consistent with a postnatal loss of Wnt-b-catenin signaling in developing white matter (Coyle-Rink et al, 2002;Takahashi et al, 1994). In contrast, cellular b-catenin is evident following ARA-014418 treatment, and confocal analysis in single z-sections shows that nuclear translocation of b-catenin is localized to Sox101 OL lineage cells (Fig.…”

“…Glycogen synthase kinase 3b (GSK3b) is a multifactorial negative regulator of cell fate that is a target of many receptor-mediated signaling pathways (Cohen and Goedert, 2004;Grimes and Jope 2001b). The functions of GSK3b signaling in OLs have not been previously determined, but GSK3b has high expression and activity in developing white matter (Coyle-Rink et al, 2002;Takahashi et al, 1994), and inhibition of GSK3b is a major effect of receptor kinase activation that mediates the prosurvival effects of insulin-like growth factor 1 (IGF-1) and fibroblast growth factor 2 (FGF-2) on OPs (Frederick et al, 2007;Ye et al, 2010). In addition, GSK3b is a key regulatory factor in the Wnt signaling pathway, which is a potent negative regulator of OL differentiation and myelination (Fancy et al, 2009;Feigenson et al, 2009) and is involved in the mitogenic actions of IGF-1 in OPs (Ye et al, 2010).…”

Trolox and 17β-Estradiol Protect against Amyloid β-Peptide Neurotoxicity by a Mechanism That Involves Modulation of the Wnt Signaling Pathway

“…Besides, vitamin C can increase the expression of developmental genes in neuronal cells and does not induce any changes in neuronal cell death protection genes (81). Additionally, Western blot and immunohistochemistry for ␤-catenin in brain cortex, brain stem, and cerebellum revealed differential accumulation of this protein in different types of brain cells including neurons, astrocytes, and oligodendrocytes at different developmental stages (82). E 2 has been reported as a neuroprotective agent against A␤ , A␤ , and A␤ [25][26][27][28][29][30][31][32][33][34][35] in assays at 4 -48 h on HT22 cells (11), hippocampal cells (14), and PC12 and Neuro-2a cells (15,83).…”

LEF1/β-Catenin Complex Regulates Transcription of the Cav3.1 Calcium Channel Gene (Cacna1g) in Thalamic Neurons of the Adult Brain

“…After birth, Lef1 mRNA levels dramatically decrease in the brain (Coyle-Rink et al, 2002) and can be detected only in the thalamus (Jones and Rubenstein, 2004;Shimogori et al, 2004). The role of LEF1 in the thalamus of the adult brain, however, is unknown.…”