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Conditional gene ablation of Stat3 reveals differential signaling requirements for survival of motoneurons during development and after nerve injury in the adult.

Schweizer U, Gunnersen J, Karch C, Wiese S, Holtmann B, Takeda K, Akira S, Sendtner M - J. Cell Biol. (2002)

Bottom Line: In contrast, motoneuron survival is significantly reduced after facial nerve lesion in the adult.Stat3 is essential for upregulation of Reg-2 and Bcl-xl expression in lesioned motoneurons.Our data show that Stat3 activation plays an essential role for motoneuron survival after nerve lesion in postnatal life but not during embryonic development, indicating that signaling requirements for motoneuron survival change during maturation.

View Article: PubMed Central - PubMed

Affiliation: Institute for Clinical Neurobiology, University of Würzburg, 97080 Würzburg, Germany.

ABSTRACT
Members of the ciliary neurotrophic factor (CNTF)/leukemia inhibitory factor (LIF)/cardiotrophin gene family are potent survival factors for embryonic and lesioned motoneurons. These factors act via receptor complexes involving gp130 and LIFR-beta and ligand binding leads to activation of various signaling pathways, including phosphorylation of Stat3. The role of Stat3 in neuronal survival was investigated in mice by Cre-mediated gene ablation in motoneurons. Cre is expressed under the neurofilament light chain (NF-L) promoter, starting around E12 when these neurons become dependent on neurotrophic support. Loss of motoneurons during the embryonic period of naturally occurring cell death is not enhanced in NF-L-Cre; Stat3(flox/KO) mice although motoneurons isolated from these mice need higher concentrations of CNTF for maximal survival in culture. In contrast, motoneuron survival is significantly reduced after facial nerve lesion in the adult. These neurons, however, can be rescued by the addition of neurotrophic factors, including CNTF. Stat3 is essential for upregulation of Reg-2 and Bcl-xl expression in lesioned motoneurons. Our data show that Stat3 activation plays an essential role for motoneuron survival after nerve lesion in postnatal life but not during embryonic development, indicating that signaling requirements for motoneuron survival change during maturation.

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Bcl-xl expression in axotomized facial motoneurons depends on Stat3. (A) RT-PCR analysis using total RNA derived from acutely isolated facial nuclei revealed an increase of Bcl-xl mRNA 2 d after facial nerve transection. In NF-L–Cre; Stat3flox/KO mice, Bcl-xl mRNA levels are only 65% of the amount in the NF-L–Cre; Stat3flox/wt littermates. This indicates that Stat3 is involved in the upregulation of Bcl-xl in motoneurons after axotomy (n = 5, P < 0.05, ANOVA with Bonferroni's post hoc comparison). Results shown are from one representative experiment of three experiments with similar results. (B) In situ hybridization reveals that Bcl-xl is specifically expressed in murine facial motoneurons, but not in surrounding glial cells. The bottom panel shows an adjacent section hybridized with the sense probe. Bar, 100 μm.
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fig6: Bcl-xl expression in axotomized facial motoneurons depends on Stat3. (A) RT-PCR analysis using total RNA derived from acutely isolated facial nuclei revealed an increase of Bcl-xl mRNA 2 d after facial nerve transection. In NF-L–Cre; Stat3flox/KO mice, Bcl-xl mRNA levels are only 65% of the amount in the NF-L–Cre; Stat3flox/wt littermates. This indicates that Stat3 is involved in the upregulation of Bcl-xl in motoneurons after axotomy (n = 5, P < 0.05, ANOVA with Bonferroni's post hoc comparison). Results shown are from one representative experiment of three experiments with similar results. (B) In situ hybridization reveals that Bcl-xl is specifically expressed in murine facial motoneurons, but not in surrounding glial cells. The bottom panel shows an adjacent section hybridized with the sense probe. Bar, 100 μm.

Mentions: We have also investigated other Stat3-regulated genes which modulate neuronal survival. Bcl-xl is highly expressed in various regions of the nervous system (Motoyama et al., 1995), including the facial nucleus (Hamner et al., 1999; Fig. 6 B). Using semiquantitative RT-PCR we found that Bcl-xl expression is induced 8.13 ± 2.02-fold at 48 h after axotomy in the facial nucleus of control NF-L–Cre; Stat3flox/wt mice. In the facial nucleus of NF-L–Cre; Stat3flox/KO littermates, Bcl-xl expression is induced 5.3 ± 0.46-fold (means calculated from three experiments). Thus, in NF-L–Cre; Stat3flox/KO mice Bcl-xl expression in the facial nucleus is only 65% of that observed in NF-L–Cre; Stat3flox/wt (n = 3–5; P < 0.05), indicating that Stat3 significantly contributes to the upregulation of Bcl-xl in lesioned motoneurons (Fig. 6 A). In addition, we tested the expression of Bcl-2 and Bcl-w in the facial nucleus on the lesioned and the control side of NF-L–Cre; Stat3flox/KO and NF-L–Cre; Stat3flox/wt mice. None of these two genes was significantly induced after axotomy, independent of the presence or absence of Stat3 (Table III). Similarly, expression of Bax, a proapoptotic member of this family was similar in NF-L–Cre; Stat3flox/wt and NF-L–Cre; Stat3flox/KO mice, and no up-regulation was observed on the lesioned side on the mRNA level.


Conditional gene ablation of Stat3 reveals differential signaling requirements for survival of motoneurons during development and after nerve injury in the adult.

Schweizer U, Gunnersen J, Karch C, Wiese S, Holtmann B, Takeda K, Akira S, Sendtner M - J. Cell Biol. (2002)

Bcl-xl expression in axotomized facial motoneurons depends on Stat3. (A) RT-PCR analysis using total RNA derived from acutely isolated facial nuclei revealed an increase of Bcl-xl mRNA 2 d after facial nerve transection. In NF-L–Cre; Stat3flox/KO mice, Bcl-xl mRNA levels are only 65% of the amount in the NF-L–Cre; Stat3flox/wt littermates. This indicates that Stat3 is involved in the upregulation of Bcl-xl in motoneurons after axotomy (n = 5, P < 0.05, ANOVA with Bonferroni's post hoc comparison). Results shown are from one representative experiment of three experiments with similar results. (B) In situ hybridization reveals that Bcl-xl is specifically expressed in murine facial motoneurons, but not in surrounding glial cells. The bottom panel shows an adjacent section hybridized with the sense probe. Bar, 100 μm.
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Related In: Results  -  Collection

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fig6: Bcl-xl expression in axotomized facial motoneurons depends on Stat3. (A) RT-PCR analysis using total RNA derived from acutely isolated facial nuclei revealed an increase of Bcl-xl mRNA 2 d after facial nerve transection. In NF-L–Cre; Stat3flox/KO mice, Bcl-xl mRNA levels are only 65% of the amount in the NF-L–Cre; Stat3flox/wt littermates. This indicates that Stat3 is involved in the upregulation of Bcl-xl in motoneurons after axotomy (n = 5, P < 0.05, ANOVA with Bonferroni's post hoc comparison). Results shown are from one representative experiment of three experiments with similar results. (B) In situ hybridization reveals that Bcl-xl is specifically expressed in murine facial motoneurons, but not in surrounding glial cells. The bottom panel shows an adjacent section hybridized with the sense probe. Bar, 100 μm.
Mentions: We have also investigated other Stat3-regulated genes which modulate neuronal survival. Bcl-xl is highly expressed in various regions of the nervous system (Motoyama et al., 1995), including the facial nucleus (Hamner et al., 1999; Fig. 6 B). Using semiquantitative RT-PCR we found that Bcl-xl expression is induced 8.13 ± 2.02-fold at 48 h after axotomy in the facial nucleus of control NF-L–Cre; Stat3flox/wt mice. In the facial nucleus of NF-L–Cre; Stat3flox/KO littermates, Bcl-xl expression is induced 5.3 ± 0.46-fold (means calculated from three experiments). Thus, in NF-L–Cre; Stat3flox/KO mice Bcl-xl expression in the facial nucleus is only 65% of that observed in NF-L–Cre; Stat3flox/wt (n = 3–5; P < 0.05), indicating that Stat3 significantly contributes to the upregulation of Bcl-xl in lesioned motoneurons (Fig. 6 A). In addition, we tested the expression of Bcl-2 and Bcl-w in the facial nucleus on the lesioned and the control side of NF-L–Cre; Stat3flox/KO and NF-L–Cre; Stat3flox/wt mice. None of these two genes was significantly induced after axotomy, independent of the presence or absence of Stat3 (Table III). Similarly, expression of Bax, a proapoptotic member of this family was similar in NF-L–Cre; Stat3flox/wt and NF-L–Cre; Stat3flox/KO mice, and no up-regulation was observed on the lesioned side on the mRNA level.

Bottom Line: In contrast, motoneuron survival is significantly reduced after facial nerve lesion in the adult.Stat3 is essential for upregulation of Reg-2 and Bcl-xl expression in lesioned motoneurons.Our data show that Stat3 activation plays an essential role for motoneuron survival after nerve lesion in postnatal life but not during embryonic development, indicating that signaling requirements for motoneuron survival change during maturation.

View Article: PubMed Central - PubMed

Affiliation: Institute for Clinical Neurobiology, University of Würzburg, 97080 Würzburg, Germany.

ABSTRACT
Members of the ciliary neurotrophic factor (CNTF)/leukemia inhibitory factor (LIF)/cardiotrophin gene family are potent survival factors for embryonic and lesioned motoneurons. These factors act via receptor complexes involving gp130 and LIFR-beta and ligand binding leads to activation of various signaling pathways, including phosphorylation of Stat3. The role of Stat3 in neuronal survival was investigated in mice by Cre-mediated gene ablation in motoneurons. Cre is expressed under the neurofilament light chain (NF-L) promoter, starting around E12 when these neurons become dependent on neurotrophic support. Loss of motoneurons during the embryonic period of naturally occurring cell death is not enhanced in NF-L-Cre; Stat3(flox/KO) mice although motoneurons isolated from these mice need higher concentrations of CNTF for maximal survival in culture. In contrast, motoneuron survival is significantly reduced after facial nerve lesion in the adult. These neurons, however, can be rescued by the addition of neurotrophic factors, including CNTF. Stat3 is essential for upregulation of Reg-2 and Bcl-xl expression in lesioned motoneurons. Our data show that Stat3 activation plays an essential role for motoneuron survival after nerve lesion in postnatal life but not during embryonic development, indicating that signaling requirements for motoneuron survival change during maturation.

Show MeSH
Related in: MedlinePlus