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Disruption of microtubule integrity initiates mitosis during CNS repair.

Bossing T, Barros CS, Fischer B, Russell S, Shepherd D - Dev. Cell (2012)

Bottom Line: A pilot screen analyzing transcriptomes of single cells during repair pointed to downregulation of the microtubule-stabilizing GTPase mitochondrial Rho (Miro) and upregulation of the Jun transcription factor Jun-related antigen (Jra).Conversely, loss of Jra renders midline cells unable to replace damaged siblings.The conservation of the identified molecules suggests that similar mechanisms may operate in vertebrates.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Bangor University, Deiniol Road, Bangor LL57 2UW, UK. t.bossing@bangor.ac.uk

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Jra, the Drosophila Jun Ortholog, Is Essential for Midline RepairGenotypes are listed on top of panels. Ventral views, anterior up. Bar 5 μm.(A and B) In heterozygous embryos (A), but not in Jra mutant embryos (B), removal of midline cells (green, arrowhead marks gap) triggers mitosis (arrows; pH3, red).(C) In heterozygous embryos, ablation of midline siblings leads to replacement of the ablated cell.(D) After ablation of one sibling in Jra mutants, the surviving sibling does not divide or differentiate.(E) Replacement of ablated sibling cells in heterozygous (JraIA109/Cyo, n = 21) and mutant (JraIA109/ JraIA109, n = 14) embryos. No repair, undamaged sibling does not divide; repair, undamaged sibling divides; dead, undamaged sibling dies.(F and G) At stage 13, in wild-type, jra mRNA (red) is not detectable in midline cells (green, F) but midline expression of α-tubulin activates jra transcription (red, G). Insets only show the red channel at the midline.See also Figure S4.
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fig4: Jra, the Drosophila Jun Ortholog, Is Essential for Midline RepairGenotypes are listed on top of panels. Ventral views, anterior up. Bar 5 μm.(A and B) In heterozygous embryos (A), but not in Jra mutant embryos (B), removal of midline cells (green, arrowhead marks gap) triggers mitosis (arrows; pH3, red).(C) In heterozygous embryos, ablation of midline siblings leads to replacement of the ablated cell.(D) After ablation of one sibling in Jra mutants, the surviving sibling does not divide or differentiate.(E) Replacement of ablated sibling cells in heterozygous (JraIA109/Cyo, n = 21) and mutant (JraIA109/ JraIA109, n = 14) embryos. No repair, undamaged sibling does not divide; repair, undamaged sibling divides; dead, undamaged sibling dies.(F and G) At stage 13, in wild-type, jra mRNA (red) is not detectable in midline cells (green, F) but midline expression of α-tubulin activates jra transcription (red, G). Insets only show the red channel at the midline.See also Figure S4.

Mentions: Jun is a transcription factor found to be upregulated in vertebrate brain injury (Raivich and Behrens, 2006). Interestingly we observed upregulation of the Drosophila Jun ortholog, Jra, in our exploratory microarray analysis (T.B. et al., unpublished data). To test if Jra is necessary for damage-induced division, we first performed mass ablation of midline cells in JraIA109 mutants. In heterozygous embryos, tissue repair is still observed (4/9; Figure 4A) but in Jra homozygous mutants injury no longer activates midline cell division (0/5; Figure 4B). Without damage, we detect no significant changes in midline cell divisions between heterozygous and homozygous Jra mutant embryos (Figures S4D–S4F). We next ablated single cells in heterozygous and homozygous Jra mutant embryos. In heterozygous embryos, single ablated sibling cells were mostly replaced (62%, n = 21; Figures 4C and 4E); however, in Jra homozygotes the replacement of ablated single cells is the exception (14%). The majority of surviving siblings do not divide or differentiate (57%, n = 14; Figures 4D and 4E). Since midline expression of α-tubulin drives midline cells into division, we tested if α-tubulin expression is sufficient to switch on Jra transcription. Indeed, midline targeted α-tubulin induces ectopic Jra expression (Figures 4F and 4G).


Disruption of microtubule integrity initiates mitosis during CNS repair.

Bossing T, Barros CS, Fischer B, Russell S, Shepherd D - Dev. Cell (2012)

Jra, the Drosophila Jun Ortholog, Is Essential for Midline RepairGenotypes are listed on top of panels. Ventral views, anterior up. Bar 5 μm.(A and B) In heterozygous embryos (A), but not in Jra mutant embryos (B), removal of midline cells (green, arrowhead marks gap) triggers mitosis (arrows; pH3, red).(C) In heterozygous embryos, ablation of midline siblings leads to replacement of the ablated cell.(D) After ablation of one sibling in Jra mutants, the surviving sibling does not divide or differentiate.(E) Replacement of ablated sibling cells in heterozygous (JraIA109/Cyo, n = 21) and mutant (JraIA109/ JraIA109, n = 14) embryos. No repair, undamaged sibling does not divide; repair, undamaged sibling divides; dead, undamaged sibling dies.(F and G) At stage 13, in wild-type, jra mRNA (red) is not detectable in midline cells (green, F) but midline expression of α-tubulin activates jra transcription (red, G). Insets only show the red channel at the midline.See also Figure S4.
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Related In: Results  -  Collection

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fig4: Jra, the Drosophila Jun Ortholog, Is Essential for Midline RepairGenotypes are listed on top of panels. Ventral views, anterior up. Bar 5 μm.(A and B) In heterozygous embryos (A), but not in Jra mutant embryos (B), removal of midline cells (green, arrowhead marks gap) triggers mitosis (arrows; pH3, red).(C) In heterozygous embryos, ablation of midline siblings leads to replacement of the ablated cell.(D) After ablation of one sibling in Jra mutants, the surviving sibling does not divide or differentiate.(E) Replacement of ablated sibling cells in heterozygous (JraIA109/Cyo, n = 21) and mutant (JraIA109/ JraIA109, n = 14) embryos. No repair, undamaged sibling does not divide; repair, undamaged sibling divides; dead, undamaged sibling dies.(F and G) At stage 13, in wild-type, jra mRNA (red) is not detectable in midline cells (green, F) but midline expression of α-tubulin activates jra transcription (red, G). Insets only show the red channel at the midline.See also Figure S4.
Mentions: Jun is a transcription factor found to be upregulated in vertebrate brain injury (Raivich and Behrens, 2006). Interestingly we observed upregulation of the Drosophila Jun ortholog, Jra, in our exploratory microarray analysis (T.B. et al., unpublished data). To test if Jra is necessary for damage-induced division, we first performed mass ablation of midline cells in JraIA109 mutants. In heterozygous embryos, tissue repair is still observed (4/9; Figure 4A) but in Jra homozygous mutants injury no longer activates midline cell division (0/5; Figure 4B). Without damage, we detect no significant changes in midline cell divisions between heterozygous and homozygous Jra mutant embryos (Figures S4D–S4F). We next ablated single cells in heterozygous and homozygous Jra mutant embryos. In heterozygous embryos, single ablated sibling cells were mostly replaced (62%, n = 21; Figures 4C and 4E); however, in Jra homozygotes the replacement of ablated single cells is the exception (14%). The majority of surviving siblings do not divide or differentiate (57%, n = 14; Figures 4D and 4E). Since midline expression of α-tubulin drives midline cells into division, we tested if α-tubulin expression is sufficient to switch on Jra transcription. Indeed, midline targeted α-tubulin induces ectopic Jra expression (Figures 4F and 4G).

Bottom Line: A pilot screen analyzing transcriptomes of single cells during repair pointed to downregulation of the microtubule-stabilizing GTPase mitochondrial Rho (Miro) and upregulation of the Jun transcription factor Jun-related antigen (Jra).Conversely, loss of Jra renders midline cells unable to replace damaged siblings.The conservation of the identified molecules suggests that similar mechanisms may operate in vertebrates.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Bangor University, Deiniol Road, Bangor LL57 2UW, UK. t.bossing@bangor.ac.uk

Show MeSH
Related in: MedlinePlus