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Distribution of microtubules containing post-translationally modified alpha-tubulin during Drosophila embryogenesis
R M Warn1, A Harrison, V Planques
1School of Biological Sciences, University of East Anglia, Norwich, England.
Abstract:
The distribution of microtubules (MTs) enriched in detyrosinated alpha-tubulin (Glu-tubulin) was studied in Drosophila embryos by immunofluorescence microscopy by using a monoclonal antibody (ID5) which was raised against a 14-residue synthetic peptide spanning the carboxyterminal sequence of Glu-tubulin (Wehland and Weber: J. Cell Sci. 88:185-203, 1987). While all MT arrays contained tyrosinated alpha-tubulin (Tyr-tubulin), MTs rich in Glu-tubulin were not found during early stages of development even by using an image intensification camera. Elevated levels of microtubular Glu-tubulin were first detected after CNS condensation in neurone processes. In addition, sperm tails, which remained remarkably stable inside the embryo until late stages of development, were decorated by ID5. This was in marked contrast to the distribution of microtubule arrays containing acetylated alpha-tubulin, which could already be detected during the cellular blastoderm stage. Additional experiments with taxol suggested that the absence of MTs rich in Glu-tubulin during early stages of development was not due to the rapid turnover rate of MTs, which would be too fast for alpha-tubulin to be detyrosinated. The possible significance of the differential detyrosination and acetylation of microtubules during development is discussed.
Insights
Microtubules rich in detyrosinated alpha-tubulin (Glu-tubulin) are absent in early Drosophila development, appearing later in neuronal processes. This contrasts with acetylated alpha-tubulin, present from the blastoderm stage.
Area of Science:
- Cell Biology
- Developmental Biology
- Molecular Biology
Background:
- Microtubules (MTs) are dynamic cytoskeletal polymers crucial for cellular processes.
- Alpha-tubulin undergoes post-translational modifications, including tyrosination and detyrosination, affecting MT stability and function.
- Detyrosinated alpha-tubulin (Glu-tubulin) is a marker for stable microtubules, but its developmental distribution is not fully understood.
Purpose of the Study:
- To investigate the spatial and temporal distribution of detyrosinated alpha-tubulin (Glu-tubulin) in Drosophila embryos during development.
- To compare the distribution of Glu-tubulin with tyrosinated alpha-tubulin (Tyr-tubulin) and acetylated alpha-tubulin.
- To explore the factors influencing the presence of Glu-tubulin during early embryonic development.
Main Methods:
- Immunofluorescence microscopy using a specific monoclonal antibody (ID5) against Glu-tubulin.
- Analysis of microtubule distribution in Drosophila embryos at various developmental stages.
- Experimental manipulation with taxol to assess the role of MT turnover rate.
Main Results:
- Tyrosinated alpha-tubulin (Tyr-tubulin) was detected in all MT arrays throughout development.
- Microtubules enriched in Glu-tubulin were not observed in early developmental stages, even with enhanced imaging.
- Elevated Glu-tubulin levels were first detected in neuronal processes after central nervous system condensation.
- Stable sperm tails within the embryo were also decorated by the anti-Glu-tubulin antibody.
- In contrast, acetylated alpha-tubulin was detectable as early as the cellular blastoderm stage.
- Taxol experiments suggested that rapid MT turnover was not the reason for the absence of Glu-tubulin in early stages.
Conclusions:
- Detyrosination of alpha-tubulin is a late event in Drosophila embryonic development, specifically associated with neuronal differentiation and stable structures like sperm tails.
- The differential timing of Glu-tubulin and acetylated alpha-tubulin accumulation suggests distinct roles and regulatory mechanisms for these modifications during development.
- The absence of Glu-tubulin in early development is unlikely due to rapid microtubule turnover.