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Updated: Aug 10, 2026
Live-imaging of the Drosophila Pupal Eye
Published on: January 12, 2015
smoothened and thickveins regulate Moleskin/Importin 7-mediated MAP kinase signaling in the developing Drosophila eye
Alysia D Vrailas1, Daniel R Marenda, Summer E Cook
1Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA.
Abstract:
The Drosophila Mitogen Activated Protein Kinase (MAPK) Rolled is a key regulator of developmental signaling, relaying information from the cytoplasm into the nucleus. Cytoplasmic MEK phosphorylates MAPK (pMAPK), which then dimerizes and translocates to the nucleus where it regulates transcription factors. In cell culture, MAPK nuclear translocation directly follows phosphorylation, but in developing tissues pMAPK can be held in the cytoplasm for extended periods (hours). Here, we show that Moleskin antigen (Drosophila Importin 7/Msk), a MAPK transport factor, is sequestered apically at a time when lateral inhibition is required for patterning in the developing eye. We suggest that this apical restriction of Msk limits MAPK nuclear translocation and blocks Ras pathway nuclear signaling. Ectopic expression of Msk overcomes this block and disrupts patterning. Additionally, the MAPK cytoplasmic hold is genetically dependent on the presence of Decapentaplegic (Dpp) and Hedgehog receptors.
Insights
Drosophila Importin 7 (Msk) restricts Mitogen Activated Protein Kinase (MAPK) nuclear entry during eye development. This apical Msk sequestration blocks Ras pathway signaling, impacting tissue patterning.
Area of Science:
- Developmental Biology
- Cell Signaling
- Molecular Biology
Background:
- Mitogen Activated Protein Kinase (MAPK) signaling regulates gene transcription by translocating from the cytoplasm to the nucleus.
- In Drosophila, MAPK nuclear translocation is rapid in cell culture but delayed in developing tissues.
- The mechanisms controlling cytoplasmic sequestration of phosphorylated MAPK (pMAPK) in vivo are not fully understood.
Purpose of the Study:
- To investigate the role of Moleskin (Msk), a Drosophila Importin 7 homolog, in regulating MAPK nuclear translocation during eye development.
- To determine how Msk localization affects Ras pathway signaling and tissue patterning.
- To identify genetic factors involved in the cytoplasmic retention of pMAPK.
Main Methods:
- Immunohistochemistry to visualize Msk localization in developing Drosophila eyes.
- Genetic manipulation (ectopic expression) of Msk to assess its effects on MAPK localization and eye patterning.
- Genetic analysis of interactions between Msk, Decapentaplegic (Dpp), and Hedgehog (Hh) signaling pathways.
Main Results:
- Moleskin (Msk) is apically sequestered in the developing eye during critical patterning stages.
- Apical Msk restriction limits MAPK nuclear translocation and inhibits Ras pathway signaling.
- Ectopic Msk expression disrupts eye patterning by overcoming the MAPK cytoplasmic hold.
- The cytoplasmic retention of MAPK is genetically dependent on Decapentaplegic (Dpp) and Hedgehog (Hh) receptors.
Conclusions:
- Moleskin (Msk) acts as a critical regulator of MAPK nuclear import by controlling its subcellular localization.
- Apical Msk sequestration provides a mechanism for spatially and temporally restricting Ras pathway signaling during Drosophila eye development.
- The interplay between Msk, Dpp, and Hh signaling pathways is essential for proper tissue patterning.
