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Updated: Jul 25, 2026

Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development
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Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development

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Signalling by the sevenless protein tyrosine kinase is mimicked by Ras1 activation

M E Fortini1, M A Simon, G M Rubin

  • 1Howard Hughes Medical Institute, University of California, Berkeley 94720.

Nature
|February 6, 1992
PubMed

Insights

Ras1 activation is crucial for Drosophila R7 photoreceptor development, mediating signals from the sevenless receptor. Activating Ras1 rescues R7 cell fate and can induce extra R7 cells, showing Ras protein specificity.

Area of Science:

  • Developmental biology
  • Cell signaling
  • Genetics

Background:

  • R7 photoreceptor cell-fate specification in Drosophila is a model for understanding receptor tyrosine kinase signaling.
  • The sevenless (sev) receptor, activated by the bride-of-sevenless (boss) ligand, is essential for R7 development.
  • Ras1 signaling is implicated in sev-mediated cell fate determination.

Purpose of the Study:

  • To investigate the role of Ras1 activation in sevenless (Sev) signaling during Drosophila R7 photoreceptor development.
  • To determine if Ras1 activation is sufficient to mediate all signaling functions of Sev.
  • To assess the specificity of Ras protein involvement in this pathway.

Main Methods:

  • Utilized Drosophila genetic mutants (sev, boss null mutants).
  • Introduced activated Ras1Va112 protein into R7 precursors.
  • Observed the effects of Ras1 activation on R7 cell fate and supernumerary R7 cell formation.
  • Compared the effects of Ras1 activation with Ras2 activation.

Main Results:

  • Activated Ras1Va112 rescued R7 precursors in sev and boss null mutants, preventing their transformation into cone cells.
  • Activated Ras1Va112 induced the formation of supernumerary R7 cells.
  • Activation of Drosophila Ras2 protein did not yield similar results, indicating specificity.

Conclusions:

  • Ras1 activation is sufficient to account for the signaling activity of the sevenless receptor.
  • Ras1 acts downstream of Sev and Boss in the R7 cell-fate specification pathway.
  • The study highlights the specific role of Ras1 in mediating inductive signaling for photoreceptor development.

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