Buffered EGFR signaling regulated by spitz-to-argos expression ratio is a critical factor for patterning the Drosophila eye

PLoS Genet. 2023 Feb 2;19(2):e1010622. doi: 10.1371/journal.pgen.1010622. eCollection 2023 Feb.


The Epidermal Growth Factor Receptor (EGFR) signaling pathway plays a critical role in regulating tissue patterning. Drosophila EGFR signaling achieves specificity through multiple ligands and feedback loops to finetune signaling outcomes spatiotemporally. The principal Drosophila EGF ligand, cleaved Spitz, and the negative feedback regulator, Argos are diffusible and can act both in a cell autonomous and non-autonomous manner. The expression dose of Spitz and Argos early in photoreceptor cell fate determination has been shown to be critical in patterning the Drosophila eye, but the exact identity of the cells expressing these genes in the larval eye disc has been elusive. Using single molecule RNA Fluorescence in situ Hybridization (smFISH), we reveal an intriguing differential expression of spitz and argos mRNA in the Drosophila third instar eye imaginal disc indicative of directional non-autonomous EGFR signaling. By genetically tuning EGFR signaling, we show that rather than absolute levels of expression, the ratio of expression of spitz-to-argos to be a critical determinant of the final adult eye phenotype. Proximate effects on EGFR signaling in terms of cell cycle and differentiation markers are affected differently in the different perturbations. Proper ommatidial patterning is robust to thresholds around a tightly maintained wildtype spitz-to-argos ratio, and breaks down beyond. This provides a powerful instance of developmental buffering against gene expression fluctuations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Drosophila Proteins* / genetics
  • Drosophila Proteins* / metabolism
  • Drosophila* / genetics
  • Epidermal Growth Factor / genetics
  • ErbB Receptors / genetics
  • ErbB Receptors / metabolism
  • Eye / metabolism
  • In Situ Hybridization, Fluorescence
  • Receptors, Invertebrate Peptide / genetics
  • Receptors, Invertebrate Peptide / metabolism
  • Signal Transduction / genetics


  • ErbB Receptors
  • Drosophila Proteins
  • Epidermal Growth Factor
  • Egfr protein, Drosophila
  • Receptors, Invertebrate Peptide

Grants and funding

This project was supported by intramural funds at TIFR Hyderabad from the Department of Atomic Energy, Government of India (Project Identification No. RTI 4007 to AM). MJ is a Ramalingaswami fellow, Department of Biotechnology, Government of India, under project number BT/RLF/Re-entry/06/2016. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.