Related Experiment Video
Updated: May 31, 2026
Examination of Drosophila Larval Tracheal Terminal Cells by Light Microscopy
Published on: July 9, 2013
A systematic screen for tube morphogenesis and branching genes in the Drosophila tracheal system
Amin S Ghabrial1, Boaz P Levi, Mark A Krasnow
1Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, USA. ghabrial@mail.med.upenn.edu
Abstract:
Many signaling proteins and transcription factors that induce and pattern organs have been identified, but relatively few of the downstream effectors that execute morphogenesis programs. Because such morphogenesis genes may function in many organs and developmental processes, mutations in them are expected to be pleiotropic and hence ignored or discarded in most standard genetic screens. Here we describe a systematic screen designed to identify all Drosophila third chromosome genes (∼40% of the genome) that function in development of the tracheal system, a tubular respiratory organ that provides a paradigm for branching morphogenesis. To identify potentially pleiotropic morphogenesis genes, the screen included analysis of marked clones of homozygous mutant tracheal cells in heterozygous animals, plus a secondary screen to exclude mutations in general "house-keeping" genes. From a collection including more than 5,000 lethal mutations, we identified 133 mutations representing ∼70 or more genes that subdivide the tracheal terminal branching program into six genetically separable steps, a previously established cell specification step plus five major morphogenesis and maturation steps: branching, growth, tubulogenesis, gas-filling, and maintenance. Molecular identification of 14 of the 70 genes demonstrates that they include six previously known tracheal genes, each with a novel function revealed by clonal analysis, and two well-known growth suppressors that establish an integral role for cell growth control in branching morphogenesis. The rest are new tracheal genes that function in morphogenesis and maturation, many through cytoskeletal and secretory pathways. The results suggest systematic genetic screens that include clonal analysis can elucidate the full organogenesis program and that over 200 patterning and morphogenesis genes are required to build even a relatively simple organ such as the Drosophila tracheal system.
Insights
This study identified over 70 genes controlling Drosophila tracheal system development, revealing six key steps in branching morphogenesis. Clonal analysis helped uncover pleiotropic genes essential for organogenesis.
Area of Science:
- Developmental Biology
- Genetics
- Molecular Biology
Background:
- Organogenesis relies on signaling proteins and transcription factors, but downstream effectors executing morphogenesis are less understood.
- Pleiotropic genes, affecting multiple processes, are often missed in standard genetic screens.
Purpose of the Study:
- To systematically identify genes involved in Drosophila tracheal system development, particularly those with pleiotropic functions.
- To dissect the genetic control of branching morphogenesis in the tracheal system.
Main Methods:
- Conducted a systematic genetic screen of Drosophila third chromosome lethal mutations.
- Utilized marked clones of homozygous mutant tracheal cells in heterozygous animals to identify pleiotropic genes.
- Performed secondary screening to exclude general house-keeping genes.
Main Results:
- Identified 133 mutations representing over 70 genes essential for tracheal terminal branching.
- Discovered six genetically separable steps in tracheal morphogenesis: branching, growth, tubulogenesis, gas-filling, and maintenance.
- Molecular identification revealed known and novel tracheal genes, including growth suppressors, highlighting the role of cell growth control.
Conclusions:
- Systematic genetic screens with clonal analysis are effective for identifying comprehensive sets of organogenesis genes.
- Over 200 patterning and morphogenesis genes are required for constructing even simple organs like the Drosophila tracheal system.
- Cytoskeletal and secretory pathways are crucial for tracheal morphogenesis and maturation.
