Correct regionalization of a tissue primordium is essential for coordinated morphogenesis

Area of Science:

• Developmental Biology
• Cell Biology
• Genetics

Background:

• Tubular organs form from flat epithelial sheets during development.
• Previous work identified cell wedging, tilting, and intercalation in Drosophila salivary gland placodes for tube initiation.

Purpose of the Study:

• Investigate requirements for continuous, narrow, symmetrical tube formation from asymmetrical primordia.
• Understand how changing tissue geometry affects organ development.

Main Methods:

• Live imaging and quantitative analysis.
• Comparison of wild-type and mutant Drosophila embryos with disrupted cell behaviors or initial symmetry.
• Analysis of transcriptional patterning and downstream morphogenetic modules.

Main Results:

• Early transcriptional patterning of morphogenetic factors drives selective activation of downstream modules like GPCR signaling.
• Apical-medial actomyosin activity induces cell wedging at the invagination point.
• Transcription expands, and cell behaviors shift from intercalation to apical constriction as cells approach the invagination pit.
• Misplacement or enlargement of the invagination pit impairs cell behaviors and organ shape.

Conclusions:

• Dynamic transcription factor patterning ensures positionally fixed cell behaviors relative to the invagination point.
• Asymmetric geometrical setup combined with dynamic patterning ensures functional organ formation.