Patterned gene expression directs bipolar planar polarity in Drosophila

Area of Science:

• Developmental Biology
• Cell Biology
• Genetics

Background:

• Convergent extension in Drosophila involves polarized cell movements, narrowing the germband along the dorsal-ventral axis and elongating it along the anterior-posterior axis.
• Tissue remodeling during this process relies on precise gene expression patterning along the anterior-posterior axis, perpendicular to cell movement.

Purpose of the Study:

• To investigate how anterior-posterior (A-P) patterning information directs polarized cell movements during Drosophila germband extension.
• To determine the role of pair-rule genes in establishing planar cell polarity and its link to tissue morphogenesis.

Main Methods:

• Analyzing gene expression patterns of even-skipped and runt in Drosophila embryos.
• Investigating the localization of cortical proteins, including nonmuscle myosin II and Bazooka/PAR-3, in intercalating cells.
• Phenotypic analysis of bazooka mutants during germband extension.

Main Results:

• A-P patterning information leads to polarized cortical protein localization in intercalating cells.
• Striped expression of even-skipped and runt genes is necessary and sufficient to orient planar polarity.
• Nonmuscle myosin II localizes to A-P cell borders, while Bazooka/PAR-3 localizes to D-V cell borders.
• Mutations in bazooka disrupt germband extension, highlighting its role in morphogenesis.

Conclusions:

• Spatial patterns of gene expression coordinate planar polarity across cells.
• Localized distribution of proteins like nonmuscle myosin II and Bazooka/PAR-3, directed by gene expression, is crucial for cell movement and tissue remodeling.
• This mechanism links gene expression to the physical processes of embryonic development.