Morphogenesis in Drosophila requires nonmuscle myosin heavy chain function

Area of Science:

• Developmental Biology
• Cell Biology
• Molecular Genetics

Background:

• Morphogenesis, essential for embryonic development, involves complex cell shape changes and movements.
• Molecular motors play critical roles in cellular processes, but their direct link to morphogenesis has been unclear.

Purpose of the Study:

• To establish the first direct link between a molecular motor and morphogenesis.
• To identify the gene product responsible for the embryonic-lethal 'zipper' mutations in Drosophila.
• To elucidate the role of nonmuscle myosin II in embryonic development.

Main Methods:

• Utilizing reverse genetics to create mutations in the Drosophila nonmuscle myosin II heavy chain gene.
• Allelic analysis to correlate mutations with previously identified 'zipper' mutations.
• Microscopic analysis of cell morphology and myosin localization in wild-type and mutant embryos.

Main Results:

• Mutations in the nonmuscle myosin II heavy chain gene are embryonic-lethal and allelic to 'zipper' mutations.
• Embryos lacking functional myosin II exhibit defects in dorsal closure, head involution, and axon patterning.
• Myosin II is crucial for maintaining cell shape and facilitates cell sheet movement during morphogenesis.

Conclusions:

• Nonmuscle myosin II is the product of the 'zipper' gene and is essential for Drosophila embryonic development.
• Myosin II plays a fundamental role in cell shape maintenance and cell sheet movement during morphogenesis.
• The processes of cell shape change in morphogenesis and cell division are mechanistically related, both requiring myosin.