A focal adhesion protein-based mechanochemical checkpoint regulates cleft progression during branching morphogenesis

Area of Science:

• Cell Biology
• Developmental Biology
• Biochemistry

Background:

• Branching morphogenesis is crucial for organ development, with cleft formation being the initial step.
• ROCK1 and nonmuscle myosin II were previously identified as regulators of a mechanochemical checkpoint in cleft progression.
• The precise molecular mechanisms underlying this checkpoint remained to be elucidated.

Purpose of the Study:

• To investigate the role of ROCK-mediated integrin activation and focal adhesion complexes in the mechanochemical checkpoint of branching morphogenesis.
• To determine how inhibition of ROCK1, nonmuscle myosin II, and focal adhesion kinase (FAK) affects cleft progression and associated molecular events.

Main Methods:

• Utilized inhibition of ROCK1, nonmuscle myosin II, and FAK in developing submandibular salivary glands.
• Assessed integrin β1 activation, focal adhesion complex protein localization and activation (including FAK, talin, vinculin).
• Monitored fibronectin assembly and ERK1/2 activation in the cleft region.

Main Results:

• ROCK1 and nonmuscle myosin II inhibition reduced integrin β1 activation and focal adhesion complex formation in the cleft.
• FAK inhibition disrupted focal adhesion protein recruitment, fibronectin assembly, and decreased ERK1/2 activation, halting cleft progression.
• These findings pinpoint integrin signaling and focal adhesion complexes as key components of the mechanochemical checkpoint.

Conclusions:

• ROCK-mediated inside-out integrin signaling establishes a localized mechanochemical checkpoint essential for branching morphogenesis.
• Active FAK-containing focal adhesion complexes are critical for facilitating cleft progression by regulating downstream signaling and matrix assembly.
• This study elucidates a novel molecular mechanism governing organ development through mechanical signaling pathways.