Drosophila MICAL regulates myofilament organization and synaptic structure

Area of Science:

• Neuroscience
• Cell Biology
• Genetics

Background:

• Synaptic terminal size and structure are critical for function.
• Neuromuscular junctions (NMJs) are essential for muscle control.
• The Drosophila mical gene encodes a conserved multi-domain protein.

Purpose of the Study:

• To identify genes involved in Drosophila neuromuscular junction (NMJ) structure.
• To investigate the role of the Drosophila mical gene in synaptic development and muscle organization.

Main Methods:

• Large-scale mutagenesis screen in Drosophila.
• Immunohistochemical staining to analyze muscle filament organization.
• Transgenic expression of interfering RNA (RNAi) to assess MICAL function.
• Ultrastructural analysis of neuromuscular junctions.

Main Results:

• Mutations in Drosophila mical lead to abnormal NMJ structure, including clustered boutons.
• MICAL is crucial for the proper arrangement of actin and myosin filaments within muscles.
• Disorganized myofilaments accumulate beneath the plasma membrane and interfere with synaptic development.
• D-Titin, a proposed sarcomeric organizer, is less affected than contractile elements.

Conclusions:

• MICAL is required in muscles for higher-order myofilament arrangement.
• Disorganized myofilaments in mical mutants likely cause the observed synaptic growth phenotype.
• The filamentous network surrounding synaptic boutons may act as a physical restraint on synaptic branch spreading.