Traip controls mushroom body size by suppressing mitotic defects

Area of Science:

• Neuroscience
• Genetics
• Cell Biology

Background:

• Microcephaly is a neurological condition characterized by an abnormally small brain size and reduced neuron number.
• Mutations in various genes, including those involved in DNA damage repair (DDR), are linked to microcephaly.
• The precise mechanisms by which DDR gene mutations impair brain development remain incompletely understood.

Purpose of the Study:

• To investigate the role of the TRAIP gene in brain development and its connection to microcephaly.
• To characterize the function of the Drosophila TRAIP homolog, nopo (traip), in neural development.

Main Methods:

• Utilized Drosophila melanogaster as a model organism to study the TRAIP homolog (traip).
• Analyzed traip mutants (traip-) for defects in brain structures, specifically the mushroom body (MB).
• Examined neuroblast cell death, chromosome segregation during mitosis, and cell cycle progression in traip mutants.

Main Results:

• traip mutants exhibited smaller mushroom bodies with fewer neurons, mirroring human primary microcephaly.
• Reduced neuron numbers were attributed to premature loss of mushroom body neuroblasts (MB-NBs), partly through caspase-dependent cell death.
• traip- MB-NBs displayed chromosome bridges during anaphase, leading to polyploidy, aneuploidy, and micronuclei formation.

Conclusions:

• TRAIP plays a crucial role in maintaining genomic stability during mitosis by resolving chromosome bridges.
• This function of TRAIP is essential for preventing premature neural stem cell loss and ensuring proper brain size.
• The study highlights TRAIP's role in unloading stalled replication forks during mitosis as a key mechanism suppressing DNA bridges and promoting adequate neuron numbers.