Zebrafish deadly seven functions in neurogenesis.

Area of Science:

• Developmental Biology
• Neuroscience
• Genetics

Background:

• Motor axon outgrowth, neurogenesis, and somitogenesis are crucial developmental processes.
• The deadly seven (des) gene's role in these processes is not fully understood.
• Notch-Delta signaling is implicated in both neurogenesis and somitogenesis.

Purpose of the Study:

• To investigate the function of the deadly seven (des) gene in embryonic development.
• To elucidate the cellular and molecular mechanisms underlying the des mutant phenotype.
• To determine the relationship between des and Notch-Delta signaling in neurogenesis.

Main Methods:

• Genetic screening to identify mutations affecting motor axon outgrowth.
• Complementation tests to confirm allelism with the deadly seven (des) gene.
• Creation of genetic mosaics to assess cell autonomy of defects.
• Analysis of neural crest cell migration and neuronal populations.
• Overexpression of activated Notch to investigate pathway interactions.

Main Results:

• The des mutation causes defects in motor axon outgrowth, neurogenesis, and somitogenesis.
• Motor axon defects are non-cell autonomous.
• Aberrant neural crest cell migration and misplaced dorsal root ganglion neurons were observed.
• Increased numbers of primary motoneurons and specific hindbrain neurons (Mauthner, RoL2, MiD3cm) were found.
• Decreased Rohon-Beard sensory neurons and increased neural crest-derived dorsal root ganglion neurons suggest an equivalence group.
• Overexpressing activated Notch reduced Mauthner cell numbers in des mutants.

Conclusions:

• The deadly seven (des) gene is essential for proper motor axon outgrowth and neurogenesis.
• des functions non-cell autonomously in motor axon development.
• The des gene acts through the Notch-Delta signaling pathway to regulate cell production in the central and peripheral nervous systems.