Development and migration of avian sympathetic preganglionic neurons

Area of Science:

• Neuroscience
• Developmental Biology
• Embryology

Background:

• The development of neuronal populations with distinct fates requires understanding their precise migration patterns.
• Avian sympathetic preganglionic neurons, known as Terni column cells, originate in the spinal cord but their developmental migration is not fully understood.

Purpose of the Study:

• To investigate the developmental migration of sympathetic preganglionic neurons (Terni column cells) in the chick embryo spinal cord.
• To compare the migration of Terni column cells with somatic motoneurons.
• To identify potential cues guiding Terni column cell migration.

Main Methods:

• [3H]thymidine autoradiography to determine neuronal birthdating.
• Retrograde labeling using ventral root injections and wheat germ agglutinin-horseradish peroxidase (WGA-HRP).
• Analysis of neuronal positions and morphology at various embryonic stages.

Main Results:

• Terni column neurons are generated between embryonic days 2-4, coinciding with somatic motoneuron genesis.
• Early-born Terni column cells remain in medial positions before initiating dorsal migration around day 5.
• Dorsal migration to the adult position adjacent to the central canal occurs between days 5-8.
• Migration is independent of sympathetic ganglia targets and spinal afferents.

Conclusions:

• Terni column cell migration is distinct from somatic motoneuron migration.
• Local and/or intrinsic cues within the spinal cord likely guide the dorsal migration of Terni column cells.
• This study elucidates a key developmental process in the avian nervous system.