The study reports the discovery of trunk sympathetic neurons in the sea lamprey, Petromyzon marinus, an extant jawless vertebrate. These neurons arise from sympathoblasts near the dorsal aorta and undergo noradrenergic specification through a transcriptional program homologous to that described in jawed vertebrates (gnathostomes).
The lamprey sympathoblasts populate the extracardiac space and extend along the length of the trunk in bilateral streams, expressing the catecholamine biosynthetic pathway enzymes tyrosine hydroxylase and dopamine β-hydroxylase. Lineage tracing analysis confirmed that these cells derive from the trunk neural crest. RNA sequencing of the isolated ammocoete trunk sympathoblasts revealed gene profiles characteristic of sympathetic neuron function.
This finding challenges the prevailing dogma that sympathetic ganglia are a gnathostome (jawed vertebrate) innovation. Instead, it suggests that a late-developing rudimentary sympathetic nervous system may have been characteristic of the earliest vertebrates, predating the emergence of jaws.
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by Brittany M. ... at www.nature.com 04-17-2024
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