Ionotropic Receptors as a Driving Force behind Human Synapse Establishment

Area of Science:

• Evolutionary biology
• Neuroscience
• Genomics

Background:

• Synaptic neurotransmission underlies nervous system function, but the origin of synapses remains unclear.
• Synaptic orthologs exist in aneural organisms, posing a challenge to understanding synapse evolution.
• The complexity of nervous systems is linked to the evolution of neurotransmission.

Purpose of the Study:

• To investigate the evolutionary history of synaptic gene networks.
• To identify the origins of human neurotransmission genes within a broader eukaryotic context.
• To understand the role of gene emergence in the evolution of nervous systems.

Main Methods:

• Identified the human neurotransmission gene network (321 genes) from key neurotransmitter systems.
• Reconstructed evolutionary scenarios by searching for synaptic orthologs in 476 eukaryotic species.
• Analyzed the timing of gene emergence relative to key ancestral nodes, like the Human-Cnidaria ancestor.

Main Results:

• The human neurotransmission network includes 83 nervous system-exclusive genes.
• A significant emergence of neuroexclusive genes, particularly ionotropic receptors, occurred in the Human-Cnidaria common ancestor.
• Few synaptic genes originated after this common ancestor, and vertebrates show increased synaptic protein abundance.

Conclusions:

• The early emergence of neuroexclusive genes in a common ancestor was likely critical for synapse evolution.
• The complexity of synaptic networks appears to have increased significantly in vertebrates.
• Understanding ancient gene networks provides insights into the fundamental mechanisms of nervous system evolution.