Abstract
Cnidarian nervous systems utilize chemical transmission to transfer signals through synapses and neurons. To date, ample evidence has been accumulated for the participation of neuropeptides, primarily RFamides, in neurotransmission. Yet, it is still not clear if this is the case for the classical fast neurotransmitters such as GABA, Glutamate, Acetylcholine and Monoamines. A large repertoire of cnidarian Fast Neurotransmitter related Genes (FNGs) has been recently identified in the genome of the sea anemone, Nematostella vectensis. In order to test whether FNGs are localized in cnidarian neurons, we characterized the expression patterns of eight Nematostella genes that are closely or distantly related to human central and peripheral nervous systems genes, in adult Nematostella and compared them to the RFamide localization. Our results show common expression patterns for all tested genes, in a single endodermal cell layer. These expressions did not correspond with the RFamide expressing nerve cell network. Following these results we suggest that the tested Nematostella genes may not be directly involved in vertebrate-like fast neurotransmission.
Highlights
The appearance of nerve cells and nerve systems is one of the most important landmarks in animal evolution, as it allowed animals to better sense and respond to their changing environment, improving their overall fitness
Cnidarian nervous systems are based on synaptic transmission [6], where neuro-signals are initiated by sensory cells in response to external cues [7] that get transmitted through nerve cells networks resulting in muscle response [8]
We examined the spatial mRNA expression patterns of Nematostella genes that are closely or distantly related to human neuronal genes that are involved in biosynthesis, transport or degradation of classical non-peptidergic neurotransmitters, and tested whether these genes are localized in the Nematostella nerve/ sensory cells
Summary
The appearance of nerve cells and nerve systems is one of the most important landmarks in animal evolution, as it allowed animals to better sense and respond to their changing environment, improving their overall fitness. Synaptic gene elements have been identified in sponges which are the earliest known living animals that do not possess a functional nervous system [1,2,3,4]. The first appearance of functional nervous systems in animal evolution is attributed to the coelenterates, including the ctenophores (comb jellies) and the cnidarians [5]. Certain cnidarians have centralized nerve structures, the nerve rings, which is present in anthozoans [10,11] and medusozoans [11,12,13,14] including hydrozoans [15]
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