Analysis of classical neurotransmitter markers in tapeworms: Evidence for extensive loss of neurotransmitter pathways. Issue 13 (November 2018)

• Record Type: Journal Article
• Authors: Preza, Matías; Montagne, Jimena; Costábile, Alicia; Iriarte, Andrés; Castillo, Estela; Koziol, Uriel
• Is Part Of: International journal for parasitology. Volume 48:Issue 13(2018)
• Page Start: 979
• Page End: 992
• Publication Date: 2018-11
• Subjects: Neurotransmitter -- Cestode -- Trematode -- Monogenean -- Planarian -- Neuropeptide F; Parasitology -- Periodicals; Parasitology -- Periodicals; Parasitologie -- Périodiques; Parasitology; Periodicals; Electronic journals; 571.999
• DOI: 10.1016/j.ijpara.2018.06.004
• Languages: English
• ISSNs: 0020-7519

Abstract

Graphical abstract: Highlights: Phylogenetic analysis of genes related to neurotransmitter pathways in flatworms was performed. Tapeworms lack canonical dopamine, histamine, octopamine/tyramine and GABA signaling. Neural expression of cholinergic, serotonergic and glutamatergic markers occur in Hymenolepis microstoma . There is neural and non-neural expression of a peptidergic marker in H. microstoma . Abstract: Parasitic flatworms have complex neuromuscular systems that serve important functions in their life cycles. However, our understanding of neurotransmission in parasitic flatworms is limited. Pioneering studies have suggested the presence of several classical neurotransmitter systems, but their molecular components have not been characterized in most cases. Because these components are conserved in bilaterian animals, we searched the genomes of parasitic flatworms for orthologs of genes required for neurotransmitter synthesis, vesicular transport, reuptake, and reception. Our results indicate that tapeworms have lost the genes that are specifically required in other animals for synaptic signaling using the classical neurotransmitters dopamine, tyramine, octopamine, histamine and gamma-aminobutyric acid (GABA). These results imply that these signaling pathways are either absent in these parasites, or that they require completely different molecular components in comparison with other animals. The orthologs of genes related to histaminergic and GABA signaling are also missing in trematodes (although Schistosoma -specific histaminergic receptors have been previously described). In contrast, conserved genes required for glutamatergic, serotonergic and cholinergic signaling could be found in all analyzed flatworms. We analyzed the expression of selected markers of each pathway in the tapeworm Hymenolepis microstoma by whole-mount in situ hybridization. Each marker was specifically expressed in the nervous system, although with different patterns. In addition, we analyzed the expression of proprotein convertase 2 as a marker of peptidergic cells. This gene showed the widest expression in the nervous system, but was also expressed in other tissues, suggesting additional roles of peptidergic signaling in tapeworm development and reproduction.