Assessment and comparison of putative amine receptor complement/diversity in the brain and eyestalk ganglia of the lobster, Homarus americanus

Authors: CHRISTIE, ANDREW - University Of Hawaii; Hull, Joe; DICKINSON, PATSY - Bowdoin College

Submitted to: Invertebrate Neuroscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2020
Publication Date: 3/26/2020
Citation: Christie, A.E., Hull, J.J., Dickinson, P.S. 2020. Assessment and comparison of putative amine receptor complement/diversity in the brain and eyestalk ganglia of the lobster, Homarus americanus. Invertebrate Neuroscience. 20(7). https://doi.org/10.1007/s10158-020-0239-5.
DOI: https://doi.org/10.1007/s10158-020-0239-5

Interpretive Summary: Although decapod crustaceans (eg. American lobster) have long been useful models for determining the basic principles governing rhythmic motor activities, molecular resources for specific decapod nervous tissues has been limited. This dearth of genetic information can be addressed by transcriptomic datasets, which provide snapshots of gene expression within a specific tissue, time point, and/or condition. In this study, transcriptomic datasets generated from lobster brain and eyestalk ganglia specific RNAs were mined for receptors of biogenic amines (dopamine, tyramine, octopamine, serotonin, and histamine), small molecules signals that function as hormonal modulators of physiology and/or behavior. The current study, which extended more limited previous studies, highlights the utility of tissue/region specific datasets and the importance of using a data assembler that preserves sequence variants. The new analyses yielded full-length sequence information for a number of receptors previously reported as fragments, provided evidence for putative variants for many of the receptors, including some variants that were tissue/region assembly-specific, and revealed three putative amine receptors not described previously. Taken collectively, the data presented in this study represent a significant expansion of what is known regarding amine receptor complement and diversity in the lobster nervous system, and thus provide a broader foundation from which to initiate future molecular and physiological studies of aminergic signaling in this and other decapod species.

Technical Abstract: In decapods, dopamine, octopamine, serotonin, and histamine function as locally released/hormonally delivered modulators of physiology/behavior. Although the functional roles played by amines in decapods have been examined extensively, little is known about the identity/diversity of their amine receptors. Recently, a Homarus americanus mixed nervous system transcriptome was used to identify putative neuronal amine receptors in this species. While many receptors were identi'ed, some were fragmentary, and no evidence of splice/other variants was found. Here, the previously predicted proteins were used to search brain- and eyestalk ganglia-speci'c transcriptomes to assess/compare amine receptor complements in these portions of the lobster nervous system. All previously identi'ed receptors were reidenti'ed from the brain and/or eyestalk ganglia transcriptomes, i.e., dopamine alpha-1, beta-1, and alpha-2 (Homam-DAalpha2R) receptors, octopamine alpha (Homam-OctalphaR), beta-1, beta-2, beta-3, beta-4, and octopamine–tyramine (Homam-OTR-I) receptors, serotonin type-1A, type-1B (Homam-5HTR1B), type-2B, and type-7 receptors; and histamine type-1 (Homam-HA1R), type-2, type-3, and type-4 receptors. For many previously partial proteins, full-length receptors were deduced from brain and/or eyestalk ganglia transcripts, i.e., Homam-DAalpha2R, Homam-OctalphaR, Homam-OTR-I, and Homam-5HTR1B. In addition, novel dopamine/ecdysteroid, octopamine alpha-2, and OTR receptors were discovered, the latter, Homam-OTR-II, being a putative paralog of Homam-OTR-I. Finally, evidence for splice/other variants was found for many receptors, including evidence for some being assembly-speci'c, e.g., a brain-speci'c Homam-OTR-I variant and an eyestalk ganglia-speci'c Homam-HA1R variant. To increase con'dence in the transcriptome-derived sequences, a subset of receptors was cloned using RT-PCR. These data complement/augment those reported previously, providing a more complete picture of amine receptor complement/diversity in the lobster nervous system.