Asare, E. | Search bioRxiv

bioRxiv2025

Neuronal tRNA Modifications in Aplysia californica are Repatterned during Behavioral Habituation

Transfer RNA (tRNA) modifications have been increasingly implicated as post-transcriptional regulators of basic neuronal functions. However, characterizing tRNA modification profiles in specific neural circuits that control well-defined behaviors is notoriously difficult due to the complexity of conventional neurobiological models. Here, we leveraged the numerically simple central nervous system (CNS) of the marine mollusk Aplysia californica to investigate tRNA modification dynamics in functionally identified neurons during habituation of a defensive reflex. We identified and quantified dozens of neuronal tRNA modifications using liquid chromatography-tandem mass spectrometry (LC-MS/MS), revealing characteristic distributions of select small RNA modifications across different neuronal and non-neuronal tissues. Upon behavioral habituation of the siphon-elicited siphon withdrawal reflex (SSWR), we found that tRNA modification profiles in the major ganglion that controls the SSWR were repatterned with predictable, learning-related changes. We discovered a family of anticodon loop modifications including N6-isopentenyladenosine (i6A) and its downstream product, 2-methylthio-N6-isopentenyladenosine (ms2i6A), that displayed a significant increase and trend toward lower levels, respectively. These tRNA modification dynamics occurred independently of changes in expression of their parent tRNAs, illustrating that behavioral habituation alters the activity of tRNA-modifying enzymes. Overall, our work reveals an underexplored link between tRNA modifications and behavioral habituation and provides new insights toward understanding the post-transcriptional mechanisms of learning and memory. One-Sentence SummaryCharacterization of neuronal tRNA modifications during behavioral habituation in Aplysia californica revealed a post-transcriptional mechanism of learning and memory. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=104 SRC="FIGDIR/small/688303v1_ufig1.gif" ALT="Figure 1000"> View larger version (25K): org.highwire.dtl.DTLVardef@48d01forg.highwire.dtl.DTLVardef@57d28eorg.highwire.dtl.DTLVardef@1c0816dorg.highwire.dtl.DTLVardef@1714716_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2018

Extensive recoding of dengue virus type 2 specifically reduces replication in primate cells without gain-of-function in Aedes aegypti mosquitoes

Dengue virus (DENV), an arthropod-borne (\"arbovirus\") virus causing a range of human maladies ranging from self-limiting dengue fever to the life-threatening dengue shock syndrome, proliferates well in two different taxa of the Animal Kingdom, mosquitoes and primates. Unexpectedly, mosquitoes and primates have distinct preferences when expressing their genes by translation, e.g. members of these taxa show taxonomic group-specific intolerance to certain codon pairs. This is called \"codon pair bias\". By necessity, arboviruses evolved to delicately balance this fundamental difference in their ORFs. Using the mosquito-borne human pathogen DENV we have undone the evolutionarily conserved genomic balance in its ORF sequence and specifically shifted the encoding preference away from primates. However, this recoding of DENV raised concerns of gain-of-function, namely whether recoding could inadvertently increase fitness for replication in the arthropod vector. Using mosquito cell cultures and two strains of Aedes aegypti we did not observe any increase in fitness in DENV2 variants codon pair deoptimized for humans. This ability to disrupt and control an arboviruss host preference has great promise towards developing the next generation of synthetic vaccines not only for DENV but for other emerging arboviral pathogens such as chikungunya virus and Zika virus.

microbiology↗