Biology subjects

Phelps, S. M.

Publications and source records attributed to Phelps, S. M..

11 recordsLinked to original sources

bioRxiv2025

Leptin promotes social context-specific increase in advertisement song effort of male Alston's singing mice

Animal display behaviors, such as advertisement songs, are flashy and attention grabbing by necessity. In order to balance the costs and benefits of such signals, individuals must be able to assess both their own energetic state and their social environment. In this study, we investigated the role of leptin, a hormonal signal of high energy balance, in regulating the vocal advertisement display of Alstons singing mouse (Scotinomys teguina). We manipulated perception of energy balance using exogenous leptin, and social environment through acoustic playback, to ask how internal cues of energy availability are integrated with external social cues that promote singing. We found that both song playback and leptin injection promoted increased song effort. In the absence of song playback, leptin altered amplitude modulation in songs, but did not affect song rate. Additionally, we examined hormone and playback effects on non-vocal behaviors and found that leptin may shift physical activity away from cage exploration and toward wheel running. Finally, we found several positive associations between measures related to high song effort. These results demonstrate that male singing mice use both social context and energy balance to govern their investment in advertisement song and that leptin acts as a mediator of this process.

animal behavior and cognition↗

bioRxiv2025

Mechanisms and control of a novel vocalization: the singing mouse song is a whistle that depends on air sac inflation

Identifying variation in vocal morphology and sound production mechanisms is essential to understanding vocal diversity. Rodents provide an ideal system for exploring this variation as they use multiple sound production mechanisms and have novel vocal structures whose morphology varies interspecifically. Here, we describe the laryngeal morphology and identify the sound production mechanism of Alstons singing mouse (Scotinomys teguina), which produce stereotyped songs. We used micro-computed tomography to examine laryngeal morphology and manipulated excised larynges and surgically ablated a laryngeal muscle to determine sound production mechanism and frequency control. Laryngeal manipulations indicated that a whistle mechanism, likely an edge tone or shallow cavity, produces song. Singing mouse whistles are unique compared to other rodents because they rely on the inflation of an enlarged intralaryngeal air sac called the ventral pouch. Whistle frequency can be controlled by ventral pouch inflation, laryngeal airflow, and by cricothyroid muscle action. Cricothyroid ablation inhibited frequency modulation in vivo, suggesting that singing mice use this muscle during singing. Singing mouse laryngeal morphology and vocal mechanism are distinct from other Neotomids; instead of using vocal fold oscillations for loud, long-distance calls and whistles for close-range interactions, singing mice appear to use whistles for distant and close exchanges by inflating their intralaryngeal air sac. Air sacs have evolved repeatedly among vocalizing mammals and our results indicate a new role for these structures in generating sound. Together, our results expand on an emerging story of how biomechanic and morphological variation contributes to vocal diversity.

physiology↗

bioRxiv2024

Female song elicits increased vocal display effort in both sexes of Alston's singing mouse

Acoustic displays are conspicuous behaviors common across diverse animal taxa. They have long been studied in behavioral ecology, evolutionary biology, and neuroscience. Most of these investigations, however, have focused on male display. For species in which both sexes display, correcting this bias will lead to a fuller understanding of the evolution and function of these behaviors. In this study, we investigated the role of vocal advertisement display in female Alstons singing mice (Scotinomys teguina). Singing mice are small muroid rodents of the family Cricetidae, native to high altitude cloud forests of Central America. Females and males both produce elaborate advertisement songs used in mate attraction and intra-sexual competition. Prior studies have largely focused on male behavior, though we recently found that both sexes dramatically increase their rate of singing and song duration in response to playback of conspecific male song. Here, we tested how mice of both sexes adjust their song effort in response to female song playback. Our results show that, like male song, female song elicits robust increases in song effort from both female and male mice. This study reveals additional social contexts that promote high song effort in this species, while raising additional questions about the role of song in communication within and between the sexes.

animal behavior and cognition↗

bioRxiv2023

Sexual coordination in a whole-brain map of prairie-vole pair-bonding

Sexual bonds are central to the social lives of many species, including humans, and monogamous prairie voles have become the predominant model for investigating such attachments. We developed an automated whole-brain mapping pipeline to identify brain circuits underlying pair-bonding behavior. We identified bonding-related c-Fos induction in 68 brain regions clustered in seven major brain-wide neuronal circuits. These circuits include known regulators of bonding, such as the bed nucleus of the stria terminalis, paraventricular hypothalamus, ventral pallidum, and prefrontal cortex. They also include brain regions previously unknown to shape bonding, such as ventromedial hypothalamus, medial preoptic area and the medial amygdala, but that play essential roles in bonding-relevant processes, such as sexual behavior, social reward and territorial aggression. Contrary to some hypotheses, we found that circuits active during mating and bonding were largely sexually monomorphic. Moreover, c-Fos induction across regions was strikingly consistent between members of a pair, with activity best predicted by rates of ejaculation. A novel cluster of regions centered in the amygdala remained coordinated after bonds had formed, suggesting novel substrates for bond maintenance. Our tools and results provide an unprecedented resource for elucidating the networks that translate sexual experience into an enduring bond.

neuroscience↗

bioRxiv2022

The ChlorON Series: Turn-on fluorescent protein sensors for imaging labile chloride in living cells

Beyond its role as the queen electrolyte, chloride can also serve as an allosteric regulator or even a signaling ion. To illuminate this essential anion across such a spectrum of biological processes, researchers have relied on fluorescence imaging with genetically encoded sensors. In large part, these have been derived from the green fluorescent protein found in the jellyfish Aequorea victoria. However, a standalone sensor with a turn-on intensiometric response at physiological pH has yet to be reported. Here, we address this technology gap by building on our discovery of mNeonGreen (mNG) derived from lanYFP found in the cephalochordate Branchiostoma lanceolatum. Targeted engineering of two non-coordinating residues in the chloride binding pocket of mNG unlocks the ChlorON series. In vitro spectroscopy reveals that the binding of chloride tunes the chromophore environment to give rise to the turn-on response. We further showcase how this unique sensing mechanism can be exploited for directly imaging labile chloride in living cells with spatial and temporal resolution, accelerating the path forward for fundamental and translational aspects of chloride biology. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=61 SRC="FIGDIR/small/503807v2_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@36cc4org.highwire.dtl.DTLVardef@d9dccborg.highwire.dtl.DTLVardef@12ec0fforg.highwire.dtl.DTLVardef@80c9db_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2022

De novo assembly and annotation of the singing mouse genome

BackgroundDeveloping genomic resources for a diverse range of species is an important step towards understanding the mechanisms underlying complex traits.Specifically, organisms that exhibit unique, accessible phenotypes-of-interests, allow researchers to address questions that may be ill-suited to traditional model organisms. We sequenced the genome and transcriptome of Alstons singing mouse (Scotinomys teguina), an emerging model for social cognition and vocal communication. In addition to producing advertisement songs used for mate attraction and male-male competition, these rodents are diurnal, live at high-altitudes, and are obligate insectivores, providing opportunities to explore diverse physiological, ecological, and evolutionary questions. ResultsUsing PromethION, Illumina, and PacBio sequencing, we produced an annotated genome and transcriptome, which were validated using gene expression and functional enrichment analyses. To assess the usefulness of our assemblies, we performed single nuclei sequencing on cells of the orofacial motor cortex, a brain region implicated in song coordination, identifying 12 cell types. ConclusionsThese resources will provide the opportunity to identify the molecular basis of complex traits in singing mice as well as to contribute data that can be used for large-scale comparative analyses.

genomics↗

bioRxiv2022

Discovery of a monomeric green fluorescent protein sensor for chloride by structure-guided bioinformatics

Chloride is an essential anion for all forms of life. Beyond electrolyte balance, an increasing body of evidence points to new roles for chloride in normal physiology and disease. Over the last two decades, this understanding has been advanced by chloride-sensitive fluorescent proteins for imaging applications in living cells. To our surprise, these sensors have been primarily engineered from the green fluorescent protein (GFP) found in the jellyfish Aequorea victoria. However, the GFP family has a rich sequence space that could already encode for new sensors with desired properties, thereby minimizing protein engineering efforts and accelerating biological applications. To efficiently sample this space, we present and validate a stepwise bioinformatics strategy focused first on the chloride binding pocket and second on a monomeric oligomerization state. Using this, we identified GFPxm163 from GFPxm found in the jellyfish Aequorea macrodactyla. In vitro characterization shows that the binding of chloride as well as bromide, iodide, and nitrate rapidly tunes the ground state chromophore equilibrium from the phenolate to the phenol state generating a pH-dependent, turn-off fluorescence response. Furthermore, live-cell fluorescence microscopy reveals that GFPxm163 provides a reversible, yet indirect readout of chloride transport via iodide exchange. With this demonstration, we anticipate that the paring of bioinformatics with protein engineering methods will provide an efficient methodology to discover and design new chloride-sensitive fluorescent proteins for cellular applications. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=108 SRC="FIGDIR/small/499230v1_ufig1.gif" ALT="Figure 1"> View larger version (68K): org.highwire.dtl.DTLVardef@9c0daaorg.highwire.dtl.DTLVardef@14553cforg.highwire.dtl.DTLVardef@817107org.highwire.dtl.DTLVardef@23a6ba_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2022

Coupling a Live Cell Directed Evolution Assay with Coevolutionary Landscapes to Engineer an Improved Fluorescent Rhodopsin Chloride Sensor

Our understanding of chloride in biology can be accelerated through the application of fluorescent protein-based sensors in living cells. Laboratory-guided evolution can be used to diversify and identify sensors with specific properties. Recently, we established that the fluorescent proton-pumping rhodopsin wtGR from Gloeobacter violaceus can be converted into a fluorescent sensor for chloride. To unlock this non-natural function, a single point mutation at the Schiff counterion position from D121V was introduced into wtGR fused with cyan fluorescent protein (CFP) resulting in GR1-CFP. Here, we have integrated coevolutionary analysis with directed evolution to understand how the rhodopsin sequence space can be explored and engineered to improve this starting point. We first show how evolutionary couplings are predictive of functional sites in the rhodopsin family and how a fitness metric based on sequence can be used to quantify known proton-pumping activities of GR-CFP variants. Then, we couple this ability to predict potential functional outcomes with a screening and selection assay in live Escherichia coli to reduce the mutational search space of five residues along the proton-pumping pathway in GR1-CFP. This iterative selection process results in GR2-CFP with four additional mutations, E132K, A84K, T125C, and V245I. Finally, bulk, and single fluorescence measurements in live E. coli reveal that GR2-CFP is a reversible, ratiometric fluorescent sensor for extracellular chloride with an improved dynamic range. We anticipate that our framework will be applicable to other systems, providing a more efficient methodology to engineer fluorescent-protein based sensors with desired properties. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=47 SRC="FIGDIR/small/474067v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@1ddb801org.highwire.dtl.DTLVardef@15b4a9corg.highwire.dtl.DTLVardef@7f497corg.highwire.dtl.DTLVardef@b19c5b_HPS_FORMAT_FIGEXP M_FIG C_FIG

synthetic biology↗

bioRxiv2021

Mapping the vocal circuitry of Alston's singing mouse with pseudorabies virus

Vocalizations, like many social displays, are often elaborate, rhythmically structured behaviors that are modulated by a complex combination of cues. Vocal motor patterns require close coordination of neural circuits governing the muscles of the larynx, jaw, and respiratory system. In the elaborate vocalization of Alstons singing mouse (Scotinomys teguina), for example, each note of its rapid, frequency-modulated trill is accompanied by equally rapid modulation of breath and gape. To elucidate the neural circuitry underlying this behavior, we introduced the polysynaptic retrograde neuronal tracer pseudorabies virus (PRV) into the cricothyroid and digastricus muscles, which control frequency modulation and jaw opening respectively. Each virus singly labels ipsilateral motoneurons (nucleus ambiguous for cricothyroid, and motor trigeminal nucleus for digastricus). We find that the two isogenic viruses heavily and bilaterally co-label neurons in the gigantocellular reticular formation, a putative central pattern generator. The viruses also show strong co-labeling in compartments of the midbrain including the ventrolateral periaqueductal grey and the parabrachial nucleus, two structures strongly implicated in vocalizations. In the forebrain, regions important to social cognition and energy balance both exhibit extensive co-labeling. This includes the paraventricular and arcuate nuclei of the hypothalamus, the lateral hypothalamus, preoptic area, extended amygdala, central amygdala, and the bed nucleus of the stria terminalis. Finally, we find doubly labeled neurons in M1 motor cortex previously described as laryngeal, as well as in the prelimbic cortex, which indicate these cortical regions play a role in vocal production. Although we observe some novel patterns of double-labelling, the progress of both viruses is broadly consistent with vertebrate-general patterns of vocal circuitry, as well as with circuit models derived from primate literature.

neuroscience↗

bioRxiv2020

Comparative neurotranscriptomics reveal widespread species differences associated with bonding

BackgroundPair bonding with a reproductive partner is rare among mammals but is an important feature of human social behavior. Decades of research on monogamous prairie voles (Microtus ochrogaster), along with comparative studies using the related non-bonding meadow vole (M. pennsylvanicus), have revealed many of the neural and molecular mechanisms necessary for pair-bond formation in that species. However, these studies have largely focused on just a few neuromodulatory systems. To test the hypothesis that neural gene expression differences underlie differential capacities to bond, we performed RNA-sequencing on tissue from three brain regions important for bonding and other social behaviors across bond-forming prairie voles and non-bonding meadow voles. We examined gene expression in the amygdala, hypothalamus, and combined ventral pallidum/nucleus accumbens in virgins and at three time points after mating to understand species differences in gene expression at baseline, in response to mating, and during bond formation. ResultsWe first identified species and brain region as the factors most strongly associated with gene expression in our samples. Next, we found gene categories related to cell structure, translation and metabolism that differed in expression across species in virgins, as well as categories associated with cell structure, synaptic and neuroendocrine signaling, and transcription and translation that varied among the focal regions in our study. Additionally, we identified genes that were differentially expressed across species after mating in each of our regions of interest. These include genes involved in regulating transcription, neuron structure, and synaptic plasticity. Finally, we identified modules of co-regulated genes that were strongly correlated with brain region in both species, and modules that were correlated with post-mating time points in prairie voles but not meadow voles. ConclusionsThese results reinforce the importance of pre-mating differences that confer the ability to form pair bonds in prairie voles but not promiscuous species such as meadow voles. Gene ontology analysis supports the hypothesis that pair-bond formation involves transcriptional regulation, and changes in neuronal structure. Together, our results expand knowledge of the genes involved in the pair bonding process and open new avenues of research in the molecular mechanisms of bond formation.

neuroscience↗

bioRxiv2020

Genomic heritability of song and condition in wild singing mice

Courtship displays are dramatic examples of complex behaviors that vary within and among species. Evolutionary explanations for this diversity rely upon genetic variation, yet the heritability of complex phenotypes is seldom investigated in the field. Here, we estimate genomic heritability of advertisement song and body condition in a wild population of singing mice. The heritability of song exhibits a systematic pattern, with high heritability for spectral characteristics linked to vocal morphology, intermediate heritability for rhythmic patterns, and lower but significant heritability for measures of motivation, like song length and rate. Physiological measures of condition, like hormonal markers of adiposity, exhibited intermediate heritability. Among singing mice, song rate and body condition have a strong phenotypic correlation; our estimate suggests a comparable genetic correlation that merits further study. Our results illustrate how advances in genomics and quantitative genetics can be integrated in free-living species to address longstanding challenges in behavior and evolution.

evolutionary biology↗