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Jeong H, Baran NM, Sun D, Chatterjee P, Layman TS, Balakrishnan CN, Maney DL, Yi SV. Dynamic molecular evolution of a supergene with suppressed recombination in white-throated sparrows. eLife 2022; 11:e79387. [PMID: 36040313 PMCID: PMC9427109 DOI: 10.7554/elife.79387] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Accepted: 08/17/2022] [Indexed: 12/11/2022] Open
Abstract
In white-throated sparrows, two alternative morphs differing in plumage and behavior segregate with a large chromosomal rearrangement. As with sex chromosomes such as the mammalian Y, the rearranged version of chromosome two (ZAL2m) is in a near-constant state of heterozygosity, offering opportunities to investigate both degenerative and selective processes during the early evolutionary stages of 'supergenes.' Here, we generated, synthesized, and analyzed extensive genome-scale data to better understand the forces shaping the evolution of the ZAL2 and ZAL2m chromosomes in this species. We found that features of ZAL2m are consistent with substantially reduced recombination and low levels of degeneration. We also found evidence that selective sweeps took place both on ZAL2m and its standard counterpart, ZAL2, after the rearrangement event. Signatures of positive selection were associated with allelic bias in gene expression, suggesting that antagonistic selection has operated on gene regulation. Finally, we discovered a region exhibiting long-range haplotypes inside the rearrangement on ZAL2m. These haplotypes appear to have been maintained by balancing selection, retaining genetic diversity within the supergene. Together, our analyses illuminate mechanisms contributing to the evolution of a young chromosomal polymorphism, revealing complex selective processes acting concurrently with genetic degeneration to drive the evolution of supergenes.
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Affiliation(s)
- Hyeonsoo Jeong
- School of Biological Sciences, Georgia Institute of TechnologyAtlantaUnited States
| | - Nicole M Baran
- School of Biological Sciences, Georgia Institute of TechnologyAtlantaUnited States
- Department of Psychology, Emory UniversityAtlantaUnited States
- Department of Ecology, Evolution, Marine Biology, University of California, Santa BarbaraSanta BarbaraUnited States
| | - Dan Sun
- School of Biological Sciences, Georgia Institute of TechnologyAtlantaUnited States
- Department of Medicine Huddinge, Karolinska InstitutetStockholmSweden
| | - Paramita Chatterjee
- School of Biological Sciences, Georgia Institute of TechnologyAtlantaUnited States
| | - Thomas S Layman
- School of Biological Sciences, Georgia Institute of TechnologyAtlantaUnited States
| | | | - Donna L Maney
- Department of Psychology, Emory UniversityAtlantaUnited States
| | - Soojin V Yi
- School of Biological Sciences, Georgia Institute of TechnologyAtlantaUnited States
- Department of Ecology, Evolution, Marine Biology, University of California, Santa BarbaraSanta BarbaraUnited States
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2
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Lambert CT, Lichter JB, Perry AN, Castillo SA, Keane B, Cushing BS, Solomon NG. Medial amygdala ERα expression influences monogamous behaviour of male prairie voles in the field. Proc Biol Sci 2021; 288:20210318. [PMID: 34344176 PMCID: PMC8334872 DOI: 10.1098/rspb.2021.0318] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 07/12/2021] [Indexed: 01/08/2023] Open
Abstract
Formation of long-term pair-bonds is a complex process, involving multiple neural circuits and is context- and experience-dependent. While laboratory studies using prairie voles have identified the involvement of several neural mechanisms, efforts to translate these findings into predictable field outcomes have been inconsistent at best. Here we test the hypothesis that inhibition of oestrogen receptor alpha (ERα) in the medial amygdala of male prairie voles would significantly increase the expression of social monogamy in the field. Prairie vole populations of equal sex ratio were established in outdoor enclosures with males bred for high levels of ERα expression and low levels of prosocial behaviour associated with social monogamy. Medial amygdala ERα expression was knocked down in half the males per population. Knockdown males displayed a greater degree of social monogamy in five of the eight behavioural indices assessed. This study demonstrates the robust nature of ERα in playing a critical role in the expression of male social monogamy in a field setting.
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Affiliation(s)
| | | | - Adam N. Perry
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX 79968, USA
| | - Samuel A. Castillo
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX 79968, USA
| | - Brian Keane
- Department of Biological Sciences, Miami University—Regionals, Hamilton, OH 45011, USA
| | - Bruce S. Cushing
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX 79968, USA
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3
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Sun D, Layman TS, Jeong H, Chatterjee P, Grogan K, Merritt JR, Maney DL, Yi SV. Genome-wide variation in DNA methylation linked to developmental stage and chromosomal suppression of recombination in white-throated sparrows. Mol Ecol 2021; 30:3453-3467. [PMID: 33421223 PMCID: PMC8359194 DOI: 10.1111/mec.15793] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Revised: 11/25/2020] [Accepted: 01/04/2021] [Indexed: 12/14/2022]
Abstract
Much of our knowledge on regulatory impacts of DNA methylation has come from laboratory‐bred model organisms, which may not exhibit the full extent of variation found in wild populations. Here, we investigated naturally‐occurring variation in DNA methylation in a wild avian species, the white‐throated sparrow (Zonotrichia albicollis). This species offers exceptional opportunities for studying the link between genetic differentiation and phenotypic traits because of a nonrecombining chromosome pair linked to both plumage and behavioural phenotypes. Using novel single‐nucleotide resolution methylation maps and gene expression data, we show that DNA methylation and the expression of DNA methyltransferases are significantly higher in adults than in nestlings. Genes for which DNA methylation varied between nestlings and adults were implicated in development and cell differentiation and were located throughout the genome. In contrast, differential methylation between plumage morphs was concentrated in the nonrecombining chromosome pair. Interestingly, a large number of CpGs on the nonrecombining chromosome, localized to transposable elements, have undergone dramatic loss of DNA methylation since the split of the ZAL2 and ZAL2m chromosomes. Changes in methylation predicted changes in gene expression for both chromosomes. In summary, we demonstrate changes in genome‐wide DNA methylation that are associated with development and with specific functional categories of genes in white‐throated sparrows. Moreover, we observe substantial DNA methylation reprogramming associated with the suppression of recombination, with implications for genome integrity and gene expression divergence. These results offer an unprecedented view of ongoing epigenetic reprogramming in a wild population. see also the Perspective by Jordan A. Anderson and Jenny Tung.
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Affiliation(s)
- Dan Sun
- School of Biological Sciences, Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA.,Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX, USA
| | - Thomas S Layman
- School of Biological Sciences, Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
| | - Hyeonsoo Jeong
- School of Biological Sciences, Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
| | - Paramita Chatterjee
- School of Biological Sciences, Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
| | - Kathleen Grogan
- Department of Psychology, Emory University, Atlanta, GA, USA
| | | | - Donna L Maney
- Department of Psychology, Emory University, Atlanta, GA, USA
| | - Soojin V Yi
- School of Biological Sciences, Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
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4
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Maney DL, Merritt JR, Prichard MR, Horton BM, Yi SV. Inside the supergene of the bird with four sexes. Horm Behav 2020; 126:104850. [PMID: 32937166 PMCID: PMC7725849 DOI: 10.1016/j.yhbeh.2020.104850] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 09/04/2020] [Accepted: 09/06/2020] [Indexed: 02/07/2023]
Abstract
The white-throated sparrow (Zonotrichia albicollis) offers unique opportunities to understand the adaptive value of supergenes, particularly their role in alternative phenotypes. In this species, alternative plumage morphs segregate with a nonrecombining segment of chromosome 2, which has been called a 'supergene'. The species mates disassortatively with respect to the supergene; that is, each breeding pair consists of one individual with it and one without it. This species has therefore been called the "bird with four sexes". The supergene segregates with a behavioral phenotype; birds with it are more aggressive and less parental than birds without it. Here, we review our efforts to identify the genes inside the supergene that are responsible for the behavioral polymorphism. The gene ESR1, which encodes estrogen receptor α, differs between the morphs and predicts both territorial and parental behavior. Variation in the regulatory regions of ESR1 causes an imbalance in expression of the two alleles, and the degree to which this imbalance favors the supergene allele predicts territorial singing. In heterozygotes, knockdown of ESR1 causes a phenotypic switch, from more aggressive to less aggressive. We recently showed that another gene important for social behavior, vasoactive intestinal peptide (VIP), is differentially expressed between the morphs and predicts territorial singing. We hypothesize that ESR1 and VIP contribute to behavior in a coordinated way and could represent co-adapted alleles. Because the supergene contains more than 1000 individual genes, this species provides rich possibilities for discovering alleles that work together to mediate life-history trade-offs and maximize the fitness of alternative complex phenotypes.
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Affiliation(s)
- Donna L Maney
- Department of Psychology, Emory University, Atlanta, GA, USA.
| | | | | | - Brent M Horton
- Department of Biology, Millersville University, Millersville, PA, USA
| | - Soojin V Yi
- School of Biological Sciences, Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
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5
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Merritt JR, Grogan KE, Zinzow-Kramer WM, Sun D, Ortlund EA, Yi SV, Maney DL. A supergene-linked estrogen receptor drives alternative phenotypes in a polymorphic songbird. Proc Natl Acad Sci U S A 2020; 117:21673-21680. [PMID: 32817554 PMCID: PMC7474689 DOI: 10.1073/pnas.2011347117] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Behavioral evolution relies on genetic changes, yet few behaviors can be traced to specific genetic sequences in vertebrates. Here we provide experimental evidence showing that differentiation of a single gene has contributed to the evolution of divergent behavioral phenotypes in the white-throated sparrow, a common backyard songbird. In this species, a series of chromosomal inversions has formed a supergene that segregates with an aggressive phenotype. The supergene has captured ESR1, the gene that encodes estrogen receptor α (ERα); as a result, this gene is accumulating changes that now distinguish the supergene allele from the standard allele. Our results show that in birds of the more aggressive phenotype, ERα knockdown caused a phenotypic change to that of the less aggressive phenotype. We next showed that in a free-living population, aggression is predicted by allelic imbalance favoring the supergene allele. Finally, we identified cis-regulatory features, both genetic and epigenetic, that explain the allelic imbalance. This work provides a rare illustration of how genotypic divergence has led to behavioral phenotypic divergence in a vertebrate.
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Affiliation(s)
| | | | | | - Dan Sun
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332
| | - Eric A Ortlund
- Department of Biochemistry, Emory University, Atlanta, GA 30322
| | - Soojin V Yi
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332
| | - Donna L Maney
- Department of Psychology, Emory University, Atlanta, GA 30322
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6
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Horton BM, Michael CM, Prichard MR, Maney DL. Vasoactive intestinal peptide as a mediator of the effects of a supergene on social behaviour. Proc Biol Sci 2020; 287:20200196. [PMID: 32259472 PMCID: PMC7209063 DOI: 10.1098/rspb.2020.0196] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 03/13/2020] [Indexed: 12/15/2022] Open
Abstract
Supergenes, or linked groups of alleles that are inherited together, present excellent opportunities to understand gene-behaviour relationships. In white-throated sparrows (Zonotrichia albicollis), a supergene on the second chromosome associates with a more aggressive and less parental phenotype. This supergene includes the gene for vasoactive intestinal peptide (VIP), a neuropeptide known to play a causal role in both aggression and parental behaviour. Here, using a free-living population, we compared the levels of VIP mRNA between birds with and without the supergene. We focused on the anterior hypothalamus and infundibular region, two brain regions containing VIP neurons known to play a causal role in aggression and parental behaviour, respectively. First, we show that the supergene enhances VIP expression in the anterior hypothalamus and that expression positively predicts vocal aggression independently of genotype in both sexes. Next, we show that the supergene reduces VIP expression in the infundibular region, which suggests reduced secretion of prolactin, a pro-parental hormone. Thus, the patterns of VIP expression in these two regions are consistent with the enhanced aggression and reduced parental behaviour of birds with the supergene allele. Our results illustrate mechanisms by which elements of genomic architecture, such as supergenes, can contribute to the evolution of alternative behavioural phenotypes.
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Affiliation(s)
- Brent M. Horton
- Department of Biology, Millersville University, Millersville, PA, USA
- Department of Psychology, Emory University, Atlanta, GA, USA
| | | | | | - Donna L. Maney
- Department of Psychology, Emory University, Atlanta, GA, USA
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7
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Cox RM. Sex steroids as mediators of phenotypic integration, genetic correlations, and evolutionary transitions. Mol Cell Endocrinol 2020; 502:110668. [PMID: 31821857 DOI: 10.1016/j.mce.2019.110668] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2019] [Revised: 11/19/2019] [Accepted: 11/26/2019] [Indexed: 02/06/2023]
Abstract
In recent decades, endocrinologists have increasingly adopted evolutionary methods and perspectives to characterize the evolution of the vertebrate endocrine system and leverage it as a model for developing and testing evolutionary theories. This review summarizes recent research on sex steroids (androgens and estrogens) to illustrate three ways in which a detailed understanding of the molecular and cellular architecture of hormonally mediated gene expression can enhance our understanding of general evolutionary principles. By virtue of their massively pleiotropic effects on the expression of genes and phenotypes, sex steroids and their receptors can (1) structure the patterns of phenotypic variance and covariance that are available to natural selection, (2) alter the underlying genetic correlations that determine a population's evolutionary response to selection, and (3) facilitate evolutionary transitions in fitness-related phenotypes via subtle regulatory shifts in underlying tissues and genes. These principles are illustrated by the author's research on testosterone and sexual dimorphism in lizards, and by recent examples drawn from other vertebrate systems. Mechanistically, these examples call attention to the importance of evolutionary changes in (1) androgen- and estrogen-mediated gene expression, (2) androgen and estrogen receptor expression, and (3) the distribution of androgen and estrogen response elements in target genes throughout the genome. A central theme to emerge from this review is that the rapidly increasing availability of genomic and transcriptomic data from non-model organisms places evolutionary endocrinologist in an excellent position to address the hormonal regulation of the key evolutionary interface between genes and phenotypes.
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Affiliation(s)
- Robert M Cox
- Department of Biology, University of Virginia, Charlottesville, VA, 22904, USA.
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8
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Grogan KE, Horton BM, Hu Y, Maney DL. A chromosomal inversion predicts the expression of sex steroid-related genes in a species with alternative behavioral phenotypes. Mol Cell Endocrinol 2019; 495:110517. [PMID: 31348983 PMCID: PMC6749608 DOI: 10.1016/j.mce.2019.110517] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 07/18/2019] [Accepted: 07/21/2019] [Indexed: 12/13/2022]
Abstract
In white-throated sparrows, a chromosomal rearrangement has led to alternative phenotypes that differ in sex steroid-dependent behaviors. The rearrangement has captured the genes estrogen receptor alpha and 5-alpha reductase, making these genes strong candidates for mediating the behavioral phenotypes. We report here that of the two genes, expression of estrogen receptor alpha mRNA differs between the morphs and predicts behavior to a much greater extent than does expression of 5-alpha reductase mRNA. Differentiation of estrogen receptor alpha, therefore, is likely more important for the behavioral phenotypes. We also found that in some brain regions, the degree to which testosterone treatment affects the expression of steroid-related genes depends strongly on morph. A large morph difference in estrogen receptor alpha mRNA expression in the amygdala appears to be independent of plasma testosterone; this difference persists during the non-breeding season and is detectable in nestlings at post-hatch day seven. The latter result suggests a substrate for organizational effects of hormones during development.
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Affiliation(s)
- Kathleen E Grogan
- Department of Psychology, Emory University, Atlanta, GA, 30322, USA; Departments of Anthropology and Biology, Pennsylvania State University, University Park, PA, 16802, USA
| | - Brent M Horton
- Department of Psychology, Emory University, Atlanta, GA, 30322, USA
| | - Yuchen Hu
- Department of Psychology, Emory University, Atlanta, GA, 30322, USA
| | - Donna L Maney
- Department of Psychology, Emory University, Atlanta, GA, 30322, USA.
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9
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Heimovics SA, Merritt JR, Jalabert C, Ma C, Maney DL, Soma KK. Rapid effects of 17β-estradiol on aggressive behavior in songbirds: Environmental and genetic influences. Horm Behav 2018; 104:41-51. [PMID: 29605636 PMCID: PMC6344317 DOI: 10.1016/j.yhbeh.2018.03.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 03/27/2018] [Accepted: 03/28/2018] [Indexed: 02/06/2023]
Abstract
Contribution to Special Issue on Fast effects of steroids. 17β-estradiol (E2) has numerous rapid effects on the brain and behavior. This review focuses on the rapid effects of E2 on aggression, an important social behavior, in songbirds. First, we highlight the contributions of studies on song sparrows, which reveal that seasonal changes in the environment profoundly influence the capacity of E2 to rapidly alter aggressive behavior. E2 administration to male song sparrows increases aggression within 20 min in the non-breeding season, but not in the breeding season. Furthermore, E2 rapidly modulates several phosphoproteins in the song sparrow brain. In particular, E2 rapidly affects pCREB in the medial preoptic nucleus, in the non-breeding season only. Second, we describe studies of the white-throated sparrow, which reveal how a genetic polymorphism may influence the rapid effects of E2 on aggression. In this species, a chromosomal rearrangement that includes ESR1, which encodes estrogen receptor α (ERα), affects ERα expression in the brain and the ability of E2 to rapidly promote aggression. Third, we summarize studies showing that aggressive interactions rapidly affect levels of E2 and other steroids, both in the blood and in specific brain regions, and the emerging potential for steroid profiling by liquid chromatography tandem mass spectrometry (LC-MS/MS). Such studies of songbirds demonstrate the value of an ethologically informed approach, in order to reveal how steroids act rapidly on the brain to alter naturally-occurring behavior.
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Affiliation(s)
| | | | - Cecilia Jalabert
- University of British Columbia, Department of Zoology, Vancouver, BC, Canada
| | - Chunqi Ma
- University of British Columbia, Department of Psychology, Vancouver, BC, Canada
| | - Donna L Maney
- Emory University, Department of Psychology, Atlanta, GA, USA
| | - Kiran K Soma
- University of British Columbia, Department of Zoology, Vancouver, BC, Canada; University of British Columbia, Department of Psychology, Vancouver, BC, Canada; Djavad Mowafaghian Centre for Brain Health, Canada
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10
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Stetzik L, Ganshevsky D, Lende MN, Roache LE, Musatov S, Cushing BS. Inhibiting ERα expression in the medial amygdala increases prosocial behavior in male meadow voles (Microtus pennsylvanicus). Behav Brain Res 2018; 351:42-48. [PMID: 29859197 DOI: 10.1016/j.bbr.2018.05.035] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 05/25/2018] [Accepted: 05/29/2018] [Indexed: 02/02/2023]
Abstract
This study tested the hypothesis that site-specific estrogen receptor alpha (ERα) expression is a critical factor in the expression of male prosocial behavior and aggression. Previous studies have shown that in the socially monogamous prairie vole (Microtus ochrogaster) low levels of ERα expression, in the medial amygdala (MeA), play an essential role in the expression of high levels of male prosocial behavior and that increasing ERα expression reduced male prosocial behavior. We used an shRNA adeno-associated viral vector to knock down/inhibit ERα in the MeA of the polygynous male meadow vole (M. pennsylvanicus), which displays significantly higher levels of ERα in the MeA than its monogamous relative. Control males were transfected with a luciferase expressing AAV vector. After treatment males participated in three social behavior tests, a same-sex dyadic encounter, an opposite-sex social preference test and an alloparental test. We predicted that decreasing MeA ERα would increase male meadow vole's prosocial behavior and reduce aggression. The results generally supported the hypothesis. Specifically, MeA knockdown males displayed lower levels of defensive aggression during dyadic encounters and increased levels of overall side-x-side physical contact with females during the social preference test, eliminating the partner preference observed in controls. There was no effect on pup interactions, with both treatments expressing low levels of alloparental behavior. Behaviors affected were similar to those in male prairie voles with increased ERα in the BST rather than the MeA, suggesting that relative changes of expression within these nuclei may play a critical role in regulating prosocial behavior.
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Affiliation(s)
- Lucas Stetzik
- Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325, United States; Department of Pharmacology & Therapeutics, College of Medicine, University of Florida, P.O. Box 100267, Gainesville, FL 32610-0267, United States
| | - Denis Ganshevsky
- Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325, United States
| | - Michelle N Lende
- Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325, United States
| | - Laura E Roache
- Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325, United States
| | - Sergei Musatov
- Department of Neurological Surgery, Weill Cornell College of Medicine, New York, NY 10065, United States
| | - Bruce S Cushing
- Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325, United States; Department of Biological Sciences, University of Texas at El Paso, El Paso 79968, United States.
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11
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Grunst AS, Grunst ML, Formica VA, Korody ML, Betuel AM, Barcelo-Serra M, Ford S, Gonser RA, Tuttle EM. Morph-Specific Patterns of Reproductive Senescence: Connections to Discrete Reproductive Strategies. Am Nat 2018; 191:744-755. [PMID: 29750559 DOI: 10.1086/697377] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
How reproductive strategies contribute to patterns of senescence in natural populations remains contentious. We studied reproductive senescence in the dimorphic white-throated sparrow, an excellent species for exploring this issue. Within both sexes the morphs use distinct reproductive strategies, and disassortative pairing by morph results in pair types with distinct parental systems. White morph birds are more colorful and aggressive than tan counterparts, and white males compete for extrapair matings, whereas tan males are more parental. Tan males and white females share parental care equally, whereas white males provide little parental support to tan females. We found morph-specific patterns of reproductive senescence in both sexes. White males exhibited greater reproductive senescence than tan males. This result likely reflects the difficulty of sustaining a highly competitive reproductive strategy as aging progresses rather than high physiological costs of competitiveness, since white males were also long-lived. Moreover, morph was not consistently related to reproductive senescence across the sexes, arguing against especially high costs of the traits associated with white morph identity. Rather, tan females exhibited earlier reproductive senescence than white females and were short-lived, perhaps reflecting the challenges of unsupported motherhood. Results underscore the importance of social dynamics in determining patterns of reproductive senescence.
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12
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Rapid regulatory evolution of a nonrecombining autosome linked to divergent behavioral phenotypes. Proc Natl Acad Sci U S A 2018; 115:2794-2799. [PMID: 29483264 PMCID: PMC5856536 DOI: 10.1073/pnas.1717721115] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In the white-throated sparrow (Zonotrichia albicollis), the second chromosome bears a striking resemblance to sex chromosomes. First, within each breeding pair of birds, one bird is homozygous for the standard arrangement of the chromosome (ZAL2/ZAL2) and its mate is heterozygous for a different version (ZAL2/ZAL2m). Second, recombination is profoundly suppressed between the two versions, leading to genetic differentiation between them. Third, the ZAL2m version is linked with phenotypic traits, such as bright plumage, high aggression, and low parental behavior, which are usually associated with males. These similarities to sex chromosomes suggest that the evolutionary mechanisms that shape sex chromosomes, in particular genetic degeneration of the heterogametic version due to the suppression of recombination, are likely important in this system as well. Here, we investigated patterns of protein sequence evolution and gene expression evolution between the ZAL2 and ZAL2m chromosomes by whole-genome sequencing and transcriptome analyses. Patterns of protein evolution exhibited only weak signals of genetic degeneration, and few genes harbored signatures of positive selection. We found substantial evidence of transcriptome evolution, such as significant expression divergence between ZAL2 and ZAL2m alleles and signatures of dosage compensation for highly expressed genes. These results suggest that, early in the evolution of heteromorphic chromosomes, gene expression divergence and dosage compensation can prevail before large-scale genetic degeneration. Our results show further that suppression of recombination between heteromorphic chromosomes can lead to the evolution of alternative (sex-like) behavioral phenotypes before substantial genetic degeneration.
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13
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Merritt JR, Davis MT, Jalabert C, Libecap TJ, Williams DR, Soma KK, Maney DL. Rapid effects of estradiol on aggression depend on genotype in a species with an estrogen receptor polymorphism. Horm Behav 2018; 98:210-218. [PMID: 29277700 PMCID: PMC5832363 DOI: 10.1016/j.yhbeh.2017.11.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 11/01/2017] [Accepted: 11/21/2017] [Indexed: 11/18/2022]
Abstract
The white-throated sparrow (Zonotrichia albicollis) represents a powerful model in behavioral neuroendocrinology because it occurs in two plumage morphs that differ with respect to steroid-dependent social behaviors. Birds of the white-striped (WS) morph engage in more territorial aggression than do birds of the tan-striped (TS) morph, and the TS birds engage in more parenting behavior. This behavioral polymorphism is caused by a chromosomal inversion that has captured many genes, including estrogen receptor alpha (ERα). In this study, we tested the hypothesis that morph differences in aggression might be explained by differential sensitivity to estradiol (E2). We administered E2 non-invasively to non-breeding white-throated sparrows and quantified aggression toward a conspecific 10 min later. E2 administration rapidly increased aggression in WS birds but not TS birds, consistent with our hypothesis that differential sensitivity to E2 may at least partially explain morph differences in aggression. To query the site of E2 action in the brain, we administered E2 and quantified Egr-1 expression in brain regions in which expression of ERα is known to differ between the morphs. E2 treatment decreased Egr-1 immunoreactivity in nucleus taeniae of the amygdala, but this effect did not depend on morph. Overall, our results support a role for differential effects of E2 on aggression in the two morphs, but more research will be needed to determine the neuroanatomical site of action.
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Affiliation(s)
- Jennifer R Merritt
- Department of Psychology, 36 Eagle Row, Emory University, Atlanta, GA 30322, USA.
| | - Matthew T Davis
- Department of Psychology, 36 Eagle Row, Emory University, Atlanta, GA 30322, USA
| | - Cecilia Jalabert
- Department of Psychology, 2136 West Mall, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Timothy J Libecap
- Department of Psychology, 36 Eagle Row, Emory University, Atlanta, GA 30322, USA
| | - Donald R Williams
- Department of Psychology, 36 Eagle Row, Emory University, Atlanta, GA 30322, USA
| | - Kiran K Soma
- Department of Psychology, 2136 West Mall, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Donna L Maney
- Department of Psychology, 36 Eagle Row, Emory University, Atlanta, GA 30322, USA
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Frankl-Vilches C, Gahr M. Androgen and estrogen sensitivity of bird song: a comparative view on gene regulatory levels. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2018; 204:113-126. [PMID: 29209770 PMCID: PMC5790841 DOI: 10.1007/s00359-017-1236-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 11/02/2017] [Accepted: 11/09/2017] [Indexed: 12/16/2022]
Abstract
Singing of songbirds is sensitive to testosterone and its androgenic and estrogenic metabolites in a species-specific way. The hormonal effects on song pattern are likely mediated by androgen receptors (AR) and estrogen receptor alpha (ERα), ligand activated transcription factors that are expressed in neurons of various areas of the songbirds' vocal control circuit. The distribution of AR in this circuit is rather similar between species while that of ERα is species variant and concerns a key vocal control area, the HVC (proper name). We discuss the regulation of the expression of the cognate AR and ERα and putative splice variants. In particular, we suggest that transcription factor binding sites in the promoter of these receptors differ between bird species. Further, we suggest that AR- and ERα-dependent gene regulation in vocal areas differs between species due to species-specific DNA binding sites of putative target genes that are required for the transcriptional activity of the receptors. We suggest that species differences in the distribution of AR and ERα in vocal areas and in the genomic sensitivity to these receptors contribute to species-specific hormonal regulation of the song.
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Affiliation(s)
- Carolina Frankl-Vilches
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, 82319, Seewiesen, Germany
| | - Manfred Gahr
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, 82319, Seewiesen, Germany.
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15
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Maney DL. Polymorphisms in sex steroid receptors: From gene sequence to behavior. Front Neuroendocrinol 2017; 47:47-65. [PMID: 28705582 PMCID: PMC6312198 DOI: 10.1016/j.yfrne.2017.07.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 07/05/2017] [Accepted: 07/08/2017] [Indexed: 01/09/2023]
Abstract
Sex steroid receptors have received much interest as potential mediators of human behaviors and mental disorders. Candidate gene association studies have identified about 50 genetic variants of androgen and estrogen receptors that correlate with human behavioral phenotypes. Because most of these polymorphisms lie outside coding regions, discerning their effect on receptor function is not straightforward. Thus, although discoveries of associations improve our ability to predict risk, they have not greatly advanced our understanding of underlying mechanisms. This article is intended to serve as a starting point for psychologists and other behavioral biologists to consider potential mechanisms. Here, I review associations between polymorphisms in sex steroid receptors and human behavioral phenotypes. I then consider ways in which genetic variation can affect processes such as mRNA transcription, splicing, and stability. Finally, I suggest ways that hypotheses about mechanism can be tested, for example using in vitro assays and/or animal models.
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Affiliation(s)
- Donna L Maney
- Department of Psychology, 36 Eagle Row, Emory University, Atlanta, GA 30322, USA.
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Zinzow-Kramer WM, Horton BM, McKee CD, Michaud JM, Tharp GK, Thomas JW, Tuttle EM, Yi S, Maney DL. Genes located in a chromosomal inversion are correlated with territorial song in white-throated sparrows. GENES BRAIN AND BEHAVIOR 2015; 14:641-54. [PMID: 26463687 DOI: 10.1111/gbb.12252] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 08/28/2015] [Accepted: 09/09/2015] [Indexed: 01/10/2023]
Abstract
The genome of the white-throated sparrow (Zonotrichia albicollis) contains an inversion polymorphism on chromosome 2 that is linked to predictable variation in a suite of phenotypic traits including plumage color, aggression and parental behavior. Differences in gene expression between the two color morphs, which represent the two common inversion genotypes (ZAL2/ZAL2 and ZAL2/ZAL2(m) ), may therefore advance our understanding of the molecular underpinnings of these phenotypes. To identify genes that are differentially expressed between the two morphs and correlated with behavior, we quantified gene expression and terrirorial aggression, including song, in a population of free-living white-throated sparrows. We analyzed gene expression in two brain regions, the medial amygdala (MeA) and hypothalamus. Both regions are part of a 'social behavior network', which is rich in steroid hormone receptors and previously linked with territorial behavior. Using weighted gene co-expression network analyses, we identified modules of genes that were correlated with both morph and singing behavior. The majority of these genes were located within the inversion, showing the profound effect of the inversion on the expression of genes captured by the rearrangement. These modules were enriched with genes related to retinoic acid signaling and basic cellular functioning. In the MeA, the most prominent pathways were those related to steroid hormone receptor activity. Within these pathways, the only gene encoding such a receptor was ESR1 (estrogen receptor 1), a gene previously shown to predict song rate in this species. The set of candidate genes we identified may mediate the effects of a chromosomal inversion on territorial behavior.
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Affiliation(s)
| | - B M Horton
- Department of Psychology, Emory University, Atlanta, GA
| | - C D McKee
- Department of Psychology, Emory University, Atlanta, GA
| | - J M Michaud
- Department of Psychology, Emory University, Atlanta, GA
| | - G K Tharp
- Yerkes Nonhuman Primate Genomics Core, Emory University, Atlanta, GA
| | - J W Thomas
- NIH Intramural Sequencing Center, National Human Genome Research Institute, NIH, Rockville, MD
| | - E M Tuttle
- Department of Biology, Indiana State University, Terre Haute, IN.,The Center for Genomic Advocacy, Indiana State University, Terre Haute, IN
| | - S Yi
- School of Biology, Georgia Institute of Technology, Atlanta, GA, USA
| | - D L Maney
- Department of Psychology, Emory University, Atlanta, GA
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