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Leitão A, Gahr M. Babbling opens the sensory phase for imitative vocal learning. Proc Natl Acad Sci U S A 2024; 121:e2312323121. [PMID: 38621117 PMCID: PMC11067029 DOI: 10.1073/pnas.2312323121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 02/07/2024] [Indexed: 04/17/2024] Open
Abstract
Zebra finches, a species of songbirds, learn to sing by creating an auditory template through the memorization of model songs (sensory learning phase) and subsequently translating these perceptual memories into motor skills (sensorimotor learning phase). It has been traditionally believed that babbling in juvenile birds initiates the sensorimotor phase while the sensory phase of song learning precedes the onset of babbling. However, our findings challenge this notion by demonstrating that testosterone-induced premature babbling actually triggers the onset of the sensory learning phase instead. We reveal that juvenile birds must engage in babbling and self-listening to acquire the tutor song as the template. Notably, the sensory learning of the template in songbirds requires motor vocal activity, reflecting the observation that prelinguistic babbling in humans plays a crucial role in auditory learning for language acquisition.
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Affiliation(s)
- Albertine Leitão
- Department of Behavioural Neurobiology, Max Planck Institute for Biological Intelligence, 82319Seewiesen, Germany
| | - Manfred Gahr
- Department of Behavioural Neurobiology, Max Planck Institute for Biological Intelligence, 82319Seewiesen, Germany
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2
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Friedrich SR, Nevue AA, Andrade ALP, Velho TAF, Mello CV. Emergence of sex-specific transcriptomes in a sexually dimorphic brain nucleus. Cell Rep 2022; 40:111152. [PMID: 35926465 PMCID: PMC9385264 DOI: 10.1016/j.celrep.2022.111152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 04/26/2022] [Accepted: 07/12/2022] [Indexed: 11/29/2022] Open
Abstract
We present the transcriptomic changes underlying the development of an extreme neuroanatomical sex difference. The robust nucleus of the arcopallium (RA) is a key component of the songbird vocal motor system. In zebra finch, the RA is initially monomorphic and then atrophies in females but grows up to 7-fold larger in males. Mirroring this divergence, we show here that sex-differential gene expression in the RA expands from hundreds of predominantly sex chromosome Z genes in early development to thousands of predominantly autosomal genes by the time sexual dimorphism asymptotes. Male-specific developmental processes include cell and axonal growth, synapse assembly and activity, and energy metabolism; female-specific processes include cell polarity and differentiation, transcriptional repression, and steroid hormone and immune signaling. Transcription factor binding site analyses support female-biased activation of pro-apoptotic regulatory networks. The extensive and sex-specific transcriptomic reorganization of RA provides insights into potential drivers of sexually dimorphic neurodevelopment.
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Affiliation(s)
- Samantha R Friedrich
- Department of Behavioral Neuroscience, Oregon Health & Science University (OHSU), Portland, OR 97239, USA
| | - Alexander A Nevue
- Department of Behavioral Neuroscience, Oregon Health & Science University (OHSU), Portland, OR 97239, USA
| | - Abraão L P Andrade
- Brain Institute, Federal University of Rio Grande do Norte, Natal, RN 59078-970, Brazil
| | - Tarciso A F Velho
- Brain Institute, Federal University of Rio Grande do Norte, Natal, RN 59078-970, Brazil
| | - Claudio V Mello
- Department of Behavioral Neuroscience, Oregon Health & Science University (OHSU), Portland, OR 97239, USA.
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3
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Gegenhuber B, Tollkuhn J. Signatures of sex: Sex differences in gene expression in the vertebrate brain. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2020; 9:e348. [PMID: 31106965 PMCID: PMC6864223 DOI: 10.1002/wdev.348] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 04/10/2019] [Accepted: 04/22/2019] [Indexed: 12/13/2022]
Abstract
Women and men differ in disease prevalence, symptoms, and progression rates for many psychiatric and neurological disorders. As more preclinical studies include both sexes in experimental design, an increasing number of sex differences in physiology and behavior have been reported. In the brain, sex-typical behaviors are thought to result from sex-specific patterns of neural activity in response to the same sensory stimulus or context. These differential firing patterns likely arise as a consequence of underlying anatomic or molecular sex differences. Accordingly, gene expression in the brains of females and males has been extensively investigated, with the goal of identifying biological pathways that specify or modulate sex differences in brain function. However, there is surprisingly little consensus on sex-biased genes across studies and only a handful of robust candidates have been pursued in the follow-up experiments. Furthermore, it is not known how or when sex-biased gene expression originates, as few studies have been performed in the developing brain. Here we integrate molecular genetic and neural circuit perspectives to provide a conceptual framework of how sex differences in gene expression can arise in the brain. We detail mechanisms of gene regulation by steroid hormones, highlight landmark studies in rodents and humans, identify emerging themes, and offer recommendations for future research. This article is categorized under: Nervous System Development > Vertebrates: General Principles Gene Expression and Transcriptional Hierarchies > Regulatory Mechanisms Gene Expression and Transcriptional Hierarchies > Sex Determination.
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Affiliation(s)
- Bruno Gegenhuber
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York
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4
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Brain-Derived Neurotrophic Factor Has a Transsynaptic Trophic Effect on Neural Activity in an Adult Forebrain Circuit. J Neurosci 2019; 40:1226-1231. [PMID: 31857358 DOI: 10.1523/jneurosci.2375-19.2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 12/02/2019] [Accepted: 12/11/2019] [Indexed: 11/21/2022] Open
Abstract
While hormone-driven plasticity in the adult brain is well studied, the underlying cellular and molecular mechanisms are less well understood. One example of this is seasonal plasticity in the avian brain, where song nuclei exhibit hormonally driven changes in response to changing photoperiod and circulating sex steroid hormones. Hormone receptor activation in song nucleus HVC (proper name) elicits a robust change in activity in target nucleus RA (robust nucleus of the arcopallium), but the molecular signal responsible for this is unknown. This study addressed whether brain-derived neurotrophic factor (BDNF) mediates a transsynaptic effect from HVC to RA in male Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii). In situ hybridization confirmed an increase in BDNF expression in HVC neurons of birds switched to a long-day (LD) photoperiod plus systemically elevated testosterone (T) levels, compared with short-day (SD) conditions. BDNF expression was virtually absent in RA neurons of SD birds, increasing to barely detectable levels in a small subset of cells in LD+T birds. Infusion of BDNF protein adjacent to the RA of SD birds caused an increase in the spontaneous neuron firing rate. Conversely, the infusion of ANA12, a specific antagonist of the tyrosine-related kinase B (TrkB) for BDNF, prevented the increase in RA neuron firing rate in LD+T birds. These results indicate that BDNF is sufficient, and TrkB receptor activation is necessary, for the transsynaptic trophic effect exerted by HVC on RA. The dramatic change in the activity of RA neurons during the breeding season provides a clear example of transsynaptic BDNF effects in the adult brain in a functionally relevant circuit.SIGNIFICANCE STATEMENT Sex steroid hormones drive changes in brain circuits in all vertebrates, both within specific neurons and on their synaptic targets. Such changes can lead to profound changes in behavior, but little is known about the precise molecular mechanisms that underlie this process. We addressed this question in a seasonally breeding songbird and found that the trophic effects of one forebrain song nucleus on its target are mediated transsynaptically by the neurotrophin BDNF. This suggests that, in addition to their role in development, neurotrophins have critical roles in adult brain plasticity.
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5
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Vellema M, Diales Rocha M, Bascones S, Zsebők S, Dreier J, Leitner S, Van der Linden A, Brewer J, Gahr M. Accelerated redevelopment of vocal skills is preceded by lasting reorganization of the song motor circuitry. eLife 2019; 8:43194. [PMID: 31099755 PMCID: PMC6570526 DOI: 10.7554/elife.43194] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 05/16/2019] [Indexed: 01/16/2023] Open
Abstract
Complex motor skills take considerable time and practice to learn. Without continued practice the level of skill performance quickly degrades, posing a problem for the timely utilization of skilled motor behaviors. Here we quantified the recurring development of vocal motor skills and the accompanying changes in synaptic connectivity in the brain of a songbird, while manipulating skill performance by consecutively administrating and withdrawing testosterone. We demonstrate that a songbird with prior singing experience can significantly accelerate the re-acquisition of vocal performance. We further demonstrate that an increase in vocal performance is accompanied by a pronounced synaptic pruning in the forebrain vocal motor area HVC, a reduction that is not reversed when birds stop singing. These results provide evidence that lasting synaptic changes in the motor circuitry are associated with the savings of motor skills, enabling a rapid recovery of motor performance under environmental time constraints.
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Affiliation(s)
- Michiel Vellema
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, Seewiesen, Germany.,Bio Imaging Lab, University of Antwerp, Antwerp, Belgium
| | - Mariana Diales Rocha
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, Seewiesen, Germany
| | - Sabrina Bascones
- Program for Inflammatory and Cardiovascular Disorders, Institut Hospital del Mar d'Investigacions Mèdiques, Barcelona, Spain
| | - Sándor Zsebők
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Budapest, Hungary
| | - Jes Dreier
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Stefan Leitner
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, Seewiesen, Germany
| | | | - Jonathan Brewer
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Manfred Gahr
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, Seewiesen, Germany
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6
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Contreras-Zárate MJ, Day NL, Ormond DR, Borges VF, Tobet S, Gril B, Steeg PS, Cittelly DM. Estradiol induces BDNF/TrkB signaling in triple-negative breast cancer to promote brain metastases. Oncogene 2019; 38:4685-4699. [PMID: 30796353 PMCID: PMC6565485 DOI: 10.1038/s41388-019-0756-z] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 01/10/2019] [Accepted: 01/23/2019] [Indexed: 12/31/2022]
Abstract
Breast cancer brain metastases (BM) affect younger women disproportionally, including those lacking estrogen receptor (ER), progesterone receptor, and HER2 (known as triple-negative breast cancer; TNBC). Previous studies in preclinical models showed that pre-menopausal levels of estradiol (E2) promote TNBC-BM through incompletely understood mechanisms involving reactive astrocytes. Herein, a novel mechanism involving E2-dependent upregulation of brain-derived neurotrophic factor (BDNF) in astrocytes, and subsequent activation of tumor cell tropomyosin kinase receptor B (TrkB), is identified. E2 increased experimental BM of TNBC 4T1BR5 and E0771 cells by 21 and 3.6 fold, respectively, compared to E2-depleted mice. ERα+ reactive astrocytes were found at early and late stages of BM, and E2 upregulated BDNF in ER+ reactive astrocytes in vitro and in vivo. TrkB was expressed in TNBC brain-trophic cell lines, BM-patient-derived xenografts, and breast cancer BM. Conditioned media from E2-treated astrocytes (CM-E2) activated TrkB and downstream AKT, ERK, and PLC-γ signaling in TNBC cells, increasing their invasiveness and tumor-initiating capability in vitro. The promotion of BM by E2-activated astrocytes was found to be more complex, involving feedback loops and other receptor tyrosine kinases. In 4T1BR5 cells, there was a positive feedback loop whereby astrocytic BDNF induced cancer cell BDNF translation. Upregulation of cancer cell BDNF was required to promote full invasiveness of 4T1BR5 in response to CM-E2, and was observed in brain metastatic cells in E2-treated mice in vivo. Moreover, the non-competitive BDNF/TrkB inhibitor ANA-12 reduced E2-induced 4T1BR5 BM to levels similar to OVX mice. BDNF also activated EGFR in TrkB+EGFR+ TNBC cells, suggesting that E2 action through astrocytes activates redundant pathways promoting BM. These findings have important therapeutic implications, as they provide a rationale to use E2-depletion therapies or TrkB inhibitors to prevent or delay development of BM in younger women.
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Affiliation(s)
- Maria J Contreras-Zárate
- Department of Pathology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA
| | - Nicole L Day
- Department of Pathology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA
| | - D Ryan Ormond
- Department of Neurosurgery, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA
| | - Virginia F Borges
- Department of Medicine, Division of Medical Oncology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA
| | - Stuart Tobet
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Brunilde Gril
- Women's Malignancies Branch, National Cancer Institute, Bethesda, MD, USA
| | - Patricia S Steeg
- Women's Malignancies Branch, National Cancer Institute, Bethesda, MD, USA
| | - Diana M Cittelly
- Department of Pathology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO, USA.
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7
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17β-estradiol modulates NGF and BDNF expression through ERβ mediated ERK signaling in cortical astrocytes. Biologia (Bratisl) 2018. [DOI: 10.2478/s11756-018-0099-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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8
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Wermke K, Quast A, Hesse V. From melody to words: The role of sex hormones in early language development. Horm Behav 2018; 104:206-215. [PMID: 29573996 DOI: 10.1016/j.yhbeh.2018.03.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2018] [Revised: 03/16/2018] [Accepted: 03/20/2018] [Indexed: 01/07/2023]
Abstract
Contribution to Special Issue on Fast effects of steroids. Human infants are the most proficient of the few vocal learner species. Sharing similar principles in terms of the generation and modification of complex sounds, cross-vocal learner comparisons are a suitable strategy when it comes to better understanding the evolution and mechanisms of auditory-vocal learning in human infants. This approach will also help us to understand sex differences in relation to vocal development towards language, the underlying brain mechanisms thereof and sex-specific hormonal effects. Although we are still far from being capable of discovering the "fast effects of steroids" in human infants, we have identified that peripheral hormones (blood serum) are important regulators of vocal behaviour towards language during a transitory hormone surge ("mini-puberty") that is comparable in its extent to puberty. This new area of research in human infants provides a promising opportunity to not only better understand early language acquisition from an ontogenetic and phylogenetic perspective, but to also identify reliable clinical risk-markers in infants for the development of later language disorders.
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Affiliation(s)
- Kathleen Wermke
- Center for Prespeech Development & Developmental Disorders, Department of Orthodontics University Hospital of Würzburg, 97070 Würzburg, Germany.
| | - Anja Quast
- Center for Prespeech Development & Developmental Disorders, Department of Orthodontics University Hospital of Würzburg, 97070 Würzburg, Germany; Department of Orthodontics, University Medical Center Goettingen, 37075 Goettingen, Germany
| | - Volker Hesse
- Institute for Experimental Paediatric Endocrinology, Charité-University-Medicine Berlin, 13533 Berlin, Germany
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9
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Brague JC, Lenchur CN, Hayden JM, Davidson RH, Corrigan K, Santini GT, Swann JM. BDNF infusion into the MPN mag is sufficient to restore copulatory behavior in the castrated Syrian hamster. Horm Behav 2018; 102:69-75. [PMID: 29750970 DOI: 10.1016/j.yhbeh.2018.05.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 05/03/2018] [Accepted: 05/06/2018] [Indexed: 11/18/2022]
Abstract
Testosterone plays a key role in the expression of male sex behavior by influencing cellular activity and synapses within the magnocellular medial preoptic nucleus (MPN mag), a sub-nucleus of the medial preoptic area (MPOA) in the Syrian hamster. Although the mechanisms underlying hormonally-induced synaptic plasticity in this region remain elusive, the data suggests that an increase in synaptic density may mediate testosterone's effects on copulation. As brain derived neurotrophic factor (BDNF) plays an integral role in regulating synaptic plasticity and gonadal steroids regulate the levels of BDNF, we hypothesize that BDNF may mediate the effects of gonadal hormones on copulatory behavior. To test this hypothesis, we infused BDNF or controls into the MPN mag of long-term castrates. Our results indicate that BDNF, but not the controls, restored copulatory behavior in castrated male Syrian hamsters. Furthermore, the rise of BDNF expression in the MPOA preceded the rise of synaptophysin following testosterone replacement in castrated males. These data are consistent with our hypothesis, implicating a role for BDNF in mediating testosterone's action on copulation and suggest that the delay in testosterone's restoration of copulation is, in part, due to the delay in the increase of BDNF and synaptophysin.
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Affiliation(s)
- Joe C Brague
- Lsehigh University, Department of Biological Sciences, Iacocca Hall, 111 Research Dr., Bethlehem, PA 18015, United States.
| | - Christine N Lenchur
- Lsehigh University, Department of Biological Sciences, Iacocca Hall, 111 Research Dr., Bethlehem, PA 18015, United States.
| | - Julia M Hayden
- Lsehigh University, Department of Biological Sciences, Iacocca Hall, 111 Research Dr., Bethlehem, PA 18015, United States.
| | - Rachel H Davidson
- Lsehigh University, Department of Biological Sciences, Iacocca Hall, 111 Research Dr., Bethlehem, PA 18015, United States.
| | - Kelly Corrigan
- Lsehigh University, Department of Biological Sciences, Iacocca Hall, 111 Research Dr., Bethlehem, PA 18015, United States.
| | - Garrett T Santini
- Lsehigh University, Department of Biological Sciences, Iacocca Hall, 111 Research Dr., Bethlehem, PA 18015, United States.
| | - Jennifer M Swann
- Lsehigh University, Department of Biological Sciences, Iacocca Hall, 111 Research Dr., Bethlehem, PA 18015, United States.
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10
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Tehrani MA, Veney SL. Intracranial administration of the G-protein coupled estrogen receptor 1 antagonist, G-15, selectively affects dimorphic characteristics of the song system in zebra finches (Taeniopygia guttata). Dev Neurobiol 2018; 78:775-784. [PMID: 29675990 DOI: 10.1002/dneu.22599] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 03/23/2018] [Accepted: 04/13/2018] [Indexed: 12/18/2022]
Abstract
In zebra finches (Taeniopygia guttata), estradiol contributes to sexual differentiation of the song system but the receptor(s) underlying its action are not exactly known. Whereas mRNA and/or protein for nuclear estrogen receptors ERα and ERβ are minimally expressed, G-protein coupled estrogen receptor 1 (GPER1) has a much greater distribution within neural song regions and the syrinx. At present, however, it is unclear if this receptor contributes to dimorphic development of the song system. To test this, the specific GPER1 antagonist, G-15, was intracranially administered to zebra finches for 25 days beginning on the day of hatching. In males, G-15 significantly decreased nuclear volumes of HVC and Area X. It also decreased the muscle fiber sizes of ventralis and dorsalis in the syrinx. In females, G-15 had no effect on measures within the brain, but did increase fiber sizes of both muscle groups. In sum, these data suggest that GPER1 can have selective and opposing influences on dimorphisms within the song system, but since not all features were affected additional factors are likely involved. © 2018 Wiley Periodicals, Inc. Develop Neurobiol, 2018.
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Affiliation(s)
| | - Sean L Veney
- Department of Biological Sciences, University Esplanade, Kent, Ohio, 44242
- School of Biomedical Sciences, Kent State University, Kent, Ohio, 44242
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11
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Drug Targets in Neurotrophin Signaling in the Central and Peripheral Nervous System. Mol Neurobiol 2018; 55:6939-6955. [PMID: 29372544 DOI: 10.1007/s12035-018-0885-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 01/08/2018] [Indexed: 12/12/2022]
Abstract
Neurotrophins are a family of proteins that play an important role in the regulation of the growth, survival, and differentiation of neurons in the central and peripheral nervous system. Neurotrophins were earlier characterized by their role in early development, growth, maintenance, and the plasticity of the nervous system during development, but recent findings also indicate their complex role during normal physiology in both neuronal and non-neuronal tissues. Therefore, it is important to recognize a deficiency in the expression of neurotrophins, a major factor driving the debilitating features of several neurologic and psychiatric diseases/disorders. On the other hand, overexpression of neurotrophins is well known to play a critical role in pathogenesis of chronic pain and afferent sensitization, underlying conditions such as lower urinary tract symptoms (LUTS)/disorders and osteoarthritis. The existence of a redundant receptor system of high-and low-affinity receptors accounts for the diverse, often antagonistic, effects of neurotrophins in neurons and non-neuronal tissues in a spatial and temporal manner. In addition, studies looking at bladder dysfunction because of conditions such as spinal cord injury and diabetes mellitus have found alterations in the levels of these neurotrophins in the bladder, as well as in sensory afferent neurons, which further opens a new avenue for therapeutic targets. In this review, we will discuss the characteristics and roles of key neurotrophins and their involvement in the central and periphery nervous system in both normal and diseased conditions.
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12
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Brague JC, Zinn CR, Granot DY, Feathers CT, Swann JM. TrkB is necessary for male copulatory behavior in the Syrian Hamster (Mesocricetus auratus). Horm Behav 2018; 97:162-169. [PMID: 29092774 DOI: 10.1016/j.yhbeh.2017.10.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 10/23/2017] [Accepted: 10/27/2017] [Indexed: 11/29/2022]
Abstract
The magnocellular medial preoptic nucleus (MPN mag), a subdivision of the medial preoptic area (MPOA), plays a critical role in the regulation of copulation in the male Syrian hamster; in part by mediating the effects of gonadal steroids. For example, ablation of the MPN mag eliminates mating and testosterone placed in the MPN mag restores mating in castrated males. Furthermore, testosterone treatment enhances synaptic density and dendritic spines in the MPN mag. Thus, copulatory behaviors are correlated with increases in synaptic morphology in the MPN mag. As brain derived neurotrophic factor (BDNF) and its receptor, tyrosine receptor kinase-B (TrkB), effect neuronal growth and synaptic plasticity, this study explored the role of TrkB and BDNF in mediating testosterone's effects on the MPN mag and behavior. Testosterone treatment increased BDNF expression and conversely lowered TrkB expression in the MPOA. siRNA-mediated TrkB knockdown in the MPN mag eliminated copulation two-days post injection and the behavior was restored one week later. These data indicate that testosterone influences the expression of BDNF and TrkB in the MPOA and that expression of copulation is dependent on the presence of TrkB. Taken together our findings support a role for TrkB and BDNF in mediating the effects of testosterone on copulatory behavior in the Syrian hamster.
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Affiliation(s)
- Joe C Brague
- Lehigh University, Department of Biological Sciences, Iacocca Hall, 111 Research Dr., Bethlehem, PA 18015, United States..
| | - Clifford R Zinn
- Lehigh University, Department of Biological Sciences, Iacocca Hall, 111 Research Dr., Bethlehem, PA 18015, United States
| | - Dean Y Granot
- Lehigh University, Department of Biological Sciences, Iacocca Hall, 111 Research Dr., Bethlehem, PA 18015, United States
| | - Cameron T Feathers
- Lehigh University, Department of Biological Sciences, Iacocca Hall, 111 Research Dr., Bethlehem, PA 18015, United States
| | - Jennifer M Swann
- Lehigh University, Department of Biological Sciences, Iacocca Hall, 111 Research Dr., Bethlehem, PA 18015, United States..
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13
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Wei YC, Wang SR, Xu XH. Sex differences in brain-derived neurotrophic factor signaling: Functions and implications. J Neurosci Res 2017; 95:336-344. [PMID: 27870405 DOI: 10.1002/jnr.23897] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 07/18/2016] [Accepted: 08/01/2016] [Indexed: 02/03/2023]
Abstract
Brain-derived neurotrophic factor (BDNF) regulates diverse processes such as neuronal survival, differentiation, and plasticity. Accumulating evidence suggests that molecular events that direct sexual differentiation of the brain interact with BDNF signaling pathways. This Mini-Review first examines potential hormonal and epigenetic mechanisms through which sex influences BDNF signaling. We then examine how sex-specific regulation of BDNF signaling supports the development and function of sexually dimorphic neural circuits that underlie male-specific genital reflexes in rats and song production in birds. Finally, we discuss the implications of sex differences in BDNF signaling for gender-biased presentation of neurological and psychiatric diseases such as Alzheimer's disease. Although this Mini-Review focuses on BDNF, we try to convey the general message that sex influences brain functions in complex ways and underscore the requirement for and challenge of expanding research on sex differences in neuroscience. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Yi-Chao Wei
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.,University of the Chinese Academy of Sciences, Beijing, China
| | - Shao-Ran Wang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.,University of the Chinese Academy of Sciences, Beijing, China
| | - Xiao-Hong Xu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
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14
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Sexual dimorphic expression of TrkB, TrkB-T1, and BDNF in the medial preoptic area of the Syrian hamster. Brain Res 2017; 1669:122-125. [PMID: 28606780 DOI: 10.1016/j.brainres.2017.06.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 05/16/2017] [Accepted: 06/06/2017] [Indexed: 12/12/2022]
Abstract
Neurotrophins regulate many aspects of neuronal function and activity. Specifically, the binding of Brain-derived neurotrophic factor (BDNF) to Tyrosine receptor kinase-B (TrkB) or its truncated version, TrkB-T1, can cause growth and differentiation or dominant inhibition of receptor signaling, respectively. There is evidence that these neurotropic effects on nervous tissue, in both the central and peripheral nervous system, behave differently between the sexes. This study used western blots to examine the expression of these neurotrophins in the medial preoptic area (MPOA), a sexually dimorphic region of the hamster brain that controls male sex behavior. We report that TrkB-FL and BDNF show greater expression in male MPOA tissue, when compared to female. On the contrary, TrkB-T1 is expressed in greater abundance in the female MPOA. Our results indicate a clear sexual dimorphism of neurotrophins in the MPOA of the Syrian hamster. Furthermore, the greater expression of TrkB-FL and BDNF in the male MPOA suggests that these neurotrophins could be promoting synaptic growth to facilitate male-typical copulation. In contrast, the greater TrkB-T1 expression in the female MPOA suggests a possible inhibition of synaptic growth, and may contribute to the lack of male-typical copulation. Altogether, our data suggests that neurotrophins may play a larger role sexual differentiation than previously thought.
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Beach LQ, Tang YP, Kerver H, Wade J. Inhibition of TrkB limits development of the zebra finch song system. Brain Res 2016; 1642:467-477. [PMID: 27086969 PMCID: PMC4899271 DOI: 10.1016/j.brainres.2016.04.033] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 04/12/2016] [Accepted: 04/13/2016] [Indexed: 01/19/2023]
Abstract
Large sexual dimorphisms exist in the zebra finch song system. Masculinization may be mediated by both estradiol and expression of one or more Z-genes (males: ZZ; females: ZW). Roles of the Z-gene tyrosine kinase B (TrkB) in HVC in masculinizing both HVC and one of its targets the robust nucleus of the arcopallium (RA), were tested using siRNA administration in juvenile males at two ages (post-hatching days 15-17 or 25-27). Birds were euthanized 10 days later. Potential interactions or additive effects with estradiol were evaluated by treating males with the estrogen synthesis inhibitor fadrozole. Females treated with estradiol were also exposed to the siRNA at the later age. Local inhibition of TrkB in males of both ages reduced the volume of HVC, an effect due to a change in cell number and not cell size. In the older males, in which the treatment spanned the period when the projection from HVC to RA grows, TrkB inhibition reduced the volume of RA and the relative number of cells within it. TrkB siRNA in HVC decreased the volume of and soma size in the RA of females, and the projection from HVC to RA in both sexes. Estradiol in females masculinized various aspects of the song system, and its effect in masculinizing the volume of RA was decreased by TrkB inhibition. However, effects of fadrozole in males were limited. The data indicate that TrkB is involved in masculinizing the song system, but for most measures it probably does not work in concert with E2.
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Affiliation(s)
- Linda Qi Beach
- Neuroscience Program, Michigan State University, East Lansing, MI, USA 48824-1101
- Department of Psychology, Michigan State University, East Lansing, MI, USA 48824-1101
| | - Yu Ping Tang
- Neuroscience Program, Michigan State University, East Lansing, MI, USA 48824-1101
- Department of Psychology, Michigan State University, East Lansing, MI, USA 48824-1101
| | - Halie Kerver
- Neuroscience Program, Michigan State University, East Lansing, MI, USA 48824-1101
| | - Juli Wade
- Neuroscience Program, Michigan State University, East Lansing, MI, USA 48824-1101
- Department of Psychology, Michigan State University, East Lansing, MI, USA 48824-1101
- Department of Integrative Biology Michigan State University, East Lansing, MI, USA 48824-1101
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16
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Wade J. Genetic regulation of sex differences in songbirds and lizards. Philos Trans R Soc Lond B Biol Sci 2016; 371:20150112. [PMID: 26833833 DOI: 10.1098/rstb.2015.0112] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2015] [Indexed: 01/06/2023] Open
Abstract
Sex differences in the morphology of neural and peripheral structures related to reproduction often parallel the frequency of particular behaviours displayed by males and females. In a variety of model organisms, these sex differences are organized in development by gonadal steroids, which also act in adulthood to modulate behavioural expression and in some cases to generate parallel anatomical changes on a seasonal basis. Data collected from diverse species, however, suggest that changes in hormone availability are not sufficient to explain sex and seasonal differences in structure and function. This paper pulls together some of this literature from songbirds and lizards and considers the information in the broader context of taking a comparative approach to investigating genetic mechanisms associated with behavioural neuroendocrinology.
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Affiliation(s)
- Juli Wade
- Departments of Psychology and Integrative Biology, Michigan State University, East Lansing, MI 48824, USA
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17
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Larson TA, Lent KL, Bammler TK, MacDonald JW, Wood WE, Caras ML, Thatra NM, Budzillo A, Perkel DJ, Brenowitz EA. Network analysis of microRNA and mRNA seasonal dynamics in a highly plastic sensorimotor neural circuit. BMC Genomics 2015; 16:905. [PMID: 26545368 PMCID: PMC4636775 DOI: 10.1186/s12864-015-2175-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 10/31/2015] [Indexed: 12/31/2022] Open
Abstract
Background Adult neurogenesis and the incorporation of adult-born neurons into functional circuits requires precise spatiotemporal coordination across molecular networks regulating a wide array of processes, including cell proliferation, apoptosis, neurotrophin signaling, and electrical activity. MicroRNAs (miRs) - short, non-coding RNA sequences that alter gene expression by post-transcriptional inhibition or degradation of mRNA sequences - may be involved in the global coordination of such diverse biological processes. To test the hypothesis that miRs related to adult neurogenesis and related cellular processes are functionally regulated in the nuclei of the avian song control circuit, we used microarray analyses to quantify changes in expression of miRs and predicted target mRNAs in the telencephalic nuclei HVC, the robust nucleus of arcopallium (RA), and the basal ganglia homologue Area X in breeding and nonbreeding Gambel’s white-crowned sparrows (Zonotrichia leucophrys gambelli). Results We identified 46 different miRs that were differentially expressed across seasons in the song nuclei. miR-132 and miR-210 showed the highest differential expression in HVC and Area X, respectively. Analyzing predicted mRNA targets of miR-132 identified 33 candidate target genes that regulate processes including cell cycle control, calcium signaling, and neuregulin signaling in HVC. Likewise, miR-210 was predicted to target 14 mRNAs differentially expressed across seasons that regulate serotonin, GABA, and dopamine receptor signaling and inflammation. Conclusions Our results identify potential miR–mRNA regulatory networks related to adult neurogenesis and provide opportunities to discover novel genetic control of the diverse biological processes and factors related to the functional incorporation of new neurons to the adult brain. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-2175-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Tracy A Larson
- Department of Biology, University of Washington, Seattle, WA, 98195, USA.,Present Address: Basic Sciences Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N, Seattle, WA, 98109, USA
| | - Karin L Lent
- Department of Psychology, University of Washington, Seattle, WA, 98195, USA
| | - Theo K Bammler
- Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA, 98195, USA
| | - James W MacDonald
- Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA, 98195, USA
| | - William E Wood
- Department of Otolaryngology, University of Washington, Seattle, WA, 98195, USA.,Graduate Program in Neuroscience, University of Washington, Seattle, WA, 98195, USA.,Present address: Centre National de la Recherche Scientifique, Laboratoire de Neurophysique et Physiologie, UMR 8119, Université Paris Descartes, 45, rue des Saints Pères, 75006, Paris, France
| | - Melissa L Caras
- Department of Psychology, University of Washington, Seattle, WA, 98195, USA.,Graduate Program in Neuroscience, University of Washington, Seattle, WA, 98195, USA.,Present address: Center for Neural Science, New York University, 4 Washington Place, New York, NY, 10003, USA
| | - Nivretta M Thatra
- Department of Biology, University of Washington, Seattle, WA, 98195, USA.,Department of Psychology, University of Washington, Seattle, WA, 98195, USA
| | - Agata Budzillo
- Department of Otolaryngology, University of Washington, Seattle, WA, 98195, USA.,Graduate Program in Neuroscience, University of Washington, Seattle, WA, 98195, USA
| | - David J Perkel
- Department of Biology, University of Washington, Seattle, WA, 98195, USA.,Department of Otolaryngology, University of Washington, Seattle, WA, 98195, USA
| | - Eliot A Brenowitz
- Department of Biology, University of Washington, Seattle, WA, 98195, USA.
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18
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Abstract
New neurons are added throughout the forebrain of adult birds. The song-control system is a model to investigate the addition of new long-projection neurons to a cortical circuit that regulates song, a learned sensorimotor behavior. Neuroblasts destined for the song nucleus HVC arise in the walls of the lateral ventricle, and wander through the pallium to reach HVC. The survival of new HVC neurons is supported by gonadally secreted testosterone and its downstream effectors including neurotrophins, vascularization, and electrical activity of postsynaptic neurons in nucleus RA (robust nucleus of the arcopallium). In seasonal species, the HVC→RA circuit degenerates in nonbreeding birds, and is reconstructed by the incorporation of new projection neurons in breeding birds. There is a functional linkage between the death of mature HVC neurons and the birth of new neurons. Various hypotheses for the function of adult neurogenesis in the song system can be proposed, but this remains an open question.
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Affiliation(s)
- Eliot A Brenowitz
- Departments of Biology and Psychology, University of Washington, Seattle, Washington 98195
| | - Tracy A Larson
- Departments of Biology and Psychology, University of Washington, Seattle, Washington 98195
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Sexual Differences in Cell Loss during the Post-Hatch Development of Song Control Nuclei in the Bengalese Finch. PLoS One 2015; 10:e0125802. [PMID: 25938674 PMCID: PMC4418719 DOI: 10.1371/journal.pone.0125802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 02/26/2015] [Indexed: 11/21/2022] Open
Abstract
Birdsongs and the regions of their brain that control song exhibit obvious sexual differences. However, the mechanisms underlying these sexual dimorphisms remain unknown. To address this issue, we first examined apoptotic cells labeled with caspase-3 or TUNEL in Bengalese finch song control nuclei - the robust nucleus of the archopallium (RA), the lateral magnocellular nucleus of the anterior nidopallium (LMAN), the high vocal center (HVC) and Area X from post-hatch day (P) 15 to 120. Next, we investigated the expression dynamics of pro-apoptotic (Bid, Bad and Bax) and anti-apoptotic (Bcl-2 and Bcl-xL) genes in the aforementioned nuclei. Our results revealed that the female RA at P45 exhibited marked cell apoptosis, confirmed by low densities of Bcl-xL and Bcl-2. Both the male and female LMAN exhibited apoptotic peaks at P35 and P45, respectively, and the observed cell loss was more extensive in males. A corresponding sharp decrease in the density of Bcl-2 after P35 was observed in both sexes, and a greater density of Bid was noted at P45 in males. In addition, we observed that RA volume and the total number of BDNF-expressing cells decreased significantly after unilateral lesion of the LMAN or HVC (two areas that innervate the RA) and that greater numbers of RA-projecting cells were immunoreactive for BDNF in the LMAN than in the HVC. We reasoned that a decrease in the amount of BDNF transported via HVC afferent fibers might result in an increase in cell apoptosis in the female RA. Our data indicate that cell apoptosis resulting from different pro- and anti-apoptotic agents is involved in generating the differences between male and female song control nuclei.
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20
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Brenowitz EA. Transsynaptic trophic effects of steroid hormones in an avian model of adult brain plasticity. Front Neuroendocrinol 2015; 37:119-28. [PMID: 25285401 PMCID: PMC4385747 DOI: 10.1016/j.yfrne.2014.09.003] [Citation(s) in RCA: 18] [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: 07/10/2014] [Revised: 09/16/2014] [Accepted: 09/22/2014] [Indexed: 12/23/2022]
Abstract
The avian song control system provides an excellent model for studying transsynaptic trophic effects of steroid sex hormones. Seasonal changes in systemic testosterone (T) and its metabolites regulate plasticity of this system. Steroids interact with the neurotrophin brain-derived neurotrophic factor (BDNF) to influence cellular processes of plasticity in nucleus HVC of adult birds, including the addition of newborn neurons. This interaction may also occur transsynpatically; T increases the synthesis of BDNF in HVC, and BDNF protein is then released by HVC neurons on to postsynaptic cells in nucleus RA where it has trophic effects on activity and morphology. Androgen action on RA neurons increases their activity and this has a retrograde trophic effect on the addition of new neurons to HVC. The functional linkage of sex steroids to BDNF may be of adaptive value in regulating the trophic effects of the neurotrophin and coordinating circuit function in reproductively relevant contexts.
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Affiliation(s)
- Eliot A Brenowitz
- Departments of Psychology and Biology, and the Virginia Merrill Bloedel Hearing Research Center, University of Washington, United States.
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21
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Dittrich F, Ramenda C, Grillitsch D, Frankl-Vilches C, Ko MC, Hertel M, Goymann W, ter Maat A, Gahr M. Regulatory mechanisms of testosterone-stimulated song in the sensorimotor nucleus HVC of female songbirds. BMC Neurosci 2014; 15:128. [PMID: 25442096 PMCID: PMC4261767 DOI: 10.1186/s12868-014-0128-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 11/13/2014] [Indexed: 01/04/2023] Open
Abstract
Background In male birds, influence of the sex steroid hormone testosterone and its estrogenic metabolites on seasonal song behavior has been demonstrated for many species. In contrast, female song was only recently recognized to be widespread among songbird species, and to date, sex hormone effects on singing and brain regions controlling song development and production (song control nuclei) have been studied in females almost exclusively using domesticated canaries (Serinus canaria). However, domesticated female canaries hardly sing at all in normal circumstances and exhibit only very weak, if any, song seasonally under the natural photoperiod. By contrast, adult female European robins (Erithacus rubecula) routinely sing during the winter season, a time when they defend feeding territories and show elevated circulating testosterone levels. We therefore used wild female European robins captured in the fall to examine the effects of testosterone administration on song as well as on the anatomy and the transcriptome of the song control nucleus HVC (sic). The results obtained from female robins were compared to outcomes of a similar experiment done in female domesticated canaries. Results Testosterone treatment induced abundant song in female robins. Examination of HVC transcriptomes and histological analyses of song control nuclei showed testosterone-induced differentiation processes related to neuron growth and spacing, angiogenesis and neuron projection morphogenesis. Similar effects were found in female canaries treated with testosterone. In contrast, the expression of genes related to synaptic transmission was not enhanced in the HVC of testosterone treated female robins but was strongly up-regulated in female canaries. A comparison of the testosterone-stimulated transcriptomes indicated that brain-derived neurotrophic factor (BDNF) likely functions as a common mediator of the testosterone effects in HVC. Conclusions Testosterone-induced singing of female robins correlated with cellular differentiation processes in the HVC that were partially similar to those seen in the HVC of testosterone-treated female canaries. Other modes of testosterone action, notably related to synaptic transmission, appeared to be regulated in a more species-specific manner in the female HVC. Divergent effects of testosterone on the HVC of different species might be related to differences between species in regulatory mechanisms of the singing behavior. Electronic supplementary material The online version of this article (doi:10.1186/s12868-014-0128-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Falk Dittrich
- Max Planck Institute for Ornithology, Department of Behavioural Neurobiology, Eberhard-Gwinner Strasse, Haus 6a, Seewiesen, 82319, Germany.
| | - Claudia Ramenda
- Max Planck Institute for Ornithology, Department of Behavioural Neurobiology, Eberhard-Gwinner Strasse, Haus 6a, Seewiesen, 82319, Germany.
| | - Doris Grillitsch
- Max Planck Institute for Ornithology, Department of Behavioural Neurobiology, Eberhard-Gwinner Strasse, Haus 6a, Seewiesen, 82319, Germany.
| | - Carolina Frankl-Vilches
- Max Planck Institute for Ornithology, Department of Behavioural Neurobiology, Eberhard-Gwinner Strasse, Haus 6a, Seewiesen, 82319, Germany.
| | - Meng-Ching Ko
- Max Planck Institute for Ornithology, Department of Behavioural Neurobiology, Eberhard-Gwinner Strasse, Haus 6a, Seewiesen, 82319, Germany.
| | - Moritz Hertel
- Max Planck Institute for Ornithology, Department of Behavioural Neurobiology, Eberhard-Gwinner Strasse, Haus 6a, Seewiesen, 82319, Germany.
| | - Wolfgang Goymann
- Max Planck Institute for Ornithology, Department of Behavioural Neurobiology, Eberhard-Gwinner Strasse, Haus 6a, Seewiesen, 82319, Germany.
| | - Andries ter Maat
- Max Planck Institute for Ornithology, Department of Behavioural Neurobiology, Eberhard-Gwinner Strasse, Haus 6a, Seewiesen, 82319, Germany.
| | - Manfred Gahr
- Max Planck Institute for Ornithology, Department of Behavioural Neurobiology, Eberhard-Gwinner Strasse, Haus 6a, Seewiesen, 82319, Germany.
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22
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Tang YP, Wade J. Tracheosyringeal nerve transection in juvenile male zebra finches decreases BDNF in HVC and RA and the projection between them. Neurosci Lett 2014; 583:26-31. [PMID: 25219377 DOI: 10.1016/j.neulet.2014.09.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 08/27/2014] [Accepted: 09/04/2014] [Indexed: 01/11/2023]
Abstract
This study investigated relationships among disruption of normal vocal learning, brain-derived neurotrophic factor (BDNF), and the morphology of song nuclei in juvenile male zebra finches. The tracheosyringeal nerves were bilaterally transected at post-hatching day 20-25, so that the animals could not properly develop species-typical vocalizations. BDNF protein and the projection from HVC to the robust nucleus of the arcopallium (RA) were quantified during the sensorimotor integration phase of song development. The manipulation decreased the number of BDNF cells in HVC and RA, the volume of these areas defined by BDNF labeling, and the projection from HVC to RA. BDNF was not affected in Area X or the lateral magnocellular nucleus of the anterior nidopallium (LMAN). Thus, inhibition of a bird's ability to practice and/or to hear its own typically developing song specifically diminishes BDNF expression in cortical motor regions required for song production.
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Affiliation(s)
- Yu Ping Tang
- Michigan State University, Department of Psychology, East Lansing, MI 48824, United States; Michigan State University, Neuroscience Program, East Lansing, MI 48824, United States.
| | - Juli Wade
- Michigan State University, Department of Psychology, East Lansing, MI 48824, United States; Michigan State University, Department of Zoology, East Lansing, MI 48824, United States; Michigan State University, Neuroscience Program, East Lansing, MI 48824, United States
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23
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Chen Q, Zhang X, Zhao Y, Zhou X, Sun L, Zeng S, Zuo M, Zhang X. Sexual differences in cell proliferation in the ventricular zone, cell migration and differentiation in the HVC of juvenile Bengalese finch. PLoS One 2014; 9:e97403. [PMID: 24841082 PMCID: PMC4026142 DOI: 10.1371/journal.pone.0097403] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2014] [Accepted: 04/17/2014] [Indexed: 11/18/2022] Open
Abstract
Song control nuclei have distinct sexual differences and thus are an ideal model to address how brain areas are sexually differentiated. Through a combination of histological analysis and electrical lesions, we first identified the ventricle site for HVC progenitor cells. We then found that there were significant sex differences in the cellular proliferation activity in the ventricular zone of the HVC, the number of migrating cells along the radial cells (positive immunoreactions to vimentin) and differentiation towards neurons. Through co-culturing of male and female slices containing the developing HVC in the same well, we found that the male slices could produce diffusible substances to masculinize the female HVC. By adding estrogen, an estrogen antagonist, brain-derived neurotrophic factor (BDNF) or its antibody into the culture medium, separately or in combination, we found that these diffusible substances may include estrogen and BDNF. Finally, we found that 1) estrogen-induced BDNF upregulation could be detected 48 hr after estrogen treatment and could not be blocked by a vascular endothelial growth factor (VEGF) receptor inhibitor and 2) the amount of VEGF mRNA expressed in the developing HVC and its adjacent area did not display any significant sex differences, as did the distribution of VEGF and laminin-expressing endothelial cells in the developing HVC. Because these findings are largely different from previous reports on the adult female HVC, it is suggested that our estrogen-induced BDNF up-regulation and the resultant sexual differentiation might not be mediated by VEGF and endothelial cells, but instead, may result from the direct effects of estrogen on BDNF.
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Affiliation(s)
- Qiong Chen
- Beijing Key Laboratory of Gene Resource and Molecular Development, Beijing Normal University, Beijing, China
- Department of Laboratory Medicine, The Third Affiliated Hospital, Guangzhou Medical University, Guangzhou, China
| | - Xuebo Zhang
- Beijing Key Laboratory of Gene Resource and Molecular Development, Beijing Normal University, Beijing, China
- College of Life Sciences, Hainan Normal University, Haikou, China
| | - Yueliu Zhao
- Beijing Key Laboratory of Gene Resource and Molecular Development, Beijing Normal University, Beijing, China
| | - Xin Zhou
- Beijing Key Laboratory of Gene Resource and Molecular Development, Beijing Normal University, Beijing, China
| | - Lina Sun
- Beijing Key Laboratory of Gene Resource and Molecular Development, Beijing Normal University, Beijing, China
| | - Shaoju Zeng
- Beijing Key Laboratory of Gene Resource and Molecular Development, Beijing Normal University, Beijing, China
| | - Mingxue Zuo
- Beijing Key Laboratory of Gene Resource and Molecular Development, Beijing Normal University, Beijing, China
| | - Xinwen Zhang
- College of Life Sciences, Hainan Normal University, Haikou, China
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24
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Prior NH, Yap KN, Soma KK. Acute and chronic effects of an aromatase inhibitor on pair-maintenance behavior of water-restricted zebra finch pairs. Gen Comp Endocrinol 2014; 196:62-71. [PMID: 24231681 DOI: 10.1016/j.ygcen.2013.10.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 10/06/2013] [Accepted: 10/29/2013] [Indexed: 01/25/2023]
Abstract
Zebra finches are highly social songbirds that maintain life-long monogamous pair-bonds. They rely heavily upon these pair-bonds to survive their ever-changing and unpredictable habitat in the Australian desert. These pair-bonds are maintained via a large repertoire of affiliative behaviors that for most of an individual's life are predominately associated with pair maintenance. Water restriction reduces circulating testosterone levels in male zebra finches and the size of the ovary and oviduct in female zebra finches, but water restriction has little or no effects on pair-maintenance behaviors and local levels of testosterone and estradiol in behaviorally-relevant brain regions. These data suggest that in water-restricted zebra finches, local synthesis of testosterone and estradiol in the brain may support the expression of pair-maintenance behaviors. Here, we directly test whether pair-maintenance behaviors are regulated by estradiol, acting via non-genomic or genomic mechanisms, in water-restricted (i.e., non-breeding) zebra finches. In two experiments, subjects were treated with an aromatase inhibitor (fadrozole) either acutely or chronically, and a variety of pair-maintenance behaviors were quantified. Additionally, we quantified the effect of acute fadrozole treatment on brain and circulating estradiol and testosterone levels. Acute fadrozole administration rapidly decreased estradiol levels in the circulation and brain of males and also rapidly increased testosterone levels in the circulation and brain of both males and females. However, neither the acute nor chronic fadrozole treatment decreased pair-maintenance behaviors. In one case, acute fadrozole treatment promoted affiliation. These data suggest that pair-maintenance behavior in non-breeding zebra finches is not promoted by estradiol acting via either non-genomic or genomic mechanisms.
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Affiliation(s)
- Nora H Prior
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
| | - Kang Nian Yap
- Department of Psychology, University of British Columbia, Vancouver, BC, Canada
| | - Kiran K Soma
- Department of Psychology, University of British Columbia, Vancouver, BC, Canada; Department of Zoology, University of British Columbia, Vancouver, BC, Canada; Graduate Program in Neuroscience, University of British Columbia, Vancouver, BC, Canada; Brain Research Centre, University of British Columbia, Vancouver, BC, Canada
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25
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Dittrich F, Ter Maat A, Jansen RF, Pieneman A, Hertel M, Frankl-Vilches C, Gahr M. Maximized song learning of juvenile male zebra finches following BDNF expression in the HVC. Eur J Neurosci 2013; 38:3338-44. [PMID: 23930698 DOI: 10.1111/ejn.12329] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2013] [Revised: 06/28/2013] [Accepted: 07/02/2013] [Indexed: 01/19/2023]
Abstract
During song learning, vocal patterns are matched to an auditory memory acquired from a tutor, a process involving sensorimotor feedback. Song sensorimotor learning and song production of birds is controlled by a set of interconnected brain nuclei, the song control system. In male zebra finches, the beginning of the sensorimotor phase of song learning parallels an increase of the brain-derived neurotrophic factor (BDNF) in just one part of the song control system, the forebrain nucleus HVC. We report here that transient BDNF-mRNA upregulation in the HVC results in a maximized copying of song syllables. Each treated bird shows motor learning to an extent similar to that of the selected best learners among untreated zebra finches. Because this result was not found following BDNF overexpression in the target areas of HVC within the song system, HVC-anchored mechanisms are limiting sensorimotor vocal learning.
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Affiliation(s)
- Falk Dittrich
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, 82319, Seewiesen, Germany; Department of Developmental and Behavioral Neurobiology, VU University Amsterdam, 1081 HV Amsterdam, The Netherlands
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26
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Tang YP, Wade J. Developmental changes in BDNF protein in the song control nuclei of zebra finches. Neuroscience 2013; 250:578-87. [PMID: 23920158 DOI: 10.1016/j.neuroscience.2013.07.062] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 07/25/2013] [Accepted: 07/27/2013] [Indexed: 12/31/2022]
Abstract
The zebra finch song system provides an excellent model to study the mechanisms underlying the development of sex difference in brain structure and function. Only male zebra finches sing and the brain nuclei controlling song learning and production are considerably larger than in females. Sexual differentiation may in part be regulated by estrogen, but other molecules including neurotrophic factors likely also affect masculinization. Brain derived neurotrophic factor (BDNF) plays a crucial role in numerous aspects of vertebrate brain development and function, including neurogenesis, cell survival, growth of axonal projections, synaptogenesis and processes linked to learning and memory. The current study investigated the expression of BDNF protein in juvenile males and females at four ages, as well as in adults, to begin to evaluate the potential roles of endogenous BDNF in particular stages of structural and functional development of the song system. In both HVC and the robust nucleus of the arcopallium (RA), males had more BDNF+ cells than females. The number of immunopositive cells increased in males and decreased in females as they matured, in a pattern generally consistent with a role for BDNF in sensorimotor integration of song learning. In addition, in HVC (but not RA) the ratio of mature BDNF compared to its precursor proBDNF was greater in adult males than those at post-hatching day 25, indicating a region-specific shift in the relative availability of the two forms. Collectively, the data suggest that changes in BDNF protein expression across development may be associated with song system maturation, particularly during the sensorimotor integration of masculine vocalizations.
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Affiliation(s)
- Y P Tang
- Michigan State University, Department of Psychology, East Lansing, MI 48824, USA; Michigan State University, Neuroscience Program, East Lansing, MI 48824, USA.
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27
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Acharya KD, Veney SL. Sexually dimorphic expression and estradiol mediated up-regulation of a sex-linked ribosomal gene, RPS6, in the zebra finch brain. Dev Neurobiol 2013; 73:599-608. [PMID: 23554148 DOI: 10.1002/dneu.22085] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 03/12/2013] [Accepted: 03/26/2013] [Indexed: 12/24/2022]
Abstract
Sex-linked genes are considered to be a major contributor to neural sex differences in zebra finches. While several candidates have been identified, additional ones are continuously being discovered. Here we report on a novel Z-linked ribosomal gene (rpS6) that is enhanced in the male brain as compared to the female's throughout life. In both sexes, expression of rpS6 is highest at P3 and P8 (just before the onset of morphologically detectable sex differences), decreases around P15, and then remains decreased through adulthood. Analysis of rpS6 mRNA revealed widespread distribution throughout the brain. However, within song regions HVC and RA, mRNA containing cells were greater in males as compared to females. Hormones are also involved in the development of neural dimorphisms, so we additionally investigated whether rpS6 might interact with estradiol (E2 ). An up-regulation of rpS6 gene was observed in both sexes following treatment with E2 and the effect was approximately twice as large in males as compared with females. These data suggest that rpS6 may be involved in sexual differentiation of the zebra finch brain, and that the effect is facilitated by E2 .
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Affiliation(s)
- Kalpana D Acharya
- School of Biomedical Sciences, Kent State University, Kent, OH 44242, USA
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Testosterone modulation of angiogenesis and neurogenesis in the adult songbird brain. Neuroscience 2013; 239:139-48. [PMID: 23291451 DOI: 10.1016/j.neuroscience.2012.12.043] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 12/19/2012] [Accepted: 12/20/2012] [Indexed: 01/17/2023]
Abstract
Throughout life, new neurons arise from the ventricular zone of the adult songbird brain and are recruited to the song control nucleus higher vocal center (HVC), from which they extend projections to its target, nucleus robustus of the arcopallium (RA). This process of ongoing parenchymal neuronal addition and circuit integration is both triggered and modulated by seasonal surges in systemic testosterone. Brain aromatase converts circulating testosterone to estradiol, so that HVC is concurrently exposed to both androgenic and estrogenic stimulation. These two signals cooperate to trigger HVC endothelial cell division and angiogenesis, by inducing the regionally-restricted expression of vascular endothelial growth factor (VEGF), its matrix-releasing protease MMP9, and its endothelial receptor VEGFR2. The expanded HVC microvascular network then secretes the neurotrophic factor BDNF, which in turn supports the recruitment of newly generated neurons. This process is striking for its spatial restriction and hence functional specificity. While androgen receptors are broadly expressed by the nuclei of the vocal control system, estrogen receptor (ERα) expression is largely restricted to HVC and its adjacent mediocaudal neopallium. The geographic overlap of these receptor phenotypes in HVC provides the basis for a regionally-defined set of paracrine interactions between the vascular bed and neuronal progenitor pool that both characterize and distinguish this nucleus. These interactions culminate in the focal attraction of new neurons to the adult HVC, the integration of those neurons into the extant vocal control circuits, and ultimately the acquisition and elaboration of song.
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Ottem EN, Bailey DJ, Jordan CL, Breedlove SM. With a little help from my friends: androgens tap BDNF signaling pathways to alter neural circuits. Neuroscience 2012; 239:124-38. [PMID: 23262234 DOI: 10.1016/j.neuroscience.2012.12.019] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Revised: 12/03/2012] [Accepted: 12/05/2012] [Indexed: 12/20/2022]
Abstract
Gonadal androgens are critical for the development and maintenance of sexually dimorphic regions of the male nervous system, which is critical for male-specific behavior and physiological functioning. In rodents, the motoneurons of the spinal nucleus of the bulbocavernosus (SNB) provide a useful example of a neural system dependent on androgen. Unless rescued by perinatal androgens, the SNB motoneurons will undergo apoptotic cell death. In adulthood, SNB motoneurons remain dependent on androgen, as castration leads to somal atrophy and dendritic retraction. In a second vertebrate model, the zebra finch, androgens are critical for the development of several brain nuclei involved in song production in males. Androgen deprivation during a critical period during postnatal development disrupts song acquisition and dimorphic size-associated nuclei. Mechanisms by which androgens exert masculinizing effects in each model system remain elusive. Recent studies suggest that brain-derived neurotrophic factor (BDNF) may play a role in androgen-dependent masculinization and maintenance of both SNB motoneurons and song nuclei of birds. This review aims to summarize studies demonstrating that BDNF signaling via its tyrosine receptor kinase (TrkB) receptor may work cooperatively with androgens to maintain somal and dendritic morphology of SNB motoneurons. We further describe studies that suggest the cellular origin of BDNF is of particular importance in androgen-dependent regulation of SNB motoneurons. We review evidence that androgens and BDNF may synergistically influence song development and plasticity in bird species. Finally, we provide hypothetical models of mechanisms that may underlie androgen- and BDNF-dependent signaling pathways.
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Affiliation(s)
- E N Ottem
- Department of Biology, Northern Michigan University, Marquette, MI 49855, USA.
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Sex and stress hormone influences on the expression and activity of brain-derived neurotrophic factor. Neuroscience 2012; 239:295-303. [PMID: 23211562 DOI: 10.1016/j.neuroscience.2012.10.073] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 10/30/2012] [Accepted: 10/31/2012] [Indexed: 01/02/2023]
Abstract
The neurotrophin, brain-derived neurotrophic factor (BDNF), is recognized as a key component in the regulation of CNS ontogeny, homeostasis and adult neuroplasticity. The importance of BDNF in CNS development and function is well documented by numerous reports from animal studies linking abnormal BDNF signaling to metabolic disturbances and anxiety or depressive-like behavior. Despite the diverse roles for BDNF in nearly all aspects of CNS physiology, the regulation of BDNF expression, as well as our understanding of the signaling mechanisms associated with this neurotrophin, remains incomplete. However, links between sex hormones such as estradiol and testosterone, as well as endogenous and synthetic glucocorticoids (GCs), have emerged as important mediators of BDNF expression and function. Examples of such regulation include brain region-specific induction of Bdnf mRNA in response to estradiol. Additional studies have also documented regulation of the expression of the high-affinity BDNF receptor Tropomyosin-Related Kinase B by estradiol, thus implicating sex steroids not only in the regulation of BDNF expression, but also in mechanisms of signaling associated with it. In addition to gonadal steroids, further evidence also suggests functional interaction between BDNF and GCs, such as in the regulation of corticotrophin-releasing hormone and other important neuropeptides. In this review, we provide an overview of the roles played by selected sex or stress hormones in the regulation of BDNF expression and signaling in the CNS.
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Campos FL, Cristovão AC, Rocha SM, Fonseca CP, Baltazar G. GDNF contributes to oestrogen-mediated protection of midbrain dopaminergic neurones. J Neuroendocrinol 2012; 24:1386-97. [PMID: 22672424 DOI: 10.1111/j.1365-2826.2012.02348.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Parkinson's disease (PD) is characterised by the preferential loss of dopaminergic neurones from the substantia nigra (SN) that leads to the hallmark motor disturbances. Animal and human studies suggest a beneficial effect of oestrogen to the nigrostriatal system, and the regulation of neurotrophic factor expression by oestrogens has been suggested as a possible mechanism contributing to that neuroprotective effect. The present study was designed to investigate whether the neuroprotection exerted by 17β-oestradiol on nigrostriatal dopaminergic neurones is mediated through the regulation of glial cell line-derived neurotrophic factor (GDNF) expression. Using an in vivo rat model of PD, we were able to confirm the relevance of 17β-oestradiol in defending dopaminergic neurones against 6-hydroxydopamine (6-OHDA) toxicity. 17β-oestradiol, released by micro-osmotic pumps, implanted 10 days before intrastriatal 6-OHDA injection, prevented the loss of dopaminergic neurones induced by 6-OHDA. 17β-oestradiol treatment also promoted an increase in GDNF protein levels both in the SN and striatum. To explore the relevance of GDNF increases to 17β-oestradiol neuroprotection, we analysed, in SN neurone-glia cultures, the effect of GDNF antibody neutralisation and RNA interference-mediated GDNF knockdown. The results showed that both GDNF neutralisation and GDNF silencing abolished the dopaminergic protection provided by 17β-oestradiol against 6-OHDA toxicity. Taken together, these results strongly identify GDNF as an important player in 17β-oestradiol-mediated dopaminergic neuroprotection.
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Affiliation(s)
- F L Campos
- CICS-UBI - Health Sciences Research Centre, Department of Medical Sciences, University of Beira Interior, Covilhã, Portugal
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32
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Testosterone and brain-derived neurotrophic factor interactions in the avian song control system. Neuroscience 2012; 239:115-23. [PMID: 23123886 DOI: 10.1016/j.neuroscience.2012.09.023] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2012] [Revised: 09/07/2012] [Accepted: 09/11/2012] [Indexed: 11/20/2022]
Abstract
Interaction between steroid sex hormones and brain-derived neurotrophic factor (BDNF) is a common feature of vertebrate brain organization. The avian song control system provides an excellent model for studying such interactions in neural circuits that regulate song, a learned sensorimotor behavior that is often sexually dimorphic and restricted to reproductive contexts. Testosterone (T) and its steroid metabolites interact with BDNF during development of the song system and in adult plasticity, including the addition of newborn neurons to the pallial nucleus HVC and seasonal changes in structure and function of these circuits. T and BDNF interact locally within HVC to influence cell proliferation and survival. This interaction may also occur transsynpatically; T increases the synthesis of BDNF in HVC, and BDNF protein is then released on to postsynaptic cells in the robust nucleus of the arcopallium (RA) where it has trophic effects. The interaction between sex steroids and BDNF is an example of molecular exploitation, with the evolutionarily ancient steroid-receptor complex having been captured by the more recently evolved BDNF. The functional linkage of sex steroids to BDNF may be of adaptive value in regulating the trophic effects of the neurotrophin in sexually dimorphic and reproductively relevant contexts.
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17β-estradiol regulates the sexually dimorphic expression of BDNF and TrkB proteins in the song system of juvenile zebra finches. PLoS One 2012; 7:e43687. [PMID: 22952738 PMCID: PMC3432032 DOI: 10.1371/journal.pone.0043687] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Accepted: 07/23/2012] [Indexed: 11/19/2022] Open
Abstract
Mature brain derived neurotrophic factor (BDNF) plays critical roles in development of brain structure and function, including neurogenesis, axon growth, cell survival and processes associated with learning. Expression of this peptide is regulated by estradiol (E2). The zebra finch song system is sexually dimorphic - only males sing and the brain regions controlling song are larger and have more cells in males compared to females. Masculinization of this system is partially mediated by E2, and earlier work suggests that BDNF with its high affinity receptor TrkB may also influence this development. The present study evaluated expression of multiple forms of both BDNF and TrkB in the developing song system in juvenile males and females treated with E2 or a vehicle control. Using immunohistochemistry and Western blot analysis, BDNF was detected across the song nuclei of 25-day-old birds. Westerns allowed the pro- and mature forms of BDNF to be individually identified, and proBDNF to be quantified. Several statistically significant effects of sex existed in both the estimated total number of BDNF+ cells and relative concentration of proBDNF, varying across the regions and methodologies. E2 modulated BDNF expression, although the specific nature of the regulation depended on brain region, sex and the technique used. Similarly, TrkB (both truncated and full-length isoforms) was detected by Western blot in the song system of juveniles of both sexes, and expression was regulated by E2. In the context of earlier research on these molecules in the developing song system, this work provides a critical step in describing specific forms of BDNF and TrkB, and how they can be mediated by sex and E2. As individual isoforms of each can have opposing effects on mechanisms, such as cell survival, it will now be important to investigate in depth their specific functions in song system maturation.
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Acharya KD, Veney SL. Characterization of the G-protein-coupled membrane-bound estrogen receptor GPR30 in the zebra finch brain reveals a sex difference in gene and protein expression. Dev Neurobiol 2012; 72:1433-46. [DOI: 10.1002/dneu.22004] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Revised: 10/17/2011] [Accepted: 12/13/2011] [Indexed: 12/22/2022]
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Seasonal changes in patterns of gene expression in avian song control brain regions. PLoS One 2012; 7:e35119. [PMID: 22529977 PMCID: PMC3329558 DOI: 10.1371/journal.pone.0035119] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Accepted: 03/13/2012] [Indexed: 01/23/2023] Open
Abstract
Photoperiod and hormonal cues drive dramatic seasonal changes in structure and function of the avian song control system. Little is known, however, about the patterns of gene expression associated with seasonal changes. Here we address this issue by altering the hormonal and photoperiodic conditions in seasonally-breeding Gambel's white-crowned sparrows and extracting RNA from the telencephalic song control nuclei HVC and RA across multiple time points that capture different stages of growth and regression. We chose HVC and RA because while both nuclei change in volume across seasons, the cellular mechanisms underlying these changes differ. We thus hypothesized that different genes would be expressed between HVC and RA. We tested this by using the extracted RNA to perform a cDNA microarray hybridization developed by the SoNG initiative. We then validated these results using qRT-PCR. We found that 363 genes varied by more than 1.5 fold (>log2 0.585) in expression in HVC and/or RA. Supporting our hypothesis, only 59 of these 363 genes were found to vary in both nuclei, while 132 gene expression changes were HVC specific and 172 were RA specific. We then assigned many of these genes to functional categories relevant to the different mechanisms underlying seasonal change in HVC and RA, including neurogenesis, apoptosis, cell growth, dendrite arborization and axonal growth, angiogenesis, endocrinology, growth factors, and electrophysiology. This revealed categorical differences in the kinds of genes regulated in HVC and RA. These results show that different molecular programs underlie seasonal changes in HVC and RA, and that gene expression is time specific across different reproductive conditions. Our results provide insights into the complex molecular pathways that underlie adult neural plasticity.
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36
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Petersen SL, Krishnan S, Aggison LK, Intlekofer KA, Moura PJ. Sexual differentiation of the gonadotropin surge release mechanism: a new role for the canonical NfκB signaling pathway. Front Neuroendocrinol 2012; 33:36-44. [PMID: 21741397 DOI: 10.1016/j.yfrne.2011.06.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 06/09/2011] [Accepted: 06/11/2011] [Indexed: 12/30/2022]
Abstract
Sex differences in luteinizing hormone (LH) release patterns are controlled by the hypothalamus, established during the perinatal period and required for fertility. Female mammals exhibit a cyclic surge pattern of LH release, while males show a tonic release pattern. In rodents, the LH surge pattern is dictated by the anteroventral periventricular nucleus (AVPV), an estrogen receptor-rich structure that is larger and more cell-dense in females. Sex differences result from mitochondrial cell death triggered in perinatal males by estradiol derived from aromatization of testosterone. Herein we provide an historical perspective and an update describing evidence that molecules important for cell survival and cell death in the immune system also control these processes in the developing AVPV. We conclude with a new model proposing that development of the female AVPV requires constitutive activation of the Tnfα, Tnf receptor 2, NfκB and Bcl2 pathway that is blocked by induction of Tnf receptor-associated factor 2-inhibiting protein (Traip) in the male.
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Affiliation(s)
- Sandra L Petersen
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA 01003, United States.
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37
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Tang YP, Wade J. Developmental changes in the sexually dimorphic expression of secretory carrier membrane protein 1 and its co-localisation with androgen receptor protein in the zebra finch song system. J Neuroendocrinol 2011; 23:584-90. [PMID: 21518034 PMCID: PMC3117055 DOI: 10.1111/j.1365-2826.2011.02146.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The song system of zebra finches differs dramatically between the sexes in terms of both structure and function. Only males sing and the brain regions regulating the learning and production of this behaviour are far more developed in males than females. Mechanisms regulating sexual differentiation likely include both direct genetic and hormonal processes. Expression of both mRNA and the protein product for secretory carrier membrane protein 1 (SCAMP1), a sex chromosome gene, are increased in the brains of juvenile males compared to females. Here we investigated developmental changes in SCAMP1 containing cells in song nuclei and co-localisation with androgen receptor (AR) protein from post-hatching day 25 through adulthood. Almost all SCAMP1 cells co-expressed AR and approximately half of the AR cells expressed SCAMP1 in the HVC and robust nucleus in the arcopallium (RA) of both sexes and in the Area X of males (which could not be clearly defined in females). In HVC and RA, more single and double-labelled cells were detected in males than females overall, and the sex differences increased as animals matured. The results suggest the potential for interaction of these two proteins in regulating development of brain and/or behaviour.
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Affiliation(s)
- Y P Tang
- Department of Psychology, Michigan State University, Neuroscience Program, East Lansing, MI 48824-1101, USA.
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38
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The genetics of sex differences in brain and behavior. Front Neuroendocrinol 2011; 32:227-46. [PMID: 20951723 PMCID: PMC3030621 DOI: 10.1016/j.yfrne.2010.10.001] [Citation(s) in RCA: 216] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Revised: 10/04/2010] [Accepted: 10/06/2010] [Indexed: 11/22/2022]
Abstract
Biological differences between men and women contribute to many sex-specific illnesses and disorders. Historically, it was argued that such differences were largely, if not exclusively, due to gonadal hormone secretions. However, emerging research has shown that some differences are mediated by mechanisms other than the action of these hormone secretions and in particular by products of genes located on the X and Y chromosomes, which we refer to as direct genetic effects. This paper reviews the evidence for direct genetic effects in behavioral and brain sex differences. We highlight the 'four core genotypes' model and sex differences in the midbrain dopaminergic system, specifically focusing on the role of Sry. We also discuss novel research being done on unique populations including people attracted to the same sex and people with a cross-gender identity. As science continues to advance our understanding of biological sex differences, a new field is emerging that is aimed at better addressing the needs of both sexes: gender-based biology and medicine. Ultimately, the study of the biological basis for sex differences will improve healthcare for both men and women.
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Lehman MN, Ladha Z, Coolen LM, Hileman SM, Connors JM, Goodman RL. Neuronal plasticity and seasonal reproduction in sheep. Eur J Neurosci 2011; 32:2152-64. [PMID: 21143669 DOI: 10.1111/j.1460-9568.2010.07530.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Seasonal reproduction represents a naturally occurring example of functional plasticity in the adult brain as it reflects changes in neuroendocrine pathways controlling gonadotropin-releasing hormone (GnRH) secretion and, in particular, the responsiveness of GnRH neurons to estradiol negative feedback. Structural plasticity within this neural circuitry may, in part, be responsible for seasonal switches in the negative feedback control of GnRH secretion that underlie annual reproductive transitions. We review evidence for structural changes in the circuitry responsible for seasonal inhibition of GnRH secretion in sheep. These include changes in synaptic inputs onto GnRH neurons, as well as onto dopamine neurons in the A15 cell group, a nucleus that plays a key role in estradiol negative feedback. We also present preliminary data suggesting a role for neurotrophins and neurotrophin receptors as an early mechanistic step in the plasticity that accompanies seasonal reproductive transitions in sheep. Finally, we review recent evidence suggesting that kisspeptin cells of the arcuate nucleus constitute a critical intermediary in the control of seasonal reproduction. Although a majority of the data for a role of neuronal plasticity in seasonal reproduction has come from the sheep model, the players and principles are likely to have relevance for reproduction in a wide variety of vertebrates, including humans, and in both health and disease.
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Affiliation(s)
- Michael N Lehman
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, N6A 5C1, Canada.
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40
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41
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Kato M, Okanoya K. Molecular characterization of the song control nucleus HVC in Bengalese finch brain. Brain Res 2010; 1360:56-76. [DOI: 10.1016/j.brainres.2010.09.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Revised: 08/11/2010] [Accepted: 09/07/2010] [Indexed: 12/24/2022]
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Viveros MP, Llorente R, Díaz F, Romero-Zerbo SY, Bermudez-Silva FJ, Rodríguez de Fonseca F, Argente J, Chowen JA. Maternal deprivation has sexually dimorphic long-term effects on hypothalamic cell-turnover, body weight and circulating hormone levels. Horm Behav 2010; 58:808-19. [PMID: 20708008 DOI: 10.1016/j.yhbeh.2010.08.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 08/04/2010] [Accepted: 08/05/2010] [Indexed: 01/05/2023]
Abstract
Maternal deprivation (MD) has numerous outcomes, including modulation of neuroendocrine functions. We previously reported that circulating leptin levels are reduced and hypothalamic cell-turnover is affected during MD, with some of these effects being sexually dimorphic. As leptin modulates the development of hypothalamic circuits involved in metabolic control, we asked whether MD has long-term consequences on body weight, leptin levels and the expression of neuropeptides involved in metabolism. Rats were separated from their mother for 24h starting on postnatal day (PND) 9 and sacrificed at PNDs 13, 35 and 75. In both sexes MD reduced body weight, but only until puberty, while leptin levels were unchanged at PND 35 and significantly reduced at PND 75. Adiponectin levels were also reduced at PND 75 in females, while testosterone levels were reduced in males. At PND 13, MD modulated cell-turnover markers in the hypothalamus of males, but not females and increased nestin, a marker of immature neurons, in both sexes, with males having higher levels than females and a significantly greater rise in response to MD. There was no effect of MD on hypothalamic mRNA levels of the leptin receptor or metabolic neuropeptides or the mRNA levels of leptin and adiponectin in adipose tissue. Thus, MD has long-term effects on the levels of circulating hormones that are not correlated with changes in body weight. Furthermore, these endocrine outcomes are different between males and females, which could be due to the fact that MD may have sexually dimorphic effects on hypothalamic development.
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Affiliation(s)
- María-Paz Viveros
- Department of Physiology (Animal Physiology II), Faculty of Biology, Universidad Complutense, Madrid, Spain
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Wu D, Tang YP, Wade J. Co-localization of sorting nexin 2 and androgen receptor in the song system of juvenile zebra finches. Brain Res 2010; 1343:104-11. [PMID: 20452330 PMCID: PMC2900487 DOI: 10.1016/j.brainres.2010.04.084] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 04/26/2010] [Accepted: 04/27/2010] [Indexed: 02/05/2023]
Abstract
Mechanisms regulating sexual differentiation of the zebra finch song system appear to include both genetic and hormonal factors. Sorting Nexin 2 (SNX2), which is involved in trafficking proteins between cellular membranes, and androgen receptor (AR) mRNA are both increased in song control nuclei of juvenile males compared to females. Here, in situ hybridization for SNX2 and immunohistochemistry for AR were used to evaluate these sexual dimorphisms in more detail. Estimates of the total number of HVC cells expressing SNX2 and AR, individually as well as together, were greater in 25-day-old males compared to females. The densities of these types of cells were generally also increased in males compared to females in HVC and Area X (or the equivalent portion of the medial striatum in females). On average, more than half of the AR+ cells co-expressed SNX2 in both brain regions. The potential, therefore, exists for both AR and SNX2 to be involved in masculinization of these two brain regions. One possibility is that they, either separately or in conjunction, enhance the action of trophic factors within the brain.
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Affiliation(s)
- Di Wu
- Department of Psychology, Michigan State University, East Lansing, MI 48824-1101, USA
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Brain-derived neurotrophic factor signaling in the HVC is required for testosterone-induced song of female canaries. J Neurosci 2010; 29:15511-9. [PMID: 20007475 DOI: 10.1523/jneurosci.2564-09.2009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Testosterone-induced singing in songbirds is thought to involve testosterone-dependent morphological changes that include angiogenesis and neuronal recruitment into the HVC, a central part of the song control circuit. Previous work showed that testosterone induces the production of vascular endothelial growth factor (VEGF) and its receptor (VEGFR2 tyrosine kinase), which in turn leads to an upregulation of brain-derived neurotrophic factor (BDNF) production in HVC endothelial cells. Here we report for the first time that systemic inhibition of the VEGFR2 tyrosine kinase is sufficient to block testosterone-induced song in adult female canaries, despite sustained androgen exposure and the persistence of the effects of testosterone on HVC morphology. Expression of exogenous BDNF in HVC, induced locally by in situ transfection, reversed the VEGFR2 inhibition-mediated blockade of song development, thereby restoring the behavioral phenotype associated with androgen-induced song. The VEGFR2-inhibited, BDNF-treated females developed elaborate male-like song that included large syllable repertoires and high syllable repetition rates, features known to attract females. Importantly, although functionally competent new neurons were recruited to HVC after testosterone treatment, the time course of neuronal addition appeared to follow BDNF-induced song development. These findings indicate that testosterone-associated VEGFR2 activity is required for androgen-induced song in adult songbirds and that the behavioral effects of VEGFR2 inhibition can be rescued by BDNF within the adult HVC.
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Abstract
The avian song control system undergoes pronounced seasonal plasticity in response to photoperiod and hormonal cues. The action of testosterone (T) and its metabolites in the song nucleus HVC is both necessary and sufficient to promote breeding season-like growth of its efferent nuclei RA (robust nucleus of the arcopallium) and Area X, suggesting that HVC may release a trophic factor such as brain-derived neurotrophic factor (BDNF) into RA and X. BDNF is involved in many forms of adult neural plasticity in other systems and is present in the avian song system. We used a combination of in situ hybridization and intracerebral infusions to test whether BDNF plays a role in the seasonal-like growth of the song system in adult male white-crowned sparrows. BDNF mRNA levels increased in HVC in response to breeding conditions, and BDNF infusion into RA was sufficient to promote breeding-like changes in somatic area and neuronal density. Expression of the mRNA for the Trk B receptor of BDNF, however, did not vary with seasonal conditions in either HVC or RA. Local blockade of BDNF activity in RA via infusion of Trk-Fc fusion proteins inhibited the response to breeding conditions. Our results indicate that BDNF is sufficient to promote the seasonal plasticity in somatic area and cell density in RA, although NT-3 may also contribute to this process, and suggest that HVC may be a presynaptic source of increased levels of BDNF in RA of breeding-condition birds.
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Paunio T, Korhonen T, Hublin C, Partinen M, Kivimäki M, Koskenvuo M, Kaprio J. Longitudinal study on poor sleep and life dissatisfaction in a nationwide cohort of twins. Am J Epidemiol 2009; 169:206-13. [PMID: 19015202 DOI: 10.1093/aje/kwn305] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Life satisfaction and quality of sleep are important, related components of subjective well-being and general health. However, no earlier investigation is known to have tested the direction of the temporal relation between poor sleep and diminished life satisfaction, including simultaneous examination of shared genetic influences. These features were examined in the present study of a nationwide cohort of 18,631 same-sex Finnish twins with repeated measurements of life satisfaction, sleep quality, and several potential confounders within an interval of 6 years (1975 and 1981). Most individuals (59%) with new-onset life dissatisfaction had experienced suboptimal sleep at baseline. Poor sleep predicted a consistent pattern of life dissatisfaction (odds ratio = 2.1, 95% confidence interval: 1.7, 2.7 from logistic regression on individuals; odds ratio = 3.0, 95% confidence interval: 1.7, 5.3 from conditional logistic regression on twin pairs discordant for life dissatisfaction), whereas life dissatisfaction did not consistently predict poor sleep. There was substantial heritability for both traits, but their shared genetic component was relatively weak, as indicated by genetic correlations of 0.21 for men and 0.27 for women in a multivariate genetic model. This finding is consistent with the hypothesis that poor sleep may have direct effects on the brain, emotions, and mood.
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Affiliation(s)
- Tiina Paunio
- Department of Molecular Medicine, National Public Health Institute, Helsinki, Finland.
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Grisham W, Lee J, Park SH, Mankowski JL, Arnold AP. A dose-response study of estradiol's effects on the developing zebra finch song system. Neurosci Lett 2008; 445:158-61. [PMID: 18790009 DOI: 10.1016/j.neulet.2008.09.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Revised: 08/30/2008] [Accepted: 09/03/2008] [Indexed: 11/25/2022]
Abstract
To gauge the sensitivity of the female zebra finch song system to estradiol (E2), we used subcutaneous implants to administer various doses of E2 to hatchling female zebra finches. Four different doses of E2 were administered: 50, 15, 5 and 0-microg via subcutaneous silicon "ropes" at hatching, and the brains were examined in adulthood. Further, we examined whether masculinization was all-or-none once a threshold was reached or if the morphology of the song system would show a graded response to the various doses of E2. Finally, we asked if the various dependent measures - volume of song nuclei, neuron size, and neuron number - would show differential sensitivity to E2. Fifteen micrograms was sufficient to masculinize many aspects of the song system and was often as effective as 50-microg, causing a dramatic difference relative to the 0-microg group. Different aspects of the song system seemed differentially sensitive to the effects of E2: volumes of song control nuclei, the size of RA neurons, and the number of HVC neurons were significantly masculinized by 15-microg E2, but the number of RA neurons and HVC and lMAN soma sizes required 50-microg. The results suggest that several developmental processes are influenced by E2, possibly because of multiple sites of action or multiple processes that respond to E2.
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Affiliation(s)
- William Grisham
- Department of Psychology and Laboratory of Neuroendocrinology of the Brain Research Institute, University of California, UCLA, 1285 Franz Hall, P.O. Box 951563, Los Angeles, CA 90095-1563, United States.
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Gahr M, Metzdorf R, Schmidl D, Wickler W. Bi-directional sexual dimorphisms of the song control nucleus HVC in a songbird with unison song. PLoS One 2008; 3:e3073. [PMID: 18728787 PMCID: PMC2518117 DOI: 10.1371/journal.pone.0003073] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2008] [Accepted: 07/28/2008] [Indexed: 12/23/2022] Open
Abstract
Sexually dimorphic anatomy of brain areas is thought to be causally linked to sex differences in behaviour and cognitive functions. The sex with the regional size advantage (male or female) differs between brain areas and species. Among adult songbirds, males have larger brain areas such as the HVC (proper name) and RA (robust nucleus of the arcopallium) that control the production of learned songs. Forest weavers (Ploceus bicolor) mated pairs sing a unison duet in which male and female mates learn to produce identical songs. We show with histological techniques that the volume and neuron numbers of HVC and RA were ≥1.5 times larger in males than in females despite their identical songs. In contrast, using in-situ hybridizations, females have much higher (30–70%) expression levels of mRNA of a number of synapse-related proteins in HVC and/or RA than their male counterparts. Male-typical and female-typical sexual differentiation appears to act on different aspects of the phenotypes within the same brain areas, leading females and males to produce the same behaviour using different cellular mechanisms.
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Affiliation(s)
- Manfred Gahr
- Max Planck Institute for Ornithology, Seewiesen, Germany.
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Tang YP, Peabody C, Tomaszycki ML, Wade J. Sexually dimorphic SCAMP1 expression in the forebrain motor pathway for song production of juvenile zebra finches. Dev Neurobiol 2007; 67:474-82. [PMID: 17443802 PMCID: PMC2878128 DOI: 10.1002/dneu.20354] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Mechanisms regulating sexual differentiation of the zebra finch song system are not well understood. The present study was designed to more fully characterize secretory carrier membrane protein 1 (SCAMP1), which was identified in a cDNA microarray screen as showing increased expression in the forebrains of developing male compared with female zebra finches. We completed the sequence of the open reading frame and used in situ hybridization to compare mRNA in song control regions of juvenile (25-day-old) individuals. Expression was significantly greater in the HVC (used as a proper name) and robust nucleus of the arcopallium (RA) in males than in females. Immunohistochemistry revealed that SCAMP1 protein is also expressed in these two brain regions, and qualitatively appears greater in males. Western analysis confirmed that the protein is increased in the telencephalon of males when compared with females at 25 days of age. These results are consistent with the idea that SCAMP1 is involved in masculinization of these brain areas, perhaps facilitating the survival of cells within them.
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Affiliation(s)
- Yu Ping Tang
- Department of Psychology, Michigan State University, East Lansing, Michigan 48824-1101
- Neuroscience Program, Michigan State University, East Lansing, Michigan 48824-1101
| | - Camilla Peabody
- Department of Psychology, Michigan State University, East Lansing, Michigan 48824-1101
- Neuroscience Program, Michigan State University, East Lansing, Michigan 48824-1101
| | - Michelle L. Tomaszycki
- Department of Psychology, Michigan State University, East Lansing, Michigan 48824-1101
- Neuroscience Program, Michigan State University, East Lansing, Michigan 48824-1101
| | - Juli Wade
- Department of Psychology, Michigan State University, East Lansing, Michigan 48824-1101
- Department of Zoology, Michigan State University, East Lansing, Michigan 48824-1101
- Neuroscience Program, Michigan State University, East Lansing, Michigan 48824-1101
- Correspondence to: J. Wade ()
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Zeng SJ, Song K, Xu N, Zhang XW, Zuo MX. Sex difference in cellular proliferation within the telencephalic ventricle zone of Bengalese finch. Neurosci Res 2007; 58:207-14. [PMID: 17493701 DOI: 10.1016/j.neures.2007.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2006] [Revised: 01/12/2007] [Accepted: 02/01/2007] [Indexed: 11/21/2022]
Abstract
Cellular proliferation within the ventricular zone (VZ) may contribute to sex differences through the net addition of neurons in song control nuclei. To address this issue, we administered [(3)H]thymidine to Bengalese finches of both sexes, and estradiol benzoate (EB) to females 15 days post hatching. The birds were killed 2h later to examine thymidine labeled cells within the VZ at three brain levels, HVC, anterior commissure and Area X. Our results indicated that: (1) cell proliferation in the VZ was significantly higher in the three studied brain levels in males and EB implant females relative to intact or empty implant females, respectively; (2) proliferation in the dorsal half of the VZ, in proximity to HVC, was notably higher than that in the ventral half of the VZ; (3) proliferation in the ventral VZ (VVZ), which is relatively close to Area X was higher relative to other subregions of VZ (dorsal and intermediate). Our study suggests that sex differences in cell proliferation in the VZ may contribute to the net growth of HVC and Area X in males, and estradiol may play an important role in sexual difference in cellular proliferation within the VZ.
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Affiliation(s)
- Shao Ju Zeng
- Key Laboratory for Cell Proliferation And Regulation Biology, Ministry of Education, Beijing Normal University, Beijing 100875, China.
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