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Cortes LR, Forger NG. DNA methylation and demethylation shape sexual differentiation of neurochemical phenotype. Horm Behav 2023; 151:105349. [PMID: 37001316 PMCID: PMC10133097 DOI: 10.1016/j.yhbeh.2023.105349] [Citation(s) in RCA: 2] [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: 11/04/2022] [Revised: 02/24/2023] [Accepted: 03/13/2023] [Indexed: 04/28/2023]
Abstract
Some of the best-studied neural sex differences depend on differential cell death in males and females, but other sex differences persist even if cell death is prevented. These include sex differences in neurochemical phenotype (i.e., stable patterns of gene expression). Work in our laboratory over the last several years has tested the hypothesis that sex differences in DNA methylation early in life underlie sexual differentiation of neuronal phenotype. We have shown that 1) expression of enzymes that place or remove DNA methylation marks is greatest during the first week of life in the mouse brain and overlaps with the perinatal critical period of sexual differentiation; 2) a transient inhibition of DNA methylation during neonatal life abolishes several sex differences in cell phenotype in the mouse hypothalamus; 3) both DNA methylation and de-methylation contribute to the development of neural sex differences; and 4) the effects of DNA methylation and de-methylation are brain region- and cell type-specific.
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Affiliation(s)
- L R Cortes
- Department of Integrative Biology & Physiology, University of California Los Angeles, Los Angeles, CA, USA
| | - N G Forger
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA.
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Tsukahara S, Morishita M. Sexually Dimorphic Formation of the Preoptic Area and the Bed Nucleus of the Stria Terminalis by Neuroestrogens. Front Neurosci 2020; 14:797. [PMID: 32848568 PMCID: PMC7403479 DOI: 10.3389/fnins.2020.00797] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 07/07/2020] [Indexed: 01/08/2023] Open
Abstract
Testicular androgens during the perinatal period play an important role in the sexual differentiation of the brain of rodents. Testicular androgens transported into the brain act via androgen receptors or are the substrate of aromatase, which synthesizes neuroestrogens that act via estrogen receptors. The latter that occurs in the perinatal period significantly contributes to the sexual differentiation of the brain. The preoptic area (POA) and the bed nucleus of the stria terminalis (BNST) are sexually dimorphic brain regions that are involved in the regulation of sex-specific social behaviors and the reproductive neuroendocrine system. Here, we discuss how neuroestrogens of testicular origin act in the perinatal period to organize the sexually dimorphic structures of the POA and BNST. Accumulating data from rodent studies suggest that neuroestrogens induce the sex differences in glial and immune cells, which play an important role in the sexually dimorphic formation of the dendritic synapse patterning in the POA, and induce the sex differences in the cell number of specific neuronal cell groups in the POA and BNST, which may be established by controlling the number of cells dying by apoptosis or the phenotypic organization of living cells. Testicular androgens in the peripubertal period also contribute to the sexual differentiation of the POA and BNST, and thus their aromatization to estrogens may be unnecessary. Additionally, we discuss the notion that testicular androgens that do not aromatize to estrogens can also induce significant effects on the sexually dimorphic formation of the POA and BNST.
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Affiliation(s)
- Shinji Tsukahara
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Masahiro Morishita
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
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VanRyzin JW, Marquardt AE, Pickett LA, McCarthy MM. Microglia and sexual differentiation of the developing brain: A focus on extrinsic factors. Glia 2019; 68:1100-1113. [PMID: 31691400 DOI: 10.1002/glia.23740] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 10/09/2019] [Accepted: 10/11/2019] [Indexed: 12/16/2022]
Abstract
Microglia, the innate immune cells of the brain, have recently been removed from the position of mere sentinels and promoted to the role of active sculptors of developing circuits and cells. Alongside their functions in normal brain development, microglia coordinate sexual differentiation of the brain, a set of processes which vary by region and endpoint like that of microglia function itself. In this review, we highlight the ways microglia are both targets and drivers of brain sexual differentiation. We examine the factors that may drive sex differences in microglia, with a special focus on how changing microenvironments in the developing brain dictate microglia phenotypes and discuss how their diverse functions sculpt lasting sex-specific changes in the brain. Finally, we consider how sex-specific early life environments contribute to epigenetic programming and lasting sex differences in microglia identity.
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Affiliation(s)
- Jonathan W VanRyzin
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Ashley E Marquardt
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland
| | - Lindsay A Pickett
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland
| | - Margaret M McCarthy
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland.,Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland
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Morishita M, Maejima S, Tsukahara S. Gonadal Hormone-Dependent Sexual Differentiation of a Female-Biased Sexually Dimorphic Cell Group in the Principal Nucleus of the Bed Nucleus of the Stria Terminalis in Mice. Endocrinology 2017; 158:3512-3525. [PMID: 28977609 DOI: 10.1210/en.2017-00240] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 07/27/2017] [Indexed: 11/19/2022]
Abstract
We recently reported a female-biased sexually dimorphic area in the mouse brain in the boundary region between the preoptic area and the bed nucleus of the stria terminalis (BNST). We reexamined this area and found that it is a ventral part of the principal nucleus of the BNST (BNSTp). The BNSTp is a male-biased sexually dimorphic nucleus, but the ventral part of the BNSTp (BNSTpv) exhibits female-biased sex differences in volume and neuron number. The volume and neuron number of the BNSTpv were increased in males by neonatal orchiectomy and decreased in females by treatment with testosterone, dihydrotestosterone, or estradiol within 5 days after birth. Sex differences in the volume and neuron number of the BNSTpv emerged before puberty. These sex differences became prominent in adulthood with increasing volume in females and loss of neurons in males during the pubertal/adolescent period. Prepubertal orchiectomy did not affect the BNSTpv, although prepubertal ovariectomy reduced the volume increase and induced loss of neurons in the female BNSTpv. In contrast, the volume and neuron number of male-biased sexually dimorphic nuclei that are composed of mainly calbindin neurons and are located in the preoptic area and BNST were decreased by prepubertal orchiectomy but not affected by prepubertal ovariectomy. Testicular testosterone during the postnatal period may defeminize the BNSTpv via binding directly to the androgen receptor and indirectly to the estrogen receptor after aromatization, although defeminization may proceed independently of testicular hormones in the pubertal/adolescent period. Ovarian hormones may act to feminize the BNSTpv during the pubertal/adolescent period.
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Affiliation(s)
- Masahiro Morishita
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan
| | - Sho Maejima
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan
| | - Shinji Tsukahara
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama 338-8570, Japan
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Madden AMK, Paul AT, Pritchard RA, Michel R, Zup SL. Serotonin promotes feminization of the sexually dimorphic nucleus of the preoptic area, but not the calbindin cell group. Dev Neurobiol 2016; 76:1241-1253. [DOI: 10.1002/dneu.22386] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Revised: 12/30/2015] [Accepted: 02/16/2016] [Indexed: 01/20/2023]
Affiliation(s)
- Amanda M. K. Madden
- Graduate Program in Developmental and Brain Sciences; University of Massachusetts Boston; Boston Massachusetts 02125
- Psychology Department; University of Massachusetts Boston; Boston Massachusetts 02125
| | - Alexandria T. Paul
- Psychology Department; University of Massachusetts Boston; Boston Massachusetts 02125
| | - Rory A. Pritchard
- Psychology Department; University of Massachusetts Boston; Boston Massachusetts 02125
| | - Rebecca Michel
- Psychology Department; University of Massachusetts Boston; Boston Massachusetts 02125
| | - Susan L. Zup
- Graduate Program in Developmental and Brain Sciences; University of Massachusetts Boston; Boston Massachusetts 02125
- Psychology Department; University of Massachusetts Boston; Boston Massachusetts 02125
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Forger NG, Strahan JA, Castillo-Ruiz A. Cellular and molecular mechanisms of sexual differentiation in the mammalian nervous system. Front Neuroendocrinol 2016; 40:67-86. [PMID: 26790970 PMCID: PMC4897775 DOI: 10.1016/j.yfrne.2016.01.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 12/31/2015] [Accepted: 01/09/2016] [Indexed: 01/16/2023]
Abstract
Neuroscientists are likely to discover new sex differences in the coming years, spurred by the National Institutes of Health initiative to include both sexes in preclinical studies. This review summarizes the current state of knowledge of the cellular and molecular mechanisms underlying sex differences in the mammalian nervous system, based primarily on work in rodents. Cellular mechanisms examined include neurogenesis, migration, the differentiation of neurochemical and morphological cell phenotype, and cell death. At the molecular level we discuss evolving roles for epigenetics, sex chromosome complement, the immune system, and newly identified cell signaling pathways. We review recent findings on the role of the environment, as well as genome-wide studies with some surprising results, causing us to re-think often-used models of sexual differentiation. We end by pointing to future directions, including an increased awareness of the important contributions of tissues outside of the nervous system to sexual differentiation of the brain.
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Affiliation(s)
- Nancy G Forger
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, United States.
| | - J Alex Strahan
- Neuroscience Institute, Georgia State University, Atlanta, GA 30303, United States.
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McCarthy MM, Pickett LA, VanRyzin JW, Kight KE. Surprising origins of sex differences in the brain. Horm Behav 2015; 76:3-10. [PMID: 25917865 PMCID: PMC4620061 DOI: 10.1016/j.yhbeh.2015.04.013] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 03/22/2015] [Accepted: 04/06/2015] [Indexed: 11/22/2022]
Abstract
This article is part of a Special Issue "SBN 2014". Discerning the biologic origins of neuroanatomical sex differences has been of interest since they were first reported in the late 60's and early 70's. The centrality of gonadal hormone exposure during a developmental critical window cannot be denied but hormones are indirect agents of change, acting to induce gene transcription or modulate membrane bound signaling cascades. Sex differences in the brain include regional volume differences due to differential cell death, neuronal and glial genesis, dendritic branching and synaptic patterning. Early emphasis on mechanism therefore focused on neurotransmitters and neural growth factors, but by and large these endpoints failed to explain the origins of neural sex differences. More recently evidence has accumulated in favor of inflammatory mediators and immune cells as principle regulators of brain sexual differentiation and reveal that the establishment of dimorphic circuits is not cell autonomous but instead requires extensive cell-to-cell communication including cells of non-neuronal origin. Despite the multiplicity of cells involved the nature of the sex differences in the neuroanatomical endpoints suggests canalization, a process that explains the robustness of individuals in the face of intrinsic and extrinsic variability. We propose that some neuroanatomical endpoints are canalized to enhance sex differences in the brain by reducing variability within one sex while also preventing the sexes from diverging too greatly. We further propose mechanisms by which such canalization could occur and discuss what relevance this may have to sex differences in behavior.
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Affiliation(s)
- Margaret M McCarthy
- Department of Pharmacology, Program in Neuroscience and Program in Molecular Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| | - Lindsay A Pickett
- Department of Pharmacology, Program in Neuroscience and Program in Molecular Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Jonathan W VanRyzin
- Department of Pharmacology, Program in Neuroscience and Program in Molecular Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Katherine E Kight
- Department of Pharmacology, Program in Neuroscience and Program in Molecular Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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He Z, Ferguson SA, Cui L, Greenfield LJ, Paule MG. Development of the sexually dimorphic nucleus of the preoptic area and the influence of estrogen-like compounds. Neural Regen Res 2014; 8:2763-74. [PMID: 25206587 PMCID: PMC4145994 DOI: 10.3969/j.issn.1673-5374.2013.29.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 08/29/2013] [Indexed: 11/18/2022] Open
Abstract
One of the well-defined sexually dimorphic structures in the brain is the sexually dimorphic nucleus, a cluster of cells located in the preoptic area of the hypothalamus. The rodent sexually dimorphic nucleus of the preoptic area can be delineated histologically using conventional Nissl staining or immunohistochemically using calbindin D28K immunoreactivity. There is increasing use of the bindin D28K-delineated neural cluster to define the sexually dimorphic nucleus of the preoptic area in rodents. Several mechanisms are proposed to underlie the processes that contribute to the sexual dimorphism (size difference) of the sexually dimorphic nucleus of the preoptic area. Recent evidence indicates that stem cell activity, including proliferation and migration presumably from the 3rd ventricle stem cell niche, may play a critical role in the postnatal development of the sexually dimorphic nucleus of the preoptic area and its distinguishing sexually dimorphic feature: a signifi-cantly larger volume in males. Sex hormones and estrogen-like compounds can affect the size of the sexually dimorphic nucleus of the preoptic area. Despite considerable research, it remains un-clear whether estrogen-like compounds and/or sex hormones increase size of the sexually dimor-phic nucleus of the preoptic area via an increase in stem cell activity originating from the 3rd ventricle stem cell niche.
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Affiliation(s)
- Zhen He
- Division of Neurotoxicology, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR 72079, USA ; Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, AR 72005, USA
| | - Sherry Ann Ferguson
- Division of Neurotoxicology, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR 72079, USA
| | - Li Cui
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, AR 72005, USA
| | - Lazar John Greenfield
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, AR 72005, USA
| | - Merle Gale Paule
- Division of Neurotoxicology, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR 72079, USA
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He Z, Ferguson SA, Cui L, Greenfield LJ, Paule MG. Role of neural stem cell activity in postweaning development of the sexually dimorphic nucleus of the preoptic area in rats. PLoS One 2013; 8:e54927. [PMID: 23383001 PMCID: PMC3559780 DOI: 10.1371/journal.pone.0054927] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Accepted: 12/19/2012] [Indexed: 02/07/2023] Open
Abstract
The sexually dimorphic nucleus of the preoptic area (SDN-POA) has received increased attention due to its apparent sensitivity to estrogen-like compounds found in food and food containers. The mechanisms that regulate SDN-POA volume remain unclear as is the extent of postweaning development of the SDN-POA. Here we demonstrate that the female Sprague-Dawley SDN-POA volume increased from weaning to adulthood, although this increase was not statistically significant as it was in males. The number of cells positive for Ki67, a marker of cell proliferation, in both the SDN-POA and the hypothalamus was significantly higher at weaning than at adulthood in male rats. In contrast, the number of Ki67-positive cells was significantly higher in the hypothalamus but not in the SDN-POA (p>0.05) at weaning than at adulthood in female rats. A subset of the Ki67-positive cells in the SDN-POA displayed the morphology of dividing cells. Nestin-immunoreactivity delineated a potential macroscopic neural stem cell niche in the rostral end of the 3rd ventricle. In conclusion, stem cells may partially account for the sexually dimorphic postweaning development of the SDN-POA.
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Affiliation(s)
- Zhen He
- Division of Neurotoxicology, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR, USA.
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