51
|
Burgoyne PS, Arnold AP. A primer on the use of mouse models for identifying direct sex chromosome effects that cause sex differences in non-gonadal tissues. Biol Sex Differ 2016; 7:68. [PMID: 27999654 PMCID: PMC5154145 DOI: 10.1186/s13293-016-0115-5] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Accepted: 11/08/2016] [Indexed: 12/15/2022] Open
Abstract
In animals with heteromorphic sex chromosomes, all sex differences originate from the sex chromosomes, which are the only factors that are consistently different in male and female zygotes. In mammals, the imbalance in Y gene expression, specifically the presence vs. absence of Sry, initiates the differentiation of testes in males, setting up lifelong sex differences in the level of gonadal hormones, which in turn cause many sex differences in the phenotype of non-gonadal tissues. The inherent imbalance in the expression of X and Y genes, or in the epigenetic impact of X and Y chromosomes, also has the potential to contribute directly to the sexual differentiation of non-gonadal cells. Here, we review the research strategies to identify the X and Y genes or chromosomal regions that cause direct, sexually differentiating effects on non-gonadal cells. Some mouse models are useful for separating the effects of sex chromosomes from those of gonadal hormones. Once direct “sex chromosome effects” are detected in these models, further studies are required to narrow down the list of candidate X and/or Y genes and then to identify the sexually differentiating genes themselves. Logical approaches to the search for these genes are reviewed here.
Collapse
Affiliation(s)
- Paul S Burgoyne
- Stem Cell Biology and Developmental Genetics, Mill Hill Laboratory, Francis Crick Institute, The Ridgeway, London, NW7 1AA UK
| | - Arthur P Arnold
- Department of Integrative Biology and Physiology, and Laboratory of Neuroendocrinology of the Brain Research Institute, University of California, Los Angeles, 610 Charles Young Drive South, Los Angeles, CA 90095-7239 USA
| |
Collapse
|
52
|
Lin CY, Huang SC, Tung CC, Chou CH, Gau SSF, Huang HS. Analysis of Genome-Wide Monoallelic Expression Patterns in Three Major Cell Types of Mouse Visual Cortex Using Laser Capture Microdissection. PLoS One 2016; 11:e0163663. [PMID: 27662371 PMCID: PMC5035046 DOI: 10.1371/journal.pone.0163663] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 09/12/2016] [Indexed: 12/11/2022] Open
Abstract
Genomic imprinting is an epigenetic mechanism causing monoallelic expression in a parent-of-origin-specific manner. Disruption of imprinted genes causes various neurological and psychiatric disorders. However, the role of imprinted genes in the brain is largely unknown. Different cell types within distinct brain regions can influence the genomic imprinting status, but imprinted genes in single cell types within distinct brain regions have not been characterized on a genome-wide scale. To address this critical question, we used a multi-stage approach, which combined genetically engineered mice with fluorescence-based laser capture microdissection (LCM) to capture excitatory neurons, inhibitory neurons and astrocytes as single cells in layer 2/3 of mouse visual cortex. RNA sequencing determined parental expression patterns on a genome-wide scale in the captured cells within specific brain regions. The expression level of cell-type-specific genes for excitatory neurons (13 genes), inhibitory neurons (16 genes) and astrocytes (20 genes) confirmed the LCM-captured cells maintained their cellular identities. The parent-of-origin-specific expression pattern of imprinted genes, including maternally expressed Meg3 and paternally expressed Peg3, provided evidence that the status of known imprinted genes was also maintained. Although our platform remains to be improved, our findings demonstrate the parental expression pattern can be analysed not only at the level of a single cell type but also at the level of specific cortical layers. Our approach has the potential to reveal novel regulatory modules associated with plasticity through genomic imprinting mechanisms in different cell types, not only in the visual cortex but also in other brain regions.
Collapse
Affiliation(s)
- Chia-Yi Lin
- Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Shih-Chuan Huang
- Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chun-Che Tung
- Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chih-Hsuan Chou
- Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Susan Shur-Fen Gau
- Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan
- Department of Psychiatry, College of Medicine, National Taiwan University, Taipei, Taiwan
- Clinical Center for Neuroscience and Behavior, National Taiwan University Hospital, Taipei, Taiwan
- Neurobiology and Cognitive Science Center, National Taiwan University, Taipei, Taiwan
| | - Hsien-Sung Huang
- Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan
- Clinical Center for Neuroscience and Behavior, National Taiwan University Hospital, Taipei, Taiwan
- Neurobiology and Cognitive Science Center, National Taiwan University, Taipei, Taiwan
- Ph.D. Program in Translational Medicine, National Taiwan University and Academia Sinica, Taipei, Taiwan
- Neurodevelopment Club in Taiwan, Taipei, Taiwan
- * E-mail:
| |
Collapse
|
53
|
Perez JD, Rubinstein ND, Dulac C. New Perspectives on Genomic Imprinting, an Essential and Multifaceted Mode of Epigenetic Control in the Developing and Adult Brain. Annu Rev Neurosci 2016; 39:347-84. [PMID: 27145912 DOI: 10.1146/annurev-neuro-061010-113708] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Mammalian evolution entailed multiple innovations in gene regulation, including the emergence of genomic imprinting, an epigenetic regulation leading to the preferential expression of a gene from its maternal or paternal allele. Genomic imprinting is highly prevalent in the brain, yet, until recently, its central roles in neural processes have not been fully appreciated. Here, we provide a comprehensive survey of adult and developmental brain functions influenced by imprinted genes, from neural development and wiring to synaptic function and plasticity, energy balance, social behaviors, emotions, and cognition. We further review the widespread identification of parental biases alongside monoallelic expression in brain tissues, discuss their potential roles in dosage regulation of key neural pathways, and suggest possible mechanisms underlying the dynamic regulation of imprinting in the brain. This review should help provide a better understanding of the significance of genomic imprinting in the normal and pathological brain of mammals including humans.
Collapse
Affiliation(s)
- Julio D Perez
- Department of Molecular and Cellular Biology, Harvard University, Howard Hughes Medical Institute, Cambridge, Massachusetts 02138;
| | - Nimrod D Rubinstein
- Department of Molecular and Cellular Biology, Harvard University, Howard Hughes Medical Institute, Cambridge, Massachusetts 02138;
| | - Catherine Dulac
- Department of Molecular and Cellular Biology, Harvard University, Howard Hughes Medical Institute, Cambridge, Massachusetts 02138;
| |
Collapse
|
54
|
Arnold AP, Reue K, Eghbali M, Vilain E, Chen X, Ghahramani N, Itoh Y, Li J, Link JC, Ngun T, Williams-Burris SM. The importance of having two X chromosomes. Philos Trans R Soc Lond B Biol Sci 2016; 371:20150113. [PMID: 26833834 DOI: 10.1098/rstb.2015.0113] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/08/2015] [Indexed: 12/14/2022] Open
Abstract
Historically, it was thought that the number of X chromosomes plays little role in causing sex differences in traits. Recently, selected mouse models have been used increasingly to compare mice with the same type of gonad but with one versus two copies of the X chromosome. Study of these models demonstrates that mice with one X chromosome can be strikingly different from those with two X chromosomes, when the differences are not attributable to confounding group differences in gonadal hormones. The number of X chromosomes affects adiposity and metabolic disease, cardiovascular ischaemia/reperfusion injury and behaviour. The effects of X chromosome number are likely the result of inherent differences in expression of X genes that escape inactivation, and are therefore expressed from both X chromosomes in XX mice, resulting in a higher level of expression when two X chromosomes are present. The effects of X chromosome number contribute to sex differences in disease phenotypes, and may explain some features of X chromosome aneuploidies such as in Turner and Klinefelter syndromes.
Collapse
Affiliation(s)
- Arthur P Arnold
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA, USA Laboratory of Neuroendocrinology, UCLA Brain Research Institute, Los Angeles, CA, USA
| | - Karen Reue
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA, USA Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Mansoureh Eghbali
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Eric Vilain
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA Department of Pediatrics, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA Department of Urology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Xuqi Chen
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA, USA Laboratory of Neuroendocrinology, UCLA Brain Research Institute, Los Angeles, CA, USA
| | - Negar Ghahramani
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA Laboratory of Neuroendocrinology, UCLA Brain Research Institute, Los Angeles, CA, USA
| | - Yuichiro Itoh
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA, USA Laboratory of Neuroendocrinology, UCLA Brain Research Institute, Los Angeles, CA, USA
| | - Jingyuan Li
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Jenny C Link
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA, USA Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Tuck Ngun
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA Laboratory of Neuroendocrinology, UCLA Brain Research Institute, Los Angeles, CA, USA
| | - Shayna M Williams-Burris
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA, USA Interdepartmental Program for Neuroscience, University of California, Los Angeles, Los Angeles, CA, USA Laboratory of Neuroendocrinology, UCLA Brain Research Institute, Los Angeles, CA, USA
| |
Collapse
|