title: The importance of having two X chromosomes.
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.
authors.affiliation: 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 arnold@ucla.edu.
authors.forename: Arthur P
authors.initials: AP
authors.lastname: Arnold
authors.affiliation: 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.
authors.forename: Karen
authors.initials: K
authors.lastname: Reue
authors.affiliation: Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
authors.forename: Mansoureh
authors.initials: M
authors.lastname: Eghbali
authors.affiliation: 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.
authors.forename: Eric
authors.initials: E
authors.lastname: Vilain
authors.affiliation: 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.
authors.forename: Xuqi
authors.initials: X
authors.lastname: Chen
authors.affiliation: 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.
authors.forename: Negar
authors.initials: N
authors.lastname: Ghahramani
authors.affiliation: 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.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Itoh
authors.affiliation: Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
authors.forename: Jingyuan
authors.initials: J
authors.lastname: Li
authors.affiliation: 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.
authors.forename: Jenny C
authors.initials: JC
authors.lastname: Link
authors.affiliation: 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.
authors.forename: Tuck
authors.initials: T
authors.lastname: Ngun
authors.affiliation: 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.
authors.forename: Shayna M
authors.initials: SM
authors.lastname: Williams-Burris
mesh_terms: D000818:Animals; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D005838:Genotype; D012739:Gonadal Steroid Hormones / Q000378:metabolism; D008297:Male; D012737:Sex Factors; D014960:X Chromosome / Q000235:genetics*
chemical_list: D012739:Gonadal Steroid Hormones
keywords: Klinefelter; X chromosome; ischaemia; obesity; sex differences; sexual differentiation
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