Sexual differentiation in the developing mouse brain: contributions of sex chromosome genes - PubMed (original) (raw)

Sexual differentiation in the developing mouse brain: contributions of sex chromosome genes

J T Wolstenholme et al. Genes Brain Behav. 2013 Mar.

Abstract

Neural sexual differentiation begins during embryogenesis and continues after birth for a variable amount of time depending on the species and brain region. Because gonadal hormones were the first factors identified in neural sexual differentiation, their role in this process has eclipsed investigation of other factors. Here, we use a mouse with a spontaneous translocation that produces four different unique sets of sex chromosomes. Each genotype has one normal X-chromosome and a unique second sex chromosome creating the following genotypes: XY(*x) , XX, XY(*) , XX(Y) (*) . This Y(*) mouse line is used by several laboratories to study two human aneuploid conditions: Turner and Klinefelter syndromes. As sex chromosome number affects behavior and brain morphology, we surveyed brain gene expression at embryonic days 11.5 and 18.5 to isolate X-chromosome dose effects in the developing brain as possible mechanistic changes underlying the phenotypes. We compared gene expression differences between gonadal males and females as well as individuals with one vs. two X-chromosomes. We present data showing, in addition to genes reported to escape X-inactivation, a number of autosomal genes are differentially expressed between the sexes and in mice with different numbers of X-chromosomes. Based on our results, we can now identify the genes present in the region around the chromosomal break point that produces the Y(*) model. Our results also indicate an interaction between gonadal development and sex chromosome number that could further elucidate the role of sex chromosome genes and hormones in the sexual differentiation of behavior.

© 2012 Blackwell Publishing Ltd and International Behavioural and Neural Genetics Society.

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Figures

Figure 1

Figure 1. Numbers of genes significantly altered by age, sex or genotype in the Y* mouse brain

Numbers and associated arrows shown between age, sex or genotype indicate the number of differentially expressed genes called for a given comparison. The majority of gene expression changes occurred between embryonic day (E) 11.5 and 18.5 within each genotype. Far fewer genes were significantly altered between genotype or sex. XX = normal female, XY*X = 1X female, XXY* = 2X male, XY* = normal male.

Figure 2

Figure 2. Genes escaping X-inactivation at E11.5 and E18.5

Quantitative PCR of relative gene expression for X-inactive specific transcript (Xist) at A. E11.5 and B. E18.5, eukaryotic translation initiation factor 2 subunit 3 X-linked (Eif2s3x) at C. E11.5 and D. E18.5, lysine(K)-specific demethylase 6a (Kdm6a) at E. E11.5 and F. E18.5 and lysine(K)-specific demethylase 6a (Kdm5c) at G. E11.5 and H. E18.5. Expression is relative to peptidylprolyl isomerase B (Ppib) and normalized to XX females. * p<0.05 main effect of X-chromosome number.

Figure 3

Figure 3. Genes located on distal tip of X-chromosome with expression higher in 1X mice at E11.5 and E18.5

Quantitative PCR of relative gene expression for BC022960 , an uncharacterized transcript at A. E11.5 and B. E18.5, holocytochrome c synthase (Hccs) at C. E11.5 and D. E18.5, male specific lethal 3 (Msl3) at E. E11.5 and F. E18.5, and midline-1 (Mid1) at G. E11.5 and H. E18.5. Expression is relative to peptidylprolyl isomerase B (Ppib) and normalized to XX females. * p<0.05 main effect of X-chromosome number.

Figure 4

Figure 4. Gene expression levels of the DCC complex in adult cerebellum

Quantitative PCR of relative gene expression for A. male specific lethal 3, (Msl3), B. Relative copy number of genomic DNA for Msl3, C. male specific lethal 1 (Msl1), D. male specific lethal 2 (Msl2). E. dead box polypeptide 9 (Dhx9), F. Myst histone acetyltransferase 1 (Myst1). Expression is relative to peptidylprolyl isomerase B (Ppib) and normalized to XX females. * p<0.05 main effect of X-chromosome number.

Figure 5

Figure 5. Schematic of the mouse X-chromosome with an overlay of genes reported to escape X-inactivation

Transcripts significantly altered in 1X vs. 2X mice at embryonic day 11.5 and 18.5 as described. Up arrows indicate gene expression levels are higher in 2X mice versus 1X mice and escape X-inactivation. Down arrows indicate decreased gene expression in 2X vs. 1X mice. On the right of the schematic, we show the name and location of genes previously reported to escape X-inactivation (Reinius et al. 2010; Yang et al. 2010).

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