46,XX individuals with classical congenital adrenal hyperplasia (CAH) due to deficiency of the enzyme, 21-hydroxylase, show variable degrees of masculinization of body and behavior due to excess adrenal androgen production. Increased bisexuality and homosexuality have also been reported. This article provides a review of existing reports of the latter and presents a new study aimed at replicating the previous findings with detailed assessments of sexual orientation on relatively large samples, and at extending the investigation to the mildest form, non-classical (NC) CAH. Also, this is the first study to relate sexual orientation to the specific molecular genotypes of CAH. In the present study, 40 salt-wasters (SW), 21 SV (simple-virilizing), 82 NC, and 24 non-CAH control women (sisters and female cousins of CAH women) were blindly administered the Sexual Behavior Assessment Schedule (SEBAS-A, 1983 ed.; H. F. L. Meyer-Bahlburg & A. A. Ehrhardt, Privately printed). Most women were heterosexual, but the rates of bisexual and homosexual orientation were increased above controls not only in women with classical CAH, but also in NC women, and correlated with the degree of prenatal androgenization. Classifying women by molecular genotypes did not further increase the correlation. Diverse aspects of sexual orientation were highly intercorrelated, and principal components analysis yielded one general factor. Bisexual/homosexual orientation was (modestly) correlated with global measures of masculinization of non-sexual behavior and predicted independently by the degree of both prenatal androgenization and masculinization of childhood behavior. We conclude that the findings support a sexual-differentiation perspective involving prenatal androgens on the development of sexual orientation.

Monozygotic (MZ) twins may be subject to epigenetic modifications that could result in different patterns of gene expression. Several lines of evidence suggest that epigenetic factors may underlie mental disorders such as bipolar disorder (BD) and schizophrenia (SZ). One important epigenetic modification, of relevance to female MZ twins, is X-chromosome inactivation. Some MZ female twin pairs are discordant for monogenic X linked disorders because of differential X inactivation. We postulated that similar mechanisms may also occur in disorders with more complex inheritance including BD and SZ. Examination of X-chromosome inactivation patterns in DNA samples from blood and/or buccal swabs in a series of 63 female MZ twin pairs concordant or discordant for BD or SZ and healthy MZ controls suggests a potential contribution from X-linked loci to discordance within twin pairs for BD but is inconclusive for SZ. Discordant female bipolar twins showed greater differences in the methylation of the maternal and paternal X alleles than concordant twin pairs and suggest that differential skewing of X-chromosome inactivation may contribute to the discordance observed for bipolar disorder in female MZ twin pairs and the potential involvement of X-linked loci in the disorder.(c) 2007 Wiley-Liss, Inc.

Pre-eclampsia is a disorder that affects approximately 5% of pregnancies. We tested the hypothesis that skewed X-chromosome inactivation (XCI) could be involved in the pathogenesis of pre-eclampsia. Peripheral blood DNA was obtained from 67 pre-eclampsia patients and 130 control women. Androgen receptor (AR) was analyzed by the HpaII/polymerase chain reaction assay to assess XCI patterns in DNA extracted from peripheral-blood cells. In addition, buccal cells were obtained from seven patients, and the analysis repeated. Extremely skewed XCI was observed in 10 of 46 informative patients (21.74%), and in 2 of 86 informative controls (2.33%, P = 0.0005; chi(2) test). Our findings support a role for the X-chromosome in the pathogenesis of pre-eclampsia in a subgroup of patients.

Accumulating evidence in rodents suggests that a prolactin locally synthesized and released within the brain can act together with that taken up from the circulation to modulate neuroendocrine responses. The present study was designed to identify the regional patterns of prolactin expression in the adult and developing sheep brain. Specifically, we tested the hypothesis that prolactin is expressed in regions of the adult and fetal sheep brain that are critical in the development of neuroendocrine homeostatic and behavioral functions. The expression of prolactin protein in sheep brain was demonstrated by Western blot analysis and brain prolactin mRNA was detected and sequenced using RT-PCR. In situ hybridization histochemistry revealed that prolactin mRNA was expressed in the medial preoptic area, periventricular preoptic nucleus, bed nucleus of the stria terminalis, and in the paraventricular nucleus of the hypothalamus, particularly the ventral region. The neuroanatomical distribution of prolactin mRNA was best visualized in the fetus and prolactin-immunoreactive neurons could also be identified in late gestation fetuses. Brain prolactin mRNA was expressed as early as day 60 of gestation and increased as the fetus aged and peaked at day 135 (term = 147 days). Prolactin mRNA expression did not exhibit a sex difference in the preoptic area, but in the amygdala prolactin mRNA was significantly higher in females than in males at day 100 of gestation. We conclude that prolactin expressed in adult and fetal sheep brain could be involved in neurodevelopment and/or modulation of the neuroendocrine stress axis, although it is too early to rule out other possibilities given the diverse actions that have been attributed to prolactin. Copyright (c) 2008 S. Karger AG, Basel.

Sex determination is the commitment of an organism toward male or female development. Traditionally, in mammals, sex determination is considered equivalent to gonadal determination. Since the presence or the absence of the testes ultimately determines the phenotype of the external genitalia, sex determination is typically seen as equivalent to testis determination. But what exactly does sex determine? The endpoint of sex determination is almost invariably seen as the reproductive structures, which represent the most obvious phenotypic difference between the sexes. One could argue that the most striking differences between males and females are not the anatomy of the genitals, but the size of the gametes-considerably larger in females than males. In fact, there could be many different endpoints to sex determination, leading to differences between the sexes: brain sexual differences, behavioral differences, and susceptibility to disease. The central dogma of sexual differentiation, stemming initially from the gonad-transfer experiments of Alfred Jost, is that sexual dimorphisms of all somatic tissues are dependent on the testicular secretion of the developing fetus. In this chapter, we will take the example of sex differences in brain and behavior as an endpoint of sex determination. We will argue that genetic factors play a role in sexually dimorphic traits such as the number of dopaminergic cells in the mesencephalon, aggression, and sexual orientation, independently from gonadal hormones.

The classic view of brain sexual differentiation and behavior is that gonadal steroid hormones act directly to promote sex differences in neural and behavioral development. In particular, the actions of testosterone and its metabolites induce a masculine pattern of brain development, while inhibiting feminine neural and behavioral patterns of differentiation. However, recent evidence indicates that gonadal hormones may not solely be responsible for sex differences in brain development and behavior between males and females. Here we examine an alternative hypothesis that genes, by directly inducing sexually dimorphic patterns of neural development, can influence the sexual differences between male and female brains. Using microarrays and RT-PCR, we have detected over 50 candidate genes for differential sex expression, and confirmed at least seven murine genes which show differential expression between the developing brains of male and female mice at stage 10.5 days post coitum (dpc), before any gonadal hormone influence. The identification of genes differentially expressed between male and female brains prior to gonadal formation suggests that genetic factors may have roles in influencing brain sexual differentiation.

ABSTRACT: BACKGROUND: We performed gene expression profiling of the amygdala and hippocampus taken from inbred mouse strains C57BL/6J and A/J. The selected brain areas are implicated in neurobehavioral traits while these mouse strains are known to differ widely in behavior. Consequently, we hypothesized that comparing gene expression profiles for specific brain regions in these strains might provide insight into the molecular mechanisms of human neuropsychiatric traits. We performed a whole-genome gene expression experiment and applied a systems biology approach using weighted gene co-expression network analysis. RESULTS: We were able to identify modules of co-expressed genes that distinguish a strain or brain region. Analysis of the networks that are most informative for hippocampus and amygdala revealed enrichment in neurologically, genetically and psychologically related pathways. Close examination of the strain-specific gene expression profiles, however, revealed no functional relevance but a significant enrichment of single nucleotide polymorphisms in the probe sequences used for array hybridization. This artifact was not observed for the modules of co-expressed genes that distinguish amygdala and hippocampus. CONCLUSIONS: The brain-region specific modules were found to be independent of genetic background and are therefore likely to represent biologically relevant molecular networks that can be studied to complement our knowledge about pathways in neuropsychiatric disease.

The fear of experiencing discrimination often provokes symptoms of psychological distress. One coping resource is positive identification with one's social group-known as collective self-esteem. This preliminary study investigated whether collective self-esteem was related to fears regarding a transsexual identity and psychological distress among 53 self-identified male-to-female transsexuals (mean age = 50.79). Participants were recruited from transgender events held in Arizona and California. The majority (81%) reported living full-time as women (mean length of time living as a woman = 6.33 years). Negative feelings about the transsexual community and fears regarding the impact of a transsexual identity were positively related to psychological distress. A regression model revealed that the fear of how a transsexual identity would affect one's life was the best predictor of the severity of psychological distress. These results are consistent with findings from other historically marginalized groups whereby the stress of being stigmatized by society adversely affects mental health.

Glioblastoma, the most common malignant brain tumor, is among the most lethal and difficult cancers to treat. Although epidermal growth factor receptor (EGFR) mutations are frequent in glioblastoma, their clinical relevance is poorly understood. Studies of tumors from patients treated with the EGFR inhibitor lapatinib revealed that EGFR induces the cleavage and nuclear translocation of the master transcriptional regulator of fatty acid synthesis, sterol regulatory element-binding protein 1 (SREBP-1). This response was mediated by Akt; however, clinical data from rapamycin-treated patients showed that SREBP-1 activation was independent of the mammalian target of rapamycin complex 1, possibly explaining rapamycin's poor efficacy in the treatment of such tumors. Glioblastomas without constitutively active EGFR signaling were resistant to inhibition of fatty acid synthesis, whereas introduction of a constitutively active mutant form of EGFR, EGFRvIII, sensitized tumor xenografts in mice to cell death, which was augmented by the hydroxymethylglutaryl coenzyme A reductase inhibitor atorvastatin. These results identify a previously undescribed EGFR-mediated prosurvival metabolic pathway and suggest new therapeutic approaches to treating EGFR-activated glioblastomas.

We hypothesized that a common SNP in the 3' untranslated region of the upstream transcription factor 1 (USF1), rs3737787, may affect lipid traits by influencing gene expression levels, and we investigated this possibility utilizing the Mexican population, which has a high predisposition to dyslipidemia. We first associated rs3737787 genotypes in Mexican Familial Combined Hyperlipidemia (FCHL) case/control fat biopsies, with global expression patterns. To identify sets of co-expressed genes co-regulated by similar factors such as transcription factors, genetic variants, or environmental effects, we utilized weighted gene co-expression network analysis (WGCNA). Through WGCNA in the Mexican FCHL fat biopsies we identified two significant Triglyceride (TG)-associated co-expression modules. One of these modules was also associated with FCHL, the other FCHL component traits, and rs3737787 genotypes. This USF1-regulated FCHL-associated (URFA) module was enriched for genes involved in lipid metabolic processes. Using systems genetics procedures we identified 18 causal candidate genes in the URFA module. The FCHL causal candidate gene fatty acid desaturase 3 (FADS3) was associated with TGs in a recent Caucasian genome-wide significant association study and we replicated this association in Mexican FCHL families. Based on a USF1-regulated FCHL-associated co-expression module and SNP rs3737787, we identify a set of causal candidate genes for FCHL-related traits. We then provide evidence from two independent datasets supporting FADS3 as a causal gene for FCHL and elevated TGs in Mexicans.

The protein 14-3-3sigma is involved in the regulation of cellular processes such as apoptosis, cell cycle progression and proliferation. Disruption of protein expression has been implicated in a number of malignancies. Here we examine the expression pattern of 14-3-3sigma in breast cancer and specifically consider whether expression in ductal carcinoma in situ (DCIS) lesions is predictive of disease outcome. We examined 14-3-3sigma protein expression and localization using immunohistochemical staining on a high-density tissue microarray consisting of 157 invasive breast cancer patients. Statistical analyses were used to assess the correlation of 14-3-3sigma expression with clinico-pathological parameters and patient outcome. We observed a statistically significant increase in 14-3-3sigma protein expression in ductal hyperplasia, DCIS, and invasive ductal carcinoma (IDC) as compared normal glandular epithelium. In IDC, lower expression of 14-3-3sigma tended to predicted poorer survival time while in DCIS lesions, there was a stronger correlation between relatively higher levels of 14-3-3sigma predicting shorter survival time. Further, of patients who had concurrent DCIS and IDC lesions, those that exhibited a decrease of 14-3-3sigma expression from DCIS to IDC had significantly shorter survival time. Our findings indicate that 14-3-3sigma expression may be a useful prognostic indicator for survival in patients with breast cancer with an elevated 14-3-3sigma in earlier disease predicting a less favorable disease outcome. To our knowledge this is the first published study associating 14-3-3sigma protein expression with breast cancer survival.

ABSTRACT: BACKGROUND: Amyotrophic Lateral Sclerosis (ALS) is a lethal disorder characterized by progressive degeneration of motor neurons in the brain and spinal cord. Diagnosis is mainly based on clinical symptoms, and there is currently no therapy to stop the disease or slow its progression. Since access to spinal cord tissue is not possible at disease onset, we investigated changes in gene expression profiles in whole blood of ALS patients. RESULTS: Our transcriptional study showed dramatic changes in blood of ALS patients; 2,300 probes (9.4%) showed significant differential expression in a discovery dataset consisting of 30 ALS patients and 30 healthy controls. Weighted gene co-expression network analysis (WGCNA) was used to find disease-related networks (modules) and disease related hub genes. Two large co-expression modules were found to be associated with ALS. Our findings were replicated in a second (30 patients and 30 controls) and third dataset (63 patients and 63 controls), thereby demonstrating a highly significant and consistent association of two large co-expression modules with ALS disease status. Ingenuity Pathway Analysis of the ALS related module genes implicates enrichment of functional categories related to genetic disorders, neurodegeneration of the nervous system and inflammatory disease. The ALS related modules contain a number of candidate genes possibly involved in pathogenesis of ALS. CONCLUSIONS: This first large-scale blood gene expression study in ALS observed distinct patterns between cases and controls which may provide opportunities for biomarker development as well as new insights into the molecular mechanisms of the disease.

Human sexual orientation is a complex trait, influenced by several genes, experiential and sociocultural factors. These elements interact and produce a typical pattern of sexual orientation towards the opposite sex. Some exceptions exist, like bisexuality and homosexuality, which seem to be more frequent in males than females. Traditional methods for the genetic study of behavior multifactorial characteristics consist in detecting the presence of familial aggregation. In order to identify the importance of genetic and environmental factors in this aggregation, the concordance of the trait for monozygotic and dizygotic twins and for adopted sibs, reared together and apart, is compared. These types of studies have shown that familial aggregation is stronger for male than for female homosexuality. Based on the threshold method for multifactorial traits, and varying the frequency of homosexuality in the population between 4 and 10%, heritability estimates between 0.27 and 0.76 have been obtained. In 1993, linkage between homosexuality and chromosomal region Xq28 based on molecular approaches was reported. Nevertheless, this was not confirmed in later studies. Recently, a wide search of the genome has given significant or close to significant linkage values with regions 7q36, 8p12 and 10q26, which need to be studied more closely. Deviation in the proportion of X chromosome inactivation in mothers of homosexuals seems to favor the presence of genes related with sexual orientation in this chromosome. There is still much to be known about the genetics of human homosexuality.

X chromosome inactivation is a stochastic event that occurs early in female embryo development to achieve dosage compensation with males. Certain genetic mechanisms affect the normal process causing a skewed X inactivation pattern which has clinical relevance in female carriers of X-linked recessive disorders, like haemophilia. The most commonly used assay to evaluate the X inactivation pattern is the PCR amplification of the human androgen receptor gene (HUMARA). The use of this technique in bleeding carriers and women with haemophilia allows identifying if their hemorrhagic symptoms are due to an unfavourable lyonization. Furthermore, these studies are important for understanding the X chromosome inactivation process in humans.

The X chromosome inactivation pattern in peripheral blood cells becomes more skewed after age 55, and a genetic effect on this age-related skewing has been reported. We investigated the effect of age on X inactivation phenotype in blood, buccal cells and tissue from duodenal biopsies in 80 females aged 19-90 years. The X inactivation pattern correlated positively with age in blood (r = 0.238, P = 0.034) and buccal cells (r = 0.260, P = 0.02). The mean degree of skewing was higher in the elderly (>/=55 years) than in the young (<55 years) in blood (70.1 and 63.5%, respectively, P = 0.013) and in buccal cells (64.7 and 59.0%, respectively, P = 0.004). Correlation of X inactivation between the different tissues was high in all tissues with a tendency to increase with age for blood and buccal cells (P = 0.082). None of the duodenal biopsies had a skewed X inactivation, and the mean degree of skewing was similar in the two age groups. The tendency for the same X chromosome to be the preferentially active X in both blood and buccal cells with advancing age is in agreement with a genetic effect on age-related skewing and indicates that genes other than those involved in hematopoiesis should be investigated in the search for genes contributing to age related skewing.

Rett syndrome is a largely sporadic, X-linked neurological disorder with a characteristic phenotype, but which exhibits substantial phenotypic variability. This variability has been partly attributed to an effect of X chromosome inactivation (XCI). There have been conflicting reports regarding incidence of skewed X inactivation in Rett syndrome. In rare familial cases of Rett syndrome, favourably skewed X inactivation has been found in phenotypically normal carrier mothers. We have investigated the X inactivation pattern in DNA from blood and buccal cells of sporadic Rett patients (n=96) and their mothers (n=84). The mean degree of skewing in blood was higher in patients (70.7%) than controls (64.9%). Unexpectedly, the mothers of these patients also had a higher mean degree of skewing in blood (70.8%) than controls. In accordance with these findings, the frequency of skewed (XCI >/=80%) X inactivation in blood was also higher in both patients (25%) and mothers (30%) than in controls (11%). To test whether the Rett patients with skewed X inactivation were daughters of skewed mothers, 49 mother-daughter pairs were analysed. Of 14 patients with skewed X inactivation, only three had a mother with skewed X inactivation. Among patients, mildly affected cases were shown to be more skewed than more severely affected cases, and there was a trend towards preferential inactivation of the paternally inherited X chromosome in skewed cases. These findings, particularly the greater degree of X inactivation skewing in Rett syndrome patients, are of potential significance in the analysis of genotype-phenotype correlations in Rett syndrome.European Journal of Human Genetics advance online publication, 5 July 2006; doi:10.1038/sj.ejhg.5201682.

The mammalian X-chromosome exists in two flavors, active and inactive, in each cell of the adult female. This phenomenon originates from the process of random choice occuring early in development in a small number of progenitor cells in which the decision is made to inactivate either one or the other X chromosome on a cell-autonomous basis. Once made, this initial decision is irreversible, although exceptions exist in specific chromosomal territories and cell lineages. Recent findings implicate various factors, including non-coding RNAs and chromatin modification complexes, as effectors in the initiation and maintenance of X-chromosome inactivation. The functional redundancy of such factors almost certainly plays an important role in the stability of the inactive X. Studying skewing or bias opens an important opportunity for understanding facets of the random choice process.

Human sexual preference is a sexually dimorphic trait with a substantial genetic component. Linkage of male sexual orientation to markers on the X chromosome has been reported in some families. Here, we measured X chromosome inactivation ratios in 97 mothers of homosexual men and 103 age-matched control women without gay sons. The number of women with extreme skewing of X-inactivation was significantly higher in mothers of gay men (13/97=13%) compared to controls (4/103=4%) and increased in mothers with two or more gay sons (10/44=23%). Our findings support a role for the X chromosome in regulating sexual orientation in a subgroup of gay men.

OBJECTIVES: To determine the prevalence and incidence of hepatitis A (HAV) and B (HBV) infection and vaccination in HIV-negative homosexual men in Sydney, and associated risk factors. METHODS: An open prospective cohort study was conducted among a community-based sample of HIV-negative homosexual men in Sydney in 2001-02. Participants underwent a face-to-face interview, regarding demographics, sexual behavioural risk factors and sexually transmitted infections, and blood samples were collected. They were followed annually. RESULTS: Nine hundred and three men completed a baseline interview by the end of 2002. Among them, 68% were seropositive to hepatitis A. The seroprevalence of prior hepatitis B infection was 19%, and 53% had serological evidence of HBV vaccination. Younger men were much more likely to be seronegative, with 48% and 46% of <25-year-olds being seronegative to HAV and HBV respectively. In multivariate analysis HAV and HBV infection were associated with increasing age, greater number of lifetime sex partners and HBV infection was also associated with previous sexually transmitted infections. HAV vaccination was associated with increasing age, greater number of lifetime sex partners, overseas travel in the last year and self-reported anogenital warts. HBV vaccination was associated with higher occupational status, greater lifetime number of sex partners and previous sexually transmitted infections. CONCLUSION: Substantial proportions of gay community-attached young homosexual men are still at risk of HAV and HBV infection. This study points to a need for vaccination strategies which ensure high levels of hepatitis A and B immunity in young sexually active gay men.

X-inactivation is a random process that occurs in females early during embryogenesis. Females are mosaics with an equal proportion of cells with the paternal (Xp) or maternal X-chromosome (Xm) in the active state. However, close to 40% of healthy females aged more than 60 y.o. present a significant skewing of X-inactivation ratios (Xp:Xm >3 :1). The exact etiology of this age-associated skewing (AAS) in blood cells is unknown. We hypothesized that AAS is due to hemizygous cell selection caused by allelic variants in hematopoiesis or cell survival genes. To test this hypothesis, we recruited 700 unrelated healthy females of French Canadian ancestry aged more than 60. We determined X-inactivation ratio at the HUMARA locus. We genotyped 81 different SNPs, using TaqMan technology, in 15 different candidate genes with known role in hematopoiesis, cell cycle, or X-inactivation. Extensive statistical analyses were conducted and demonstrated that none of the 15 candidate genes investigated contribute significantly to AAS.

Autism is a heterogeneous neurodevelopmental disorder with a 3-4 times higher sex ratio in males than females. X chromosome genes may contribute to this higher sex ratio through unusual skewing of X chromosome inactivation. We studied X chromosome skewness in 30 females with classical autism and 35 similarly aged unaffected female siblings as controls using the polymorphic androgen receptor (AR) gene. Significantly, increased X chromosome skewness (e.g.,>80:20%) was detected in our autism group (33%) compared to unaffected females (11%). X chromosome skewness was also seen in 50% of the mothers with autistic daughters. No mutation was seen in the promoter region of the XIST gene reported to be involved in X chromosome inactivation in our subjects. X chromosome skewness has been reported in female carriers of other neurological disorders such as X-linked mental retardation, adrenoleukodystrophy and Rett syndrome.