The genetics of sex differences in brain and behavior

Hippocampal transcriptome reveals novel targets of FASD pathogenesis

INTRODUCTION

Prenatal alcohol exposure can contribute to fetal alcohol spectrum disorders (FASD), characterized by a myriad of developmental impairments affecting behavior and cognition. Studies show that many of these functional impairments are associated with the hippocampus, a structure exhibiting exquisite vulnerability to developmental alcohol exposure and critically implicated in learning and memory; however, mechanisms underlying alcohol-induced hippocampal deficits remain poorly understood. By utilizing a high-throughput RNA-sequencing (RNA-seq) approach to address the neurobiological and molecular basis of prenatal alcohol-induced hippocampal functional deficits, we hypothesized that chronic binge prenatal alcohol exposure alters gene expression and global molecular pathways in the fetal hippocampus.

METHODS

Timed-pregnant Sprague-Dawley rats were randomly assigned to a pair-fed control (PF) or binge alcohol (ALC) treatment group on gestational day (GD) 4. ALC dams acclimatized from GDs 5-10 with a daily treatment of 4.5 g/kg alcohol and subsequently received 6 g/kg on GDs 11-20. PF dams received a once daily maltose dextrin gavage on GDs 5-20, isocalorically matching ALC counterparts. On GD 21, bilateral hippocampi were dissected, flash frozen, and stored at -80° C. Total RNA was then isolated from homogenized tissues. Samples were normalized to ~4nM and pooled equally. Sequencing was performed by Illumina NextSeq 500 on a 75 cycle, single-end sequencing run.

RESULTS

RNA-seq identified 13,388 genes, of these, 76 genes showed a significant difference (p < 0.05, log2 fold change ≥2) in expression between the PF and ALC groups. Forty-nine genes showed sex-dependent dysregulation; IPA analysis showed among female offspring, dysregulated pathways included proline and citrulline biosynthesis, whereas in males, xenobiotic metabolism signaling and alaninine biosynthesis etc. were altered.

CONCLUSION

We conclude that chronic binge alcohol exposure during pregnancy dysregulates fetal hippocampal gene expression in a sex-specific manner. Identification of subtle, transcriptome-level dysregulation in hippocampal molecular pathways offers potential mechanistic insights underlying FASD pathogenesis.

Sex differences in behavior and neuropharmacology of zebrafish

Sex is an important variable in biomedical research. The zebrafish (Danio rerio) is increasingly utilized as a powerful new model organism in translational neuroscience and pharmacology. Mounting evidence indicates important sex differences in zebrafish behavioral and neuropharmacological responses. Here, we discuss the role of sex in zebrafish central nervous system (CNS) models, their molecular mechanisms, recent findings and the existing challenges in this field. We also emphasize the growing utility of zebrafish models in translational neuropharmacological research of sex differences, fostering future CNS drug discovery and the search for novel sex-specific therapies. Finally, we highlight the interplay between sex and environment in zebrafish models of sex-environment correlations as an important strategy of CNS disease modeling using this aquatic organism.

Sex steroid hormone modulation of neural stem cells: a critical review

While numerous in vivo experiments have sought to explore the effects of sex chromosome composition and sex steroid hormones on cellular proliferation and differentiation within the mammalian brain, far fewer studies as reviewed here, have explored these factors using a direct in vitro approach. Generally speaking, in vivo studies provide the gold standard to demonstrate applicable findings in regards to the role hormones play in development. However, in the case of neural stem cell (NSC) biology, there remain many unknown factors that likely contribute to observations made within the developed brain, specifically in regions where there are abundant sex steroid hormone receptors. For these reasons, using a NSC in vitro model may provide a more controlled and refined system to explore the direct effects of sex and hormone response, limiting the vast array of other influences on NSCs occurring during development and within adult cellular niches. These specific cellular models may have the ability to greatly improve the mechanistic understanding of changes occurring within the developing brain during the hormonal organization process, in addition to other modifications that may contribute to neuro-psychiatric sex-biased diseases.

Role of sex in post-transplant diabetes mellitus development: Are men and women equal?

INTRODUCTION

Sex differences are defined as biology-linked differences between women and men that occur through the sex chromosomes and their effects on organ systems.

MATERIAL AND METHODS

The objective of this prospective study was to determine risk factors for post-transplant diabetes mellitus (PTDM) in men and women.

RESULTS

A total of 417 patients (271 men and 146 women) were included in the monitored group. Age at the time of kidney transplantation (KT) >60 years and hypovitaminosis D at the time of KT (<20 μg/l) were identified as independent risk factors for PTDM in both men and women. It was further confirmed as an independent risk factor for men a waist circumference at the time of KT >94 cm, C-peptide at the time of KT >5 ng/ml, HOMA-IR >2 and triacylglycerols at the time of KT >1.7 mmol/l. In case of women, the dominant factor was BMI at the time of KT >30 kg/m2 and menopause at the time of KT. A significant decrease in C-peptide was recorded in women with PTDM.

CONCLUSION

It was confirmed that there are gender differences with regard to the development of PTDM after KT. Women show pancreas β cell dysfunction, whereas insulin resistance and metabolic syndrome are dominant in men.

Characterization of Sex Differences in Ocular Herpes Simplex Virus 1 Infection and Herpes Stromal Keratitis Pathogenesis of Wild-Type and Herpesvirus Entry Mediator Knockout Mice

Sex differences related to immune response and inflammation play a role in the susceptibility and pathogenesis of a variety of viral infections and disease (S. L. Klein, Bioessays 34:1050-1059, 2012, https://doi.org/10.1002/bies.201200099). Herpes simplex virus 1 (HSV-1) causes chronic inflammatory disease in the cornea, an immune-privileged tissue, resulting in irreversible damage and blindness in affected individuals (A. Rowe, A. St Leger, S. Jeon, D. K. Dhaliwal, et al., Prog Retin Eye Res 32:88-101, 2013, https://doi.org/10.1016/j.preteyeres.2012.08.002). Our research focuses on the role of herpesvirus entry mediator (HVEM) as an immune regulator during ocular HSV-1 infection. Mice lacking HVEM (HVEM knockout [KO] mice) exhibit lower levels of immune cell infiltrates and less severe ocular disease in the cornea than wild-type (WT) mice. As sex differences contribute to pathogenesis in many inflammatory diseases, we tested whether sex acts as a biological variable in the immune response to HSV-1 infection and herpes stromal keratitis (HSK) pathogenesis. Adult male and female WT and HVEM KO mice were inoculated with HSV-1 via corneal scarification and monitored daily for disease course. Viral titers were determined, and immune cell infiltrates were collected and analyzed. Our results indicated no significant differences in viral titers in tear film or affected tissues, in immune cell infiltration, or in clinical symptoms between males and females of either genotype. These results suggest that sex is not a significant biological variable in this experimental model and that male and female mice of the C57BL/6 background can be used similarly in studies of ocular HSV-1 pathogenesis.IMPORTANCE Sex hormones have come to be considered an important factor for the development of certain diseases only recently and as such should continue to be considered a biological variable. Ocular HSV-1, and the resulting HSK, is the leading cause of infectious blindness worldwide. We compared levels of ocular HSV-1 infection and pathogenesis in the two sexes and found no significance differences between male and female WT mice or HVEM KO mice.

Identification and analysis of the human sex-biased genes

Tremendous differences between human sexes are universally observed. Therefore, identifying and analyzing the sex-biased genes are becoming basically important for uncovering the mystery of sex differences and personalized medicine. Here, we presented a computational method to identify sex-biased genes from public gene expression databases. We obtained 1407 female-biased genes (FGs) and 1096 male-biased genes (MGs) across 14 different tissues. Bioinformatics analysis revealed that compared with MGs, FGs have higher evolutionary rate, higher single-nucleotide polymorphism density, less homologous gene numbers and smaller phyletic age. FGs have lower expression level, higher tissue specificity and later expressed stage in body development. Moreover, FGs are highly involved in immune-related functions, whereas MGs are more enriched in metabolic process. In addition, cellular network analysis revealed that MGs have higher degree, more cellular activating signaling and tend to be located in cellular inner space, whereas FGs have lower degree, more cellular repressing signaling and tend to be located in cellular outer space. Finally, the identified sex-biased genes and the discovered biological insights together can be a valuable resource helpful for investigating sex-biased physiology and medicine, for example sex-biased disease diagnosis and therapy, which represents one important aspect of personalized and precision medicine.

Sex and gender differences in schizophrenic psychoses-a critical review

Many sex and gender differences in schizophrenic psychoses have been reported, but few have been soundly replicated. A stable finding is the later age of onset in women compared to men. Gender differences in symptomatology, comorbidity, and neurocognition seem to reflect findings in the general population. There is increasing evidence for estrogens being psychoprotective in women and for hypothalamic-pituitary-gonadal dysfunction in both sexes.More methodologically sound, longitudinal, multi-domain, interdisciplinary research investigating both sex (biological) and gender (psychosocial) factors is required to better understand the different pathogenesis and etiologies of schizophrenic psychoses in women and men, thereby leading to better tailored treatments and improved outcomes.

Oxytocin-mediated social enrichment promotes longer telomeres and novelty seeking

The quality of social relationships is a powerful determinant of lifetime health. Here, we explored the impact of social experiences on circulating oxytocin (OT) concentration, telomere length (TL), and novelty-seeking behaviour in male and female rats. Prolonged social housing raised circulating OT levels in both sexes while elongating TL only in females. Novelty-seeking behaviour in females was more responsive to social housing and increased OT levels than males. The OT antagonist (OT ANT) L-366,509 blocked the benefits of social housing in all conditions along with female-specific TL erosion and novelty-seeking deficit. Thus, females seem more susceptible than males to genetic and behavioural changes when the secretion of endogenous OT in response to social life is interrupted. Social enrichment may, therefore, provide a therapeutic avenue to promote stress resiliency and chances of healthy aging across generations.

Hormonal Influences on Cognitive Function

This article examines how hormonal changes may affect the neuronal networking and mechanisms of cognitive function. Hormones are the chemical regulators of the human body and function critically to maintain various processes, such as growth, emotions and even cognition. Numerous studies have examined the relationship between hormonal effects and cognitive function; these studies have investigated different factors, such as aging, pregnancy, post-natal states, emotions and stress. Different types of hormones produce different outcomes for the human body and mind. Hormones may also contribute to both positive and negative outcomes, depending on whether the hormone levels are too low or too high. To investigate the hormonal effects on cognitive function, the sources of localisation must be localised, so that the neuronal network can be realised. Furthermore, cognitive function does not rely on a specific brain region but is determined by the neuronal network interactions. Thus, it is worthwhile to know the neural mechanisms behind cognitive functions that are affected by hormones.

Family environment interacts with CRHR1 rs17689918 to predict mental health and behavioral outcomes

BACKGROUND

Corticotrophin-releasing hormone receptor-1 gene (CRHR1) variants have been implicated in mental health. However, little is known of the effects of CRHR1 on long-term mental health and behavior in presence of environmental stressors. We assess the effects of CRHR1 variant (rs17689918)-by-environment interactions on emotionality and behavioral traits, including anxiety, depression, aggression and antisocial behaviors. We also determine effects of rs17689918-by-environment-by-sex interactions on the above-mentioned outcomes.

METHODS

Genotypic assessments were carried out in 564 children (mean age 10 years, 52.5% females) from the ongoing longitudinal Estonian Children Personality Behaviour and Health Study (ECPBHS). Information on stressful life events and family relationships were available at baseline and information on behavioral and mental health outcomes (self- and parent-reports) were available at follow-up ages of 18 and 25 years. ANOVAs were used to determine associations of two-way CRHR1-by-environment and three-way CRHR1-by-sex-by-environment interactions on behavioral and mental health outcomes.

RESULTS

Two-way CRHR1 interaction effects showed associations between low familial warmth and hostility in individuals with the GG genotype. Associations of low familial warmth with aggression, of higher number of stressful life events with aggression, and of stressful live events with anxious-depressive symptoms were noted in male A-allele carriers and female GG homozygotes.

CONCLUSION

CRHR1-by-familial environment interactions influence both outwardly-directed aggression as well as mood and anxiety disorder symptoms in a sex-specific manner. The type of environmental stressor can also influence effects of CRHR1 on behavioral and mental health outcomes.

Sex: A Significant Risk Factor for Neurodevelopmental and Neurodegenerative Disorders

Males and females sometimes significantly differ in their propensity to develop neurological disorders. Females suffer more from mood disorders such as depression and anxiety, whereas males are more susceptible to deficits in the dopamine system including Parkinson's disease (PD), attention-deficit hyperactivity disorder (ADHD) and autism. Despite this, biological sex is rarely considered when making treatment decisions in neurological disorders. A better understanding of the molecular mechanism(s) underlying sex differences in the healthy and diseased brain will help to devise diagnostic and therapeutic strategies optimal for each sex. Thus, the aim of this review is to discuss the available evidence on sex differences in neuropsychiatric and neurodegenerative disorders regarding prevalence, progression, symptoms and response to therapy. We also discuss the sex-related factors such as gonadal sex hormones and sex chromosome genes and how these might help to explain some of the clinically observed sex differences in these disorders. In particular, we highlight the emerging role of the Y-chromosome gene, SRY, in the male brain and its potential role as a male-specific risk factor for disorders such as PD, autism, and ADHD in many individuals.

Decoding Sex Differences in the Brain, One Worm at a Time

Sex differences in the brain are prominent features across the animal kingdom. Understanding the anatomical and regulatory mechanisms behind these differences is critical for both explaining sexually dimorphic behaviors and developing sex-targeted treatments for neurological disorders. Clinical studies considering sex biases and basic research on animal models have provided much evidence for the existence of sex differences in the brain and, in a larger sense, sexual dimorphisms in the nervous system. However, due to the complexity of structure and dimorphic behaviors, it is yet unclear precisely how neuronal sexual dimorphisms are regulated on a molecular or cellular level. This commentary reviews available tools for investigating sexual dimorphisms using a simple model organism, the roundworm Caenorhabditis elegans ( C. elegans), which enables one to study gene regulation at single-cell resolution with a number of cutting-edge molecular and genetic technologies. I highlight the doublesex/mab-3 family of transcription factors, first discovered in invertebrates, and their roles in a potentially universal regulatory mechanism underlying neuronal sexual dimorphisms. Studies of these transcription factors using C. elegans, fruit flies, and vertebrates will promote our understanding of fundamental mechanisms behind sex differences in the brain.

Sex- and age-associated differences in episodic-like memory and transcriptional regulation of hippocampal steroidogenic enzymes in rats

The aim of this study was to evaluate the episodic-like memory (ELM) and the transcriptional regulation of the enzymes involved in hippocampal allopregnanolone synthesis in young adult and middle-aged male and female rats. Young adult males, but not middle-aged ones, showed a good performance in the ELM task. In contrast, neither young nor middle-aged females were able to discriminate the spatial order in which the objects were presented. In females, aging decreased the transcription of steroidogenic-related genes. In addition, the mRNA levels of 5α-reductase-1 were higher and the methylation of its promoter was lower in young adult females than in males, suggesting an epigenetic control. Further studies are needed to establish correlations between ELM and the transcriptional regulation of hippocampal steroidogenic enzymes. Our results contribute to the knowledge of sex differences in gene expression, methylation and memory during aging.

Sex differences in how inflammation affects behavior: What we can learn from experimental inflammatory models in humans

Human models demonstrate that experimental activation of the innate immune system has profound effects on brain activation and behavior, inducing fatigue, worsened mood and pain sensitivity. It has been proposed that inflammation is a mechanism involved in the etiology and maintenance of depression, chronic pain and long-term fatigue. These diseases show a strong female overrepresentation, suggesting that a better understanding of sex differences in how inflammation drives behavior could help the development of individualized treatment interventions. For this purpose, we here review sex differences in studies using experimental inflammatory models to investigate changes in brain activity and behavior. We suggest a model in which inflammation accentuates sex differences in brain networks and pre-existing vulnerability factors. This effect could render women more vulnerable to the detrimental effects of immune-to-brain communication over time. We call for systematic and large scale investigations of vulnerability factors for women in the behavioral response to inflammation.

Neurobiology of gender identity and sexual orientation

Sexual identity and sexual orientation are independent components of a person's sexual identity. These dimensions are most often in harmony with each other and with an individual's genital sex, although not always. The present review discusses the relationship of sexual identity and sexual orientation to prenatal factors that act to shape the development of the brain and the expression of sexual behaviours in animals and humans. One major influence discussed relates to organisational effects that the early hormone environment exerts on both gender identity and sexual orientation. Evidence that gender identity and sexual orientation are masculinised by prenatal exposure to testosterone and feminised in it absence is drawn from basic research in animals, correlations of biometric indices of androgen exposure and studies of clinical conditions associated with disorders in sexual development. There are, however, important exceptions to this theory that have yet to be resolved. Family and twin studies indicate that genes play a role, although no specific candidate genes have been identified. Evidence that relates to the number of older brothers implicates maternal immune responses as a contributing factor for male sexual orientation. It remains speculative how these influences might relate to each other and interact with postnatal socialisation. Nonetheless, despite the many challenges to research in this area, existing empirical evidence makes it clear that there is a significant biological contribution to the development of an individual's sexual identity and sexual orientation.

The molecular mechanisms of sexual orientation and gender identity

Differences between males and females are widely represented in nature. There are gender differences in phenotypes, personality traits, behaviors and interests, cognitive performance, and proneness to specific diseases. The most marked difference in humans is represented by sexual orientation and core gender identity, the origins of which are still controversial and far from being understood. Debates continue on whether sexual behavior and gender identity are a result of biological (nature) or cultural (nurture) factors, with biology possibly playing a major role. The main goal of this review is to summarize the studies available to date on the biological factors involved in the development of both sexual orientation and gender identity. A systematic search of published evidence was performed using Medline (from January 1948 to June 2017). Review of the relevant literature was based on authors' expertise. Indeed, different studies have documented the possible role and interaction of neuroanatomic, hormonal and genetic factors. The sexual dimorphic brain is considered the anatomical substrate of psychosexual development, on which genes and gonadal hormones may have a shaping effect. In particular, growing evidence shows that prenatal and pubertal sex hormones permanently affect human behavior. In addition, heritability studies have demonstrated a role of genetic components. However, a convincing candidate gene has not been identified. Future studies (e.i. genome wide studies) are needed to better clarify the complex interaction between genes, anatomy and hormonal influences on psychosexual development.

Biological Sex Differences in Depression: A Systematic Review

Depression is the leading cause of disability worldwide, and its prevalence is 2 times higher in women than in men. There is, however, a lack of data on sex-specific pathophysiology of this disorder. The purpose of this systematic review is to identify the biological sex differences found in major depressive disorder (MDD) in studies published in the last 10 years. We conducted a literature search using the Medline, PsycInfo, PubMed, and Web of Science databases, selecting English-language studies that included physiological measures compared by sex in addition to MDD. We identified 20 relevant studies, which consisted primarily of mixed methodology and samples. The reported physiological measures comprised a variety of serum biomarkers, gene mRNA expression, and brain activity. Findings suggest different biological patterns in those with MDD depending on sex. Specifically, women presented higher levels of inflammatory, neurotrophic, and serotonergic markers and a stronger correlation between levels of some inflammatory and neurotrophic factors and the severity of symptoms. This review provides information about possible different biological patterns for women and men with depressive disorder and may have important implications for treatment. Future research should include homogeneous samples; make comparisons based on sex, control sex hormone fluctuations and pharmacological treatment; and use consistent criteria for evaluating psychobiological changes in MDD.

Sex-dependent impact of different degrees of maternal separation experience on OFT behavioral performances after adult chronic unpredictable mild stress exposure in rats

Early-life social-environmental factors are important for normal development, and different degrees of early-life stress experience have different impacts on adult behaviors and stress responsiveness. The aim of present study was to investigate the long-term effects of different degrees of maternal separation (MS) on male and female rats and subsequent responsiveness to chronic unpredictable mild stress (CUMS) exposure in adults. Sprague-Dawley (SD) newborn pups were exposed to either 15 min/day of MS (MS15), 360 min/day of MS (MS360) or no separation (NS) during postnatal day (PND)4-PND10. At PND56, behavioral tasks, including sucrose preference test (SPT), forced swimming test (FST) and open field test (OFT), were used to explore depressive and anxiety-like behaviors. Then the rats received a series of CUMS for 28 days, behavioral tasks were recorded after CUMS. Prior to CUMS, the behavioral performances in male and female rats were consistent, MS360 led to increased immobile time in FST and decreased activity in OFT, while MS15 rats exhibited behavioral performances similar to NS group. After CUMS, sexual dimorphism was observed in the OFT behavioral responses to adult stress re-exposure, but no differences in FST were observed. CUMS male rats with MS360 experiences showed the worst behavioral performances in OFT compared to those of the other male rats groups, while CUMS female rats without MS experience showed the worst behavioral performances in OFT compared to those of the other female rats groups. Both CUMS male and female rats with MS15 experiences showed better trend in OFT performances than those of CUMS rats with MS360 experience and without MS experiences. These results suggest that brief MS experiences increase the OFT behavioral resilience of rats to adult stress re-exposure, and prolonged MS promotes OFT behavioral resilience of female rats to adult stress re-exposure, while increases vulnerability of male rats to adult stress re-exposure.

The Gendered Family Process Model: An Integrative Framework of Gender in the Family

This article reviews and integrates research on gender-related biological, cognitive, and social processes that take place in or between family members, resulting in a newly developed gendered family process (GFP) model. The GFP model serves as a guiding framework for research on gender in the family context, calling for the integration of biological, social, and cognitive factors. Biological factors in the model are prenatal, postnatal, and pubertal androgen levels of children and parents, and genetic effects on parent and child gendered behavior. Social factors are family sex composition (i.e., parent sex, sexual orientation, marriage status, sibling sex composition) and parental gender socialization, such as modeling, gender-differentiated parenting, and gender talk. Cognitive factors are implicit and explicit gender-role cognitions of parents and children. Our review and the GFP model confirm that gender is an important organizer of family processes, but also highlight that much is still unclear about the mechanisms underlying gender-related processes within the family context. Therefore, we stress the need for (1) longitudinal studies that take into account the complex bidirectional relationship between parent and child gendered behavior and cognitions, in which within-family comparisons (comparing behavior of parents toward a boy and a girl in the same family) are made instead of between-family comparisons (comparing parenting between all-boy families and all-girl families, or between mixed-gender families and same-gender families), (2) experimental studies on the influence of testosterone on human gender development, (3) studies examining the interplay between biology with gender socialization and gender-role cognitions in humans.

Gender Differences in Laser Acupuncture-Results of a Crossover Study with Green and Yellow Laser at the Ear Point Shenmen

Background: One of the most commonly used auricular acupuncture points selected for different pain treatment regimens is Shenmen. This point on the ear has been recognized as having a wide number of applications, as found by scientific investigation. Methods: Within this crossover study, the ear acupoint Shenmen was stimulated with two different kinds of laser (green, 532 nm and yellow, 589 nm) in 22 healthy volunteers (13 female, 9 male; mean age ± SD = 25.3 ± 4.1 years; range 21-36 years). Both green and yellow lasers were used for 15 min in the same volunteers in two different sessions. Results: The most prominent finding was that systolic blood pressure decreased significantly (p = 0.048) after yellow laser stimulation. Heart rate also decreased significantly (p < 0.001), whereas heart rate variability ratio low frequency (LF)/high frequency (HF) (p < 0.001) increased. The effects were significantly more pronounced in females than in males. In addition, the temperature was measured, and temperature increases were demonstrated at different locations on the ear using imaging methods. Conclusions: This study shows evidence of the effect of auricular laser acupuncture. However, a comparison with other publications was impossible because this is the first study using green and yellow laser stimulation on the ear.

Developmental and sex differences in tetramethylenedisulfotetramine (TMDT)-induced syndrome in rats

Tetramethylenedisulfotetramine (TMDT) is a synthetic neurotoxic rodenticide considered a chemical threat agent. Symptoms of intoxication include seizures leading to status epilepticus and death. While children and women have been often the victims, no studies exist investigating the neurotoxic effects of TMDT in developing individuals or females. Thus, we performed such an investigation in developing Sprague-Dawley rats of both sexes in order to identify potential age- or sex-dependent vulnerability to TMDT exposure. Subcutaneous injection was chosen as the preferred route of TMDT exposure. EEG recordings confirmed the seizure activity observed in both postnatal day 15 (P15) and adult rats. Additionally, P15 rats displayed greater sensitivity to TMDT than postnanatal day 25 or adult animals. Seizures were generally more severe in females compared to males. Barrel rotations accompanied convulsions in P25 and adult, but sparsely in P15 rats. Adults developed barrel rolling less frequently than P25 population. Neuronal cell death was not present in 24-h TMDT survivors at any age or sex tested. A seizure rechallenge with flurothyl 7 days following TMDT exposure demonstrated longer latencies to the first clonic seizure but a faster progression into the tonic-clonic seizure in P15 and adult survivors as compared to their vehicle-injected counterparts. In conclusion, the youngest age group represents the most vulnerable population to the TMDT-induced toxidrome. Females appear to be more vulnerable than males. TMDT exposure promotes seizure spread and progression in survivors. These findings will help to establish sex- and age-specific treatment strategies for TMDT-exposed individuals. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 78: 403-416, 2018.

Uncovering neurodevelopmental windows of susceptibility to manganese exposure using dentine microspatial analyses

BACKGROUND

Associations between manganese (Mn) and neurodevelopment may depend on dose and exposure timing, but most studies cannot measure exposure variability over time well.

OBJECTIVE

We apply temporally informative tooth-matrix biomarkers to uncover windows of susceptibility in early life when Mn is associated with visual motor ability in childhood. We also explore effect modification by lead (Pb) and child sex.

METHODS

Participants were drawn from the ELEMENT (Early Life Exposures in MExico and NeuroToxicology) longitudinal birth cohort studies. We reconstructed dose and timing of prenatal and early postnatal Mn and Pb exposures for 138 children by analyzing deciduous teeth using laser ablation-inductively coupled plasma-mass spectrometry. Neurodevelopment was assessed between 6 and 16 years of age using the Wide Range Assessment of Visual Motor Abilities (WRAVMA). Mn associations with total WRAVMA scores and subscales were estimated with multivariable generalized additive mixed models. We examined Mn interactions with Pb and child sex in stratified models.

RESULTS

Levels of dentine Mn were highest in the second trimester and declined steeply over the prenatal period, with a slower rate of decline after birth. Mn was positively associated with visual spatial and total WRAVMA scores in the second trimester, among children with lower (< median) tooth Pb levels: one standard deviation (SD) increase in ln-transformed dentine Mn at 150 days before birth was associated with a 0.15 [95% CI: 0.04, 0.26] SD increase in total score. This positive association was not observed at high Pb levels. In contrast to the prenatal period, significant negative associations were found in the postnatal period from ~ 6 to 12 months of age, among boys only: one SD increase in ln-transformed dentine Mn was associated with a 0.11 [95% CI: - 0.001, - 0.22] to 0.16 [95% CI: - 0.04, - 0.28] SD decrease in visual spatial score.

CONCLUSIONS

Using tooth-matrix biomarkers with fine scale temporal profiles of exposure, we found discrete developmental windows in which Mn was associated with visual-spatial abilities. Our results suggest that Mn associations are driven in large part by exposure timing, with beneficial effects found for prenatal levels and toxic effects found for postnatal levels.

Is human brain masculinization estrogen receptor-mediated? Reply to Luoto and Rantala

Human genetic males are unlike rodent males in that neither the ability to convert testosterone to estrogen nor a functional estrogen receptor (ER) appears necessary for male-typical behavior, but a functional androgen receptor (AR) is required. Brain masculinization is probably mainly AR-mediated in human genetic males. ER binding may nevertheless have important masculinizing or defeminizing effects in human genetic females. Probably the strongest available evidence on this issue is derived from females exposed to synthetic estrogens in utero due to their mother's treatment with DES. As we review, the totality of evidence from this population indicates little or no effect of estrogens on sexuality in genetic females. In addition, if brain masculinization were ER-mediated in humans, it seems unlikely that sex hormone-binding globulin would bind estrogens so effectively as to prevent them from masculinizing the brain. In sum, current evidence suggests that estrogen plays a limited role in masculinizing the human brain and behavior.

Systematic Observation: Relevance of This Approach in Preschool Executive Function Assessment and Association with Later Academic Skills

Executive functions (EFs) are high-level cognitive processes that allow us to coordinate our actions, thoughts, and emotions, enabling us to perform complex tasks. An increasing number of studies have highlighted the role of EFs in building a solid foundation for subsequent development and learning and shown that EFs are associated with good adjustment and academic skills. The main objective of this study was to analyze whether EF levels in 44 Spanish children in the last year of preschool were associated with levels of literacy and math skills the following year, that is, in the first year of compulsory education. We used a multi-method design, which consisted of systematic observation to observe preschool children during play and selective methodology to assess their reading, writing, and math skills in the first year of compulsory primary education. General linear modeling was used to estimate the percentage of variability in academic skills in the first year of primary school that was explained by preschool EF abilities. The results showed that preschool EF level, together with participants and the instrument used to assess academic skills, explained 99% of the variance of subsequent academic performance. Another objective was to determine whether our findings were generalizable to the reference population. To make this determination, we estimated the optimal sample size for assessing preschool EFs. To do this, we performed a generalizability analysis. The resulting generalizability coefficient showed that our sample of 44 students was sufficient for assessing preschool EFs. Therefore, our results are generalizable to the reference population. Our results are consistent with previous reports that preschool EF abilities may be associated with subsequent literacy and math skills. Early assessment of EFs may therefore contribute to identifying children who are likely to experience later learning difficulties and guide the design of suitable interventions for the optimization of EFs.

Effects of chromosomal sex and hormonal influences on shaping sex differences in brain and behavior: Lessons from cases of disorders of sex development

Sex differences in brain development and postnatal behavior are determined largely by genetic sex and in utero gonadal hormone secretions. In humans however, determining the weight that each of these factors contributes remains a challenge because social influences should also be considered. Cases of disorders of sex development (DSD) provide unique insight into how mutations in genes responsible for gonadal formation can perturb the subsequent developmental hormonal milieu and elicit changes in normal human brain maturation. Specific forms of DSDs such as complete androgen insensitivity syndrome (CAIS), congenital adrenal hyperplasia (CAH), and 5α-reductase deficiency syndrome have variable effects between males and females, and the developmental outcomes of such conditions are largely dependent on sex chromosome composition. Medical and psychological works focused on CAH, CAIS, and 5α-reductase deficiency have helped form the foundation for understanding the roles of genetic and hormonal factors necessary for guiding human brain development. Here we highlight how the three aforementioned DSDs contribute to brain and behavioral phenotypes that can uniquely affect 46,XY and 46,XX individuals in dramatically different fashions. © 2016 Wiley Periodicals, Inc.

Preventing harmful effects of epileptic seizures on cerebrovascular functions in newborn pigs: does sex matter?

BackgroundThe potential contribution of sex-related variables to cerebrovascular functions in neonates remains elusive. Newborn piglets provide a translationally relevant model for studying the effects of seizures in the neonatal brain. The present study investigated whether sex differences contribute to cerebrovascular functions in healthy and epileptic newborn pigs.MethodsEpileptic seizures were induced in female and male newborn pigs by bicuculline. An antioxidant drug, the carbon monoxide-releasing molecule CORM-A1, was administered enterally before or during seizures. The responses of pial arterioles to endothelium-, astrocyte-, and vascular smooth muscle-dependent vasodilators were tested in intact and 48-h postictal piglets using the cranial window technique.ResultsIn intact newborn pigs, we did not observe any sex-related differences in cerebrovascular functions. In the postictal male and female newborn pigs, a marked reduction in responses of pial arterioles to endothelium- and astrocyte-dependent vasodilators was detected. CORM-A1, administered before or during seizures, greatly improved the outcome of seizures on cerebrovascular functions in both male and female piglets.ConclusionWe found no evidence of sex-related differences in cerebral vasodilator functions in control and epileptic newborn pigs. In both male and female newborns, epileptic seizures lead to prolonged cerebral vascular dysfunction that is effectively prevented by CORM-A1 therapy.

Post-Traumatic Stress Disorder Symptomatology in People affected by Home Eviction in Spain

Despite the higher proportion of foreclosures and home evictions executed in Spain, compared to other countries, and the known link between social exclusion and mental health problems, studies exploring this association in Spain remain scarce. This study investigated the link between the process of home eviction and the appearance of symptomatology of post-traumatic stress disorder (PTSD), anxiety, depression, and perceived stress. Two hundred and five people affected by the process of home eviction were assessed using a structured interview that included three validated assessment instruments for PTSD, perceived stress, anxiety and depression. Analysis involved comparison with the normative groups that formed the validation studies together with regression analysis to determine the major psychological and socio-demographic predictors of perceived stress. Of the participants, 95.1% reported that they were experiencing the process of home eviction with fear, helplessness, or horror. In PTSD symptomatology, they scored higher than the normative PTSD group in symptoms of avoidance (t = 5.01; p < .05), activation (t = 5.48; p < .01), and total score (t = 4.15; p < .05). Of this subgroup, 72.5% fulfilled the DSM-IV symptom criteria for PTSD. The major predictor of perceived stress was PTSD symptomatology (B = .09; p < .001). The process of home eviction in Spain is having an alarming impact on mental health of affected people calling for effective measures to provide psychological and social support.

Sex influences in neurological disorders: case studies and perspectives

Beginning in the late 1980s and early 1990s, scientists and the public alike recognized that, for too long, women had been underrepresented in clinical trials. While much progress was made in the following decades, preclinical research still often ignores sex as a fundamental biological variable. Many neurological disorders, including multiple sclerosis and migraine, show strong sex differences in incidence and disease manifestation. In this commentary, we highlight case studies of neurological disorders affecting men and women to demonstrate the need for more such studies. Research conducted in these areas so far has shed light on the underlying mechanisms of the disease and offers the promise to help develop more personalized treatments for both men and women.

Low dose radiation effects on the brain - from mechanisms and behavioral outcomes to mitigation strategies

Based on the most recent estimates by the Canadian Cancer Society, 2 in 5 Canadians will develop cancer in their lifetimes. More than half of all cancer patients receive some type of radiation therapy, and all patients undergo radiation-based diagnostics. While radiation is one of the most important diagnostic and treatments modalities, high-dose cranial radiation therapy causes numerous central nervous system side-effects, including declines in cognitive function, memory, and attention. While the mechanisms of these effects have been studies, they still need to be further elucidated. On the other hand, the effects of low dose radiation as well as indirect radiation bystander effects on the brain remain elusive. We pioneered analysis of the molecular and cellular effects of low dose direct, bystander and scatter radiation on the brain. Using a rat model, we showed that low dose radiation exposures cause molecular and cellular changes in the brain and impacts animal behavior. Here we reflect upon our recent findings and current state of knowledge in the field, and suggest novel radiation effect biomarkers and means of prevention. We propose strategies and interventions to prevent and mitigate radiation effects on the brain.

Association of cognitive function and liability to addiction with childhood herpesvirus infections: A prospective cohort study

Liability to substance use disorder (SUD) is largely nonspecific to particular drugs and is related to behavior dysregulation, including reduced cognitive control. Recent data suggest that cognitive mechanisms may be influenced by exposure to neurotropic infections, such as human herpesviruses. In this study, serological evidence of exposure to human herpesvirus Herpes simplex virus Type 1 (HSV-1), cytomegalovirus (CMV), and Epstein-Barr virus (EBV) as well as Toxoplasma gondii was determined in childhood (age ~11 years) in 395 sons and 174 daughters of fathers with or without SUD. Its relationships with a cognitive characteristic (IQ) in childhood and with risk for SUD in adulthood were examined using correlation, regression, survival, and path analyses. Exposure to HSV-1, EBV, and T. gondii in males and females, and CMV in males, was associated with lower IQ. Independent of that relationship, EBV in females and possibly in males, and CMV and possibly HSV-1 in females were associated with elevated risk for SUD. Therefore, childhood neurotropic infections may influence cognitive development and risk for behavior disorders such as SUD. The results may point to new avenues for alleviating cognitive impairment and SUD risk.

Disruption of aromatase homeostasis as the cause of a multiplicity of ailments: A comprehensive review

Human health is beset with a legion of ailments, which is exacerbated by lifestyle errors. Out of the numerous enzymes in human body, aromatase, a cytochrome P450 enzyme is particularly very critical. Occurring at the crossroads of multiple signalling pathways, its homeostasis is vital for optimal health. Unfortunately, medications, hormone therapy, chemical additives in food, and endocrine-disrupting personal care products are oscillating the aromatase concentration beyond the permissible level. As this enzyme converts androgens (C19) into estrogens (C18), its agitation has different outcomes in different genders and age groups. Some common pathologies associated with aromatase disruption include breast cancer, prostate cancer, polycystic ovary syndrome (PCOS), endometriosis, osteoporosis, ovarian cancer, gastric cancer, pituitary cancer, Alzheimer's disease, schizophrenia, male hypogonadism, and transgender issues. Several drugs, cosmetics and pesticides act as the activators and suppressors of this enzyme. This carefully-compiled critical review is expected to increase public awareness regarding the threats resultant of the perturbations of this enzyme and to motivate researchers for further investigation of this field.

Birth order and recalled childhood gender nonconformity in Samoan men and fa'afafine

Having a greater than average number of older biological brothers is a robust correlate of male androphilia (i.e., sexual attraction and arousal to adult males). Previous investigations have sought to understand whether this fraternal birth order (FBO) effect is also systematically related to recalled indicators of childhood gender nonconformity (CGN). However, these investigations have relied on data from low-fertility Western populations in which expressions of femininity in male children are routinely stigmatized and consequently, suppressed. The present study examined the FBO effect (among other sibship characteristics) and recalled indicators of CGN in Samoa, a high-fertility population, whose members are relatively tolerant of male femininity. Indeed, Samoans identify feminine androphilic males as belonging to an alternative gender category, known locally as fa'afafine. The present study compared the sibship characteristics of 231 fa'afafine and 231 opposite-sex attracted men from Samoa, as well as how these characteristics related to recalled CGN. Results replicated the well-established FBO effect for predicting male sexual orientation, with each older brother increasing the odds of being androphilic by 21%. However, no relationship was found between the number of older brothers (or other siblings) a participant had and their recalled CGN. Although fa'afafine reported significantly more CGN than Samoan men, CGN did not mediate the FBO effect, nor did the FBO effect and CGN interact to predict male sexual orientation. These findings are consistent with previous studies suggesting that the FBO effect is associated with male sexual orientation, but not childhood female-typical gender expression among androphilic males.

Patterns of age related changes for phosphodiesterase type-10A in comparison with dopamine D2/3 receptors and sub-cortical volumes in the human basal ganglia: A PET study with 18F-MNI-659 and 11C-raclopride with correction for partial volume effect

Phosphodiesterase 10A enzyme (PDE10A) is an important striatal target that has been shown to be affected in patients with neurodegenerative disorders, particularly Huntington´s disease (HD). PDE10A is expressed on striatal neurones in basal ganglia where other known molecular targets are enriched such as dopamine D_2/3 receptors (D_2/3 R). The aim of this study was to examine the availability of PDE10A enzyme in relation with age and gender and to compare those changes with those related to D_2/3 R and volumes in different regions of the basal ganglia. As a secondary objective we examined the relative distribution of D_2/3 R and PDE10A enzyme in the striatum and globus pallidus. Forty control subjects (20F/20M; age: 44±11y, age range 27-69) from an ongoing positron emission tomography (PET) study in HD gene expansion carriers were included. Subjects were examined with PET using the high-resolution research tomograph (HRRT) and with 3T magnetic resonance imaging (MRI). The PDE10A radioligand ¹⁸F-MNI-659 and D_2/3 R radioligand ¹¹C-raclopride were used. The outcome measure was the binding potential (BP_ND) estimated with the two-tissue compartment model (¹⁸F-MNI-659) and the simplified reference tissue model (¹¹C-raclopride) using the cerebellum as reference region. The PET data were corrected for partial volume effects. In the striatum, PDE10A availability showed a significant age-related decline that was larger compared to the age-related decline of D_2/3 R availability and to the age-related decline of volumes measured with MRI. In the globus pallidus, a less pronounced decline of PDE10A availability was observed, whereas D_2/3 R availability and volumes seemed to be rather stable with aging. The distribution of the PDE10A enzyme was different from the distribution of D_2/3 R, with higher availability in the globus pallidus. These results indicate that aging is associated with a considerable physiological reduction of the availability of PDE10A enzyme in the striatum. Moreover as result of the analysis, in the striatum for both the molecular targets, we observed a gender effect with higher BP_ND the female group.

Handedness is a biomarker of variation in anal sex role behavior and Recalled Childhood Gender Nonconformity among gay men

Developmental theories of the biological basis of sexual orientation suggest that sexually differentiated psychological and behavioural traits should be linked with sexual orientation. Subgroups of gay men delineated by anal sex roles differ according to at least one such trait: gender expression. The present study assessed the hypothesis that handedness, a biologically determined sexually differentiated trait, corresponds to differences in subgroups of gay men based on anal sex role. Furthermore, it assessed whether handedness mediates the association between gender nonconformity and male sexual orientation. Straight and gay men (N = 333) completed the Edinburgh Inventory of Handedness and the Recalled Childhood Gender Nonconformity Scale. Gay men also completed measures of anal sex role preference. As in previous studies, gay men showed greater non-right-handedness and gender nonconformity than straight men. Also, among gay men, bottoms/versatiles (i.e., gay men who take a receptive anal sex role, or who take on both a receptive and insertive anal sex role) were more gender-nonconforming than tops (i.e., gay men who take an insertive anal sex role). In support of the hypothesis, bottoms/versatiles were more non-right-handed than tops and handedness mediated the male sexual orientation and anal sex role differences in Recalled Childhood Gender Nonconformity. Together, these findings suggest that developmental processes linked to handedness underpin variation among men in sexual orientation and gender nonconformity as well as variation among subgroups of gay men that are delineated by anal sex roles.

Cognitive performance of male and female C57BL/6J mice after repetitive concussive brain injuries

In contact sports, repetitive concussive brain injury (rCBI) is the prevalent form of head injury seen in athletes. The need for effective treatment is urgent as rCBI has been associated with a host of cognitive, behavioral and neurological complaints. There has been a growing trend in the use of female animals in pre-clinical research, but few studies have investigated possible sex differences following rCBI. The goal of the current study was to determine any differences between male and female C57BL/6J mice on assessments of learning and memory after repetitive concussive injury. Following rCBI by impact to the scalp, male mice exhibited longer righting reflexes during acute recovery. In both sexes, there were no evident histopathological changes observed in the underlying cerebral cortex or hippocampus. Reactive astrogliosis was elevated in the corpus callosum and optic tract, and astrogliosis was slightly less in the optic tract of female mice. rCBI mice exhibited impairment during the learning phase of the Morris water maze (MWM), but female mice, in comparison to male mice, were observed to have superior spatial memory during standard MWM probe trials. Female mice were overall more active, evidenced by greater distances traveled in the y-maze and greater swim speeds in the MWM. The results of this study demonstrate sex differences in cognitive performance following rCBI and support previous research suggesting the neuroprotective role of sex in brain injury.

Selection and evaluation of reference genes for analysis of mouse (Mus musculus) sex-dimorphic brain development

The development of the brain is sex-dimorphic, and as a result so are many neurological disorders. One approach for studying sex-dimorphic brain development is to measure gene expression in biological samples using RT-qPCR. However, the accuracy and consistency of this technique relies on the reference gene(s) selected. We analyzed the expression of ten reference genes in male and female samples over three stages of brain development, using popular algorithms NormFinder, GeNorm and Bestkeeper. The top ranked reference genes at each time point were further used to quantify gene expression of three sex-dimorphic genes (Wnt10b, Xist and CYP7B1). When comparing gene expression between the sexes expression at specific time points the best reference gene combinations are: Sdha/Pgk1 at E11.5, RpL38/Sdha E12.5, and Actb/RpL37 at E15.5. When studying expression across time, the ideal reference gene(s) differs with sex. For XY samples a combination of Actb/Sdha. In contrast, when studying gene expression across developmental stage with XX samples, Sdha/Gapdh were the top reference genes. Our results identify the best combination of two reference genes when studying male and female brain development, and emphasize the importance of selecting the correct reference genes for comparisons between developmental stages.

Effects of a Home-Based Family-Centred Early Habilitation Program on Neurobehavioural Outcomes of Very Preterm Born Infants: A Retrospective Cohort Study

Preterm children have an increased risk of neurodevelopmental impairments which include psychomotor and language retardation. The objectives of the present retrospective cohort study were to examine the effects of an individually adapted, home-based, and family-centred early developmental habilitation program on neurodevelopmental and behavioural outcomes of very preterm children compared with a standard follow-up at 2 years' corrected age. Enrolled infants were retrospectively assigned to the intervention group (61 subjects) or to the control group (62 subjects) depending on whether they had or had not carried out a home-based family-centred early developmental habilitation program focused on environmental enrichment, parent-guided environmental interaction, and infant development. Developmental outcome was assessed for both groups at 24 months' corrected age using the Bayley Scales of Infant Development 2nd Edition. Intervention significantly improved both cognitive and behavioural outcomes. In addition, males had significantly lower scores than females either before or after treatment. However, the treatment was effective in both genders to the same extent. In conclusion, a timely updated environment suitable to the infant's developmental needs could provide the best substrate where the parent-infant relationship can be practised with the ultimate goal of achieving further developmental steps.

Pubertal Stress and Nutrition and their Association with Sexual Orientation and Height in the Add Health Data

A number of studies have indicated that gay men tend to be shorter, on average, than heterosexual men. Less evidence exists that lesbian women are taller, on average, than heterosexual women. The most popular explanation of the association between sexual orientation and height involves prenatal factors, such that, for example, gay men may have been exposed to lower than typical androgens during fetal development, which impacts their height and sexual orientation as adults. An alternative explanation involves stress, given that stress has been associated with sexual minority identification and with lower height. Another alternative explanation involves nutrition, although its relationship is less clear with sexual minority identification. Using the Add Health data, which is a large, nationally representative and longitudinal sample of American adolescents (n = 14,786), we tested a mediation model, such that sexual orientation → pubertal stress/nutrition → height. Within men, we found that gay men (n = 126) were shorter, on average, than heterosexual men (n = 6412). None of the 24 pubertal stress-related and 15 pubertal nutrition-related variables assessed in the Add Health data mediated the relationship between sexual orientation and height in men. Within women, lesbians (n = 75) did not differ significantly in stature compared to heterosexual women (n = 6267). Thus, prenatal mechanisms (e.g., hormones, maternal immune response) are likely better candidates for explaining the height difference between gay men and heterosexual men.

Gay Male Only-Children: Evidence for Low Birth Weight and High Maternal Miscarriage Rates

Recent findings suggest that there may be a maternal immune response underpinning the etiology of sexual orientation of gay male only-children. This maternal immune response appears to be distinct from that which is purported to explain the classic fraternal birth order effect found in studies of male sexual orientation. We tested two predictions related to the hypothesized maternal immune response in mothers of gay male only-children: (1) elevated fetal loss among mothers who have had gay male only-children and (2) lower birth weight in gay male only-children. Mothers of at least one gay son (n = 54) and mothers of heterosexual son(s) (n = 72) self-reported their pregnancy histories, including the birth weights of newborns and number of fetal losses (e.g., miscarriages). Mothers of gay male only-children (n = 8) reported significantly greater fetal loss compared with mothers of males with four other sibship compositions (gay with no older brothers, gay with older brothers, heterosexual only-children, heterosexual with siblings) (n = 118). Also, firstborn gay male only-children (n = 4) had a significantly lower birth weight than firstborn children in the four other sibship compositions (n = 59). Duration of pregnancy was not significantly different among the groups of firstborn children in the birth weight analyses. Thus, this study found further support for a distinct pattern of maternal immune response implicated in the etiology of male sexual orientation. Mechanisms that may underlie this potential second type of maternal immune response are discussed.

Sexual Orientation, Objective Height, and Self-Reported Height

Studies that have used mostly self-reported height have found that androphilic men and women are shorter than gynephilic men and women, respectively. This study examined whether an objective height difference exists or whether a psychosocial account (e.g., distortion of self-reports) may explain these putative height differences. A total of 863 participants, recruited at a Canadian university, the surrounding region, and through lesbian, gay, bisexual, and transgender (LGBT) events across Canada, self-reported their height and had their height measured. Androphilic men were shorter, on average, than gynephilic men. There was no objective height difference between gynephilic, ambiphilic, and androphilic women. Self-reported height, statistically controlling for objective height, was not related to sexual orientation. These findings are the first to show an objective height difference between androphilic and gynephilic men. Also, the findings suggest that previous studies using self-reported height found part of a true objective height difference between androphilic and gynephilic men. These findings have implications for existing biological theories of men's sexual orientation development.